Colorado Gardening Calendar for December 2023

By Molly Gaines, CSU Extension-Denver Master Gardener since 2019

Grasses left uncut provide great visual appeal throughout the winter months. Photo: Molly Gaines

A few snowfalls have already blanketed Denver, making old man winter feel official. This, and the fact that the holiday season is upon us, probably means garden to-dos are not top-of-mind for you. Yet, there are still some important tasks to consider, along with a handful of indoor activities, as we head into these darker days and colder months.

December’s Checklist 

Trees, Shrubs and Perennials 

• When there is no snow cover to provide trees, shrubs and perennials moisture, it’s imperative to their short- and long-term health to water them one to two times monthly. Here’s a great fact sheet from CSU with helpful guidelines for fall and winter watering.
• If you haven’t wrapped the tree trunks of newly planted trees, don’t forget this critical task. They need it for the first few years, until their bark develops texture. For more on this, visit this helpful article from North Dakota State University’s extension office. 
• When the snow falls heavily, shake snow from bent tree limbs and branches. This will avoid breakage. As needed, lightly prune broken limbs to avoid further damage.
• Add mulch to spots where it’s thin in your garden beds. This will help plants retain moisture and protect them from harsh winter winds and freeze/thaw cycles.

Sunflower still standing. Photo: Molly Gaines

Compost

• Yard waste, such as broken branches, and other remaining garden debris can be placed into your city compost bin. If you have a backyard compost bin or pile, continue adding brown and green materials, breaking larger debris into smaller pieces. These items will continue decomposing in the winter months, albeit at a slower pace. In Colorado, it’s best not to turn compost after December, according to this PlantTalk Colorado fact sheet on composting. Turning allows valuable heat to escape, and may stop processing in cold weather. To restart active processing, turn and mix in fresh materials with the winter compost. 

House Plants 

• Winter is the dormant season for non-blooming indoor plants. Reduce watering, stop fertilizing, and keep them away from drafts for the next few months.
• Increase humidity around your plants. Ignore misting with a spray bottle; for this to be effective, you’d need to mist for hours on end. Instead, group plants together on a pebble-lined tray and add water to just below the top of the pebbles.
• Check plants regularly for pests such as mealy bugs and spider mites. If present, treat and quarantine the infected plant. Find remedies here.  

Amaryllis adds a festive flair in December into late January. This trio should produce showy red blooms. Photo: Molly Gaines

Paperwhites take 4-6 weeks to bloom. Start them now for blooms in the new year. Photo: Molly Gaines

Speaking of house plants, ’tis the season for live Christmas trees and holiday plants. Here are some links to keep all of these at their best: Keeping the Ho Ho Ho in Holiday Plants, Tips for Caring for Your Christmas Tree, A Year in the Life of an Amaryllis, and Christmas Cactus Care. 

Holiday plants you may wish to consider for your home, or as a gift to others, include Christmas cactus, poinsettias, amaryllis or even paper whites. I’ve made it a tradition to send my mom a set of amaryllis (pictured above) each December so she can watch it grow through the holidays. Christmas cactus, which can be passed down for many years, can live to be 100 years old! They bloom in the winter and despite being cacti, need regular watering. Poinsettias add a beautiful pop of red, white or pink during the holidays and beyond. Their large size can make them a dramatic focal point of a room. 

Thank you for reading our blog. We’ll be back with one more post in December before wrapping up 2023. In the meantime, we wish you a beautiful, joyous start to your holiday season!

 As always, CSU is available in every season with gardening advice at the CSU Extension Yard and Garden website.

Colorado Gardening Calendar for November 2023

By Molly Gaines, CSU Extension – Denver Master Gardener since 2019

If you haven’t already, it’s time to clean out your garden beds. Photo: Molly Gaines

Right on time, we’ve had our first freeze and snow here in Denver. Yet my garden still sits, hanging on for dear life, in desperate need of clearing, composting, amending and mulching. I guess I’ve been in denial, holding on to my fading zinnias and still-green tomatoes, enjoying this gorgeous fall with its warm temperatures and prolonged tree color. Luckily, November is still likely to bring a few mild days. So now’s the time to make a list and check the boxes before everything goes into hibernation until next spring.

A Gardener’s Yard and Garden Checklist for November 

Vegetable Garden

• Clear all plantings and compost. Pests and diseases can overwinter in plant debris and wreak havoc on next year’s garden (aphids, anyone?). 
• Oh my do I have a lot of green tomatoes, around 40 at last count. If you’ve been covering plants to extend the season, it’s time for your final harvest. For ideas on storing late-season produce, visit this helpful page from the University of Minnesota’s Extension office. For a fun recipe from Martha Stewart on cooking green tomatoes, visit here.  
• Spread and work compost into your garden beds before the ground freezes. 

Harvest any remaining vegetables that were lucky to survive the initial frosts. Photo: Molly Gaines

Trees and Shrubs

• Remove dead tree branches, including those on shrubs and roses. 
• Water new fall plantings weekly, including trees, and other perennials until the ground freezes. It’s important to water throughout the winter during warm, dry periods to support healthy roots and next year’s growth. 
• Wrap the trunks of young trees to prevent sunscald, which can occur during periods of alternate warming and freezing in the winter. “On at Thanksgiving, off on tax day” is a good rule of thumb for utilizing tree wrap.
• Protect evergreens with burlap plant bags to prevent them from drying out. 

Lawn Care 

• Fertilize a final time; in Denver this can be done up until Thanksgiving. For more information about fall lawn fertilization from PlantTalk Colorado, visit here. 
• It’s time to blow out and shut off irrigation if you haven’t already. Rake up leaves and either compost or mow over them for garden bed mulch.

Perennial Beds 

• If you haven’t cut back grasses and flowering perennials for the year, let them be. Dead plant stems and leaves provide habitat for moths, beneficial garden insects and butterflies that overwinter.
• Continue watering until the ground freezes. This is especially important for all new plantings. 
• As long as the soil is workable, plant bulbs for spring flowers in the next few weeks. They should still have time to establish before the ground freezes. Water in well. 
• Dig up and save dahlia tubers. Allow them to harden off for two weeks after frost before storing. Find directions here.

Other Projects 

• Bring indoors any houseplants or other potted plants you’d like to save. Hopefully, they’ve survived under heavy protection so far.
• Sanitize, sharpen, and oil tools, including the lawnmower blade. Come spring, you’ll be grateful these tools are ready to go. 

Hope it’s not too late to get houseplants indoors! Photo: Molly Gaines

Follow Up: Denver’s Tree Canopy Survey 

The City of Denver published the results of the September survey of residents about Denver’s tree canopy — and the future of our urban forest. Overall, support for private tree protection is strong. A few points to note from the survey summary: 

• More than 85% of all respondents support private tree protection for trees over 18 inches in diameter. 
• There are differences between renters (17.49% or 378 responses) and owners (75.8% or 1,638 responses) with renters more supportive of the city taking over tree maintenance and for minimum shade requirements. 
• There is overall support for a fee to help maintain street trees, which is highest at the $50-75k income bracket (75%) and is lower for the highest and lowest income brackets ($150k+ at 67.05% support and <$25k at 66.67% support).

Remember to visit the CSU Extension Yard and Garden website for more gardening tips and to prepare for next year’s season. You can also reach out to the Colorado Master Gardener’s office with any yard or gardening questions: 720.913.5270 – we’re available year-round!

Growing Garlic in Colorado

By Felicia Brower, CSU Extension – Denver Master Gardener since 2020

Photo credit: Felicia Brower

*There’s still time to get your garlic in the ground! This week’s blog post is an older post with updated photos, and it covers what you need to do now to have great garlic next year.*

As we wrap up our gardens this season, we can begin to think about all of the crops we want next year. If garlic is on your list, now is the time to act.

Garlic (Allium sativum) is easy to grow and a great crop for beginner gardeners. Even though you’ll harvest in July, you’ll need to plant before the end of October. When choosing which garlic you want to plant, know that you’ll need to purchase your bulbs from a garden center, a farmers market, a garlic farm, or a seed catalog (now is the time to place orders for garlic — they sell out quickly this time of year). Grocery store garlic is often treated with anti-growth products that will prevent you from being able to grow your own bulbs from those cloves.

If it’s your first time purchasing seed garlic, you might be surprised at all of the varieties that are available. Each variety has a distinct flavor and an average number of cloves to expect per bulb, so do your research, and choose accordingly.

Choosing Garlic Varieties

There are two distinct types of garlic to choose from: hardneck (ophioscorodon) and softneck (sativum).

Hardneck

Hardneck varieties are easy to identify because of the (you guessed it) hard neck or stem that you’ll find in the center of the bulb. While hardnecks don’t store as long as softnecks, the flavors are often described as being more intense. Hardneck garlic plants produce a scape, which looks like a curly spike with a small bulbous end. Scapes tend to show up a month or so before the plant is ready to harvest and need to be removed so that the plant can continue to send energy down to the development of the new bulb. Good news: scapes are also edible. Popular varieties of hardneck garlic include Chesnok Red, Music, and German Extra Hardy.

A scape on a hardneck variety of garlic. Photo credit: Felicia Brower

Softneck

Softneck varieties are often chosen because they tend to store longer than hardneck varieties, but they have a milder flavor. Most grocery stores carry softneck garlic, and the cloves tend to be smaller and more plentiful. Garlic braids are made with softneck varieties. Popular softneck varieties include Inchelium Red, Silverskin, and Lorz Italian.

Planting Garlic

Garlic plants don’t take up a lot of space and are known to repel rabbits and deer, so consider planting them around the edges of your vegetable and flower beds. Find a sunny spot and prepare your soil by digging a trench. If you notice you have heavy clay soil or very sandy soil, you should amend the soil with some compost prior to planting.

To prepare the garlic for planting, break apart each bulb into cloves, keeping the wrapper on each clove. Choose only the largest cloves to plant to ensure the best and biggest bulbs next summer, and use the smaller cloves for food. Plant the cloves immediately after breaking them apart from the bulb to reduce to risk of disease and excess drying.

Make a trench in the soil three times as deep as the clove. Plant each clove pointy side up four to six inches apart. Cover the cloves with soil, water well, and cover the trench with mulch, leaf litter, or grass clippings. Garlic needs water to grow and thrive, so make sure that you continue to water occasionally (about once every three weeks) throughout the winter season.

The tops of the the plants will start to come up through the winter, but don’t worry. Garlic is a hardy plant, and it should survive. Pull any weeds near the plant as it grows, as they will impact the size of the bulb.

If you plant different varieties in your garden, label each one so that you can make keep records of what grew best and which flavors you preferred for the next time you plant.

While garlic is an easy crop to grow, it is vulnerable to several types of rot. Avoid disease by planting only healthy cloves and being careful not to damage any bulbs while planting things nearby in the spring.

Harvesting Garlic

It’s time to harvest your garlic when the green tops turn brown and begin die down, which typically happens in July if you plant in October. If the soil is loose, you can pull the new bulb up by hand, but if it’s not, use a hand tool to get it out of the soil being very careful not to puncture any of the cloves. If you pull the bulb out of compacted soil, it can create wounds in the bulbs or the stem, which can quickly lead to fungal infections. When they’re removed from the soil, gently brush or rub the dirt off and let the remaining residue dry while the garlic cures. Fresh bulbs are very sensitive and bruise easily, so take care with the removal process.

Curing Garlic

If you want your garlic harvest to last, you need to cure it before you store it. After you pull the bulbs, spread them over or hang them in a warm, airy spot out of direct sun. Do not cover the bulbs with any heavy material, as that can prevent the air flow and encourage rot. If needed, use a lightweight cotton sheet. Store the bulbs at 40-60° F and cure for two to three weeks.

Cured and cleaned Romanian Red garlic. Photo credit: Felicia Brower

For a visual demonstration of how to plant garlic, watch How to Grow Garlic in Colorado – Produced by Tagawa Gardens, a partner in PlantTalk Colorado.

Colorado Gardening Calendar for October 2023

By Margerie Hicks, CSU Extension – Denver Master Gardener since 2010

October is my favorite month to enjoy the vibrant, intense colors and crisp autumn breezes of Colorado. Gardeners need to adjust their routines to ensure a healthy, beautiful garden next year by completing the maintenance tasks outlined here that apply to your garden.

Vegetable Garden

Harvesting carrots and beets photo by a-lesa on iStock

• Harvest and Preserve: Your vegetable garden may still be yielding some late-season treasures. Harvest your remaining root vegetables and squash. Store them in a cool dry place for use throughout the winter. Consider canning or freezing surplus produce or donating some to a food bank. For canning information click here. The first frost will probably occur mid-month, so don’t be caught harvesting one night in a freezing drizzle (I’m speaking from experience); observe the weather reports each day.
• Clean and Compost: Remove spent plants and weeds from your garden beds to prevent diseases and pests from overwintering. Compost healthy plant material to create nutrient-rich soil for next spring. Learn more about composting techniques here.
• Plant Cover Crops: Protect your garden’s soil during the harsh winter months by sowing cover crops like winter rye. These cover crops help prevent soil erosion, suppress weeds, and improve soil structure. When spring arrives, you can simply turn them under to add organic matter to your soil.

Trees and Shrubs

• Blow out the sprinkler system: When water freezes the pipes may crack.
• Wrap the trunks of trees that have been planted in the last one or two years:  Click here for details.
• Prune and trim: See this Colorado State Forest Service pruning guide. Do not prune spring flowering shrubs or you will be removing next year’s blooms. In the future, prune these soon after the blooms fade. 
• Irrigate: Continue to water, and plan for monthly watering all winter on days the temperature is above 40 degrees Fahrenheit.

Lawn Care

child playing in leaves photo by Scott Webb on Unsplash.com

• Rake leaves:  First form big piles so the children in your life can play in them. Then compost the leaves at home or take them, ideally in paper bags, to one of the leaf drop sites provided by the City of Denver. Click here for locations, dates, and times.
• Fertilize: Click here for details on proper lawn fertilization.
• Aerate: Unless your lawn has been aerated since spring, see the sub section of this fact sheet called “Core Cultivation or Aerating” to learn more.

Perennial Flower Beds

Planting tulip bulbs photo by LianeM on iStock

• Plant spring bulbs: Tulip, hyacinth, crocus, daffodil and other spring blooming bulbs can be planted when the weather gets cool. See this fact sheet for important considerations in selecting and planting bulbs.
• Divide and transplant: October is the ideal time to divide overgrown perennials. This process rejuvenates the plants and can also provide you with new additions to your garden. Transplant them to new areas or share them with fellow gardeners.
• Cut back and clean: Trim back faded perennial foliage and remove debris from your flower beds. Consider leaving some plants uncut, such as ornamental grasses and dried echinacea blossoms, as winter habitat and seeds for birds. These and other plants, such as Autumn Joy sedum, provide winter interest to the garden.

Annual Flower Beds

Ornamental Cabbage photo by Santi WiWatchaikul on iStock

• Plant cool season annuals: Extend the beauty of your garden by introducing cool season annuals like pansies, violas, and ornamental kale or cabbage. These hardy plants can withstand the cooler temperatures of late fall and early winter, adding vibrant color to your landscape.
• Enjoy blooms inside: Before the frost, cut any remaining blooms, such as roses, bring them in the house, and put in vases to enjoy the last summer color.

Other Tasks

• Bring in house plants from the patio before the inevitable frost. First, hose off the summer dust and any insects, then let them dry while still outside.
• Wash and store pots; clean, sharpen, and oil garden tools; store for the winter.

October is a transitional month in Colorado gardening. Use this month to prepare your garden for the winter months ahead. Remember to adapt these guidelines to your specific microclimate and garden conditions, and always consult research-based resources such as https://extension.colostate.edu/topic-areas/yard-garden/ for the most accurate advice. Happy gardening.

Planting Fall Perennials and Bulbs

By: Molly Gaines, CSU Extension-Denver Master Gardener since 2019

Our lovely Blue Mist spirea buzzed with bees. Spirea is a great choice for fall planting. Place in full sun; requires little water once established.

September is coming in hot with another streak of 90-plus degree temperatures. But our first frost could be only a month away. This makes it a great time to assess your gardens for beleaguered plantings or spaces for new ones that will add repetition, variety, color or texture next spring. Perennials, which live for many years under the right growing conditions, are an excellent choice as they are quickly established and provide a beautiful landscape around one’s home. Fall, with its cooling temperatures yet warm soil, is an ideal time in Denver to plant most perennials, including bulbs.

Last week, my husband and I did some assessing of our space for new perennial plantings. This followed an unfortunate incident in our front yard. Per our request, the owner of an unoccupied house next door removed massive patches of 7-foot tall thistles and copious bindweed encroaching on our lawn and garden. In the process, the workers mistook our 10-year-old blue mist spirea for a weed.

At first I was highly annoyed this gorgeous perennial woody shrub had been removed, leaving a gaping hole and hundreds of bees homeless. But after a few minutes the shock wore off and I got excited about planting something new. This weekend, we’ll make a trip to our favorite garden store to walk the aisles, selecting whatever perennial promises to bring new life and color to our yard.

I’ve also been wanting to add early spring pops of color to our beds. For this I’ll turn to tulips, hyacinth and maybe some daffodils. I’m also looking at more groundcover, perhaps light pink dianthus, which also loves to be planted in the fall. Our garden also needs new ornamental grasses, ideal for our dry climate, but those require more time to get established before winter. If I want to plant those, I need to do it soon as they should be in the ground at least a month before the first frost.

Wisteria is a perennial that quickly establishes itself as a prolific climber with beautiful purple flowers.

There are a number of perennial plants, flowers, trees and veggies that are excellent choices to for fall planting. Water them frequently so their root systems adequately establish before the ground freezes and they go dormant for the winter. Don’t forget to winter water during dry spells. Find tips here.

Here are a few to consider:

Bulbs

It’s delightful to see the first crocuses blooming in March, a tell-tale sign that spring is coming. Additional early bloomers to consider include snowdrops, species tulips, dwarf iris and Siberian squill. To keep the color going through spring, think about grape hyacinths (oh that intoxicating scent!), tulips or daffodils. For early summer blooms, alliums, bearded iris and Dutch iris are also good considerations. For great information about bulb selection and planting, visit this CMG blog post or this fact sheet from PlantTalk. One tip to remember: plant each bulb 2-3 times as deep as the length of the bulb itself.

Crocus in bloom on March 23 in Denver.

Perennials

For a terrific overview of everything you’d want to know about perennials, from designing a space, to selecting plants, to getting them in the ground, check out this Colorado State University (CSU) fact sheet.

When it comes to choosing perennial plants for fall planting, I find garden centers naturally guide the selection process based upon what they are selling. Here’s a comprehensive list from CSU of perennial options that thrive in our higher elevations and are suitable for sunny, partial sun and shady locations.

If you’re interested in newcomers to our Denver gardens and they are available, consider recommendations from Colorado State University researchers. Last year, they released a list of the top 8 best new perennials to grow in in our Rocky Mountain climate. These include Firefly Sunshine yarrow, Alchemy Silver brunnera, Euphoria Ruby Joe-Pye weed, Crazy Blue Russian sage, Prima Angelina sedum and Moody Blues veronica (mauve improved). A note on roses: while there are roses on this list, according to CSU, they are better-suited to spring planting.

After hot summer days, endless weeding tasks and the constant watering our Denver gardens demand, the fall season calls us to relax into the landscapes we’ve created. But a final push of perennial planting will be appreciated next spring as new life emerges, along with the promise a new gardening season holds.

Colorado Gardening Calendar for September 2023

By Valerie Podmore, CSU Extension-Denver Master Gardener since 2020

Winecups reaching for water. Photo by Valerie Podmore

When I went on my (mostly) daily morning walk (I’m writing this in the 3^rd week of August by the way), the temperature was a lovely mid 70’s and my walking buddy said, “this is a really nice morning, almost like fall.” As we’ve had so many hot, hot July and August days, the thought of experiencing cooler ones is quite appealing! I’m sure our plants will enjoy that as well (not the walking part of course haha). Let’s look at our gardening to-dos for this month.

Vegetable Garden

Ok I admit, my first attempts at veggie gardening are not going great, mostly because I’ve not watered properly, I think. It could also be the location has much more shade than initially imagined. Remember that right plant, right place mantra? I didn’t! In any case, here are some tasks to perform this month for those of you who actually have real vegetables growing.

• Continue to harvest any ripe summer vegetables and clear out fallen leaves, weeds and other disease-causing debris.
• Plant cool weather vegetables now as they mature quickly and love less heat. These include lettuce, kale, arugula, Swiss chard, and spinach. Here’s a timely post on how to extend our growing season.
• Don’t forget to continue watering because we all know that Colorado can throw crazy weather at us…and it follows then to prepare for cold weather snaps too. There’s nothing worse than working so hard to grow something only to have it destroyed by Mother Nature. 

Trees and Shrubs

• Oh that watering thing again. It’s like some sort of Tamagotchi game (showing my age!) to make us desperately try to keep our plants alive! Keep an eye on the weather and water deeply when precipitation has been scarce. This information sheet has EVERYTHING you want to know about water.
• While we can prune, if necessary, try to avoid it during this month. Make note of branches that need attention and save the tasks for late winter or early spring.
• We may not realize it, but September’s cooler temperatures make it a good time to plant trees and shrubs as it gives enough time for the plant to acclimate in the warmer soil and prepare for the winter months. Here’s a great article on this very idea.

Lawn Care 

• This is a great month to revive our lawns by aerating and fertilizing or overseeding bare spots.
• As mentioned above, watering is still important to keep our lawns healthy so let’s continue caring for our lawns as fall is not the time to stop the good lawn care practices we’ve undertaken throughout the year.
• Tired of dealing with lawn? Now’s the time to start to plan a turf conversion. This page offers practical tips.

‘Autumn Joy’ sedum’s dusty pink blooms pop in September and last till frost. Photo by Linda McDonnell

Perennial Flower Beds 

• This is a perfect time to start cleaning up our plants as they begin to go dormant, by clearing away dead and mushy leaves, fruits or weeds which can cause disease.
• This quick read has good advice on clearing up the garden in the fall and pollinator-friendly clean up tips can be found here.
• Divide early blooming perennials such as iris, lily, hostas, bleeding hearts, and other bulb or tuberous species to keep them from crowding each other too much.
• For anyone who has a spare hour and some, and REALLY wants to nerd out on fall plant advice, take a look at this awesome video!

Annual Flower Beds

Because I’m lazy, I prefer perennial plants but of course we can’t minimize the impact that annuals have in the garden. The colors and variety are just so great!

• Make note of those annuals that you will want to replace next year.
• Get your pots of Chrysanthemums or pansies busted out to provide fall color, as these plants prefer cooler weather and add that color we sometimes need to combat that seasonal affective disorder that we have (well I’m speaking for myself here!).

As always, visit the CSU Extension Yard and Garden website for more gardening tips.

Rinse and Repeat: Extend the Vegetable Season with Canny August Planting

By Terry Deem-Reilly, CSU Extension – Denver County Master Gardener since 2003

Cultivating a vegetable garden this spring was certainly a challenge – we had late snow, followed by almost constant rain and, finally, some killer hailstorms. Seeds and seedlings were drowned or drifted into neighboring patches of soil and planting was delayed due to soggy soil conditions. Then cool temperatures and heavy rains required us to protect heat-lovers like tomatoes and peppers and stunted their growth. 

Late June hail decimated some Denver gardens. Photo: Molly Gaines

As I write this, we’re experiencing some typical July heat while forecasters are predicting a temperature dip that will lower temperatures to a more comfortable level. We can look forward to an abundant second harvest in September and October if we take advantage of better planting conditions this month.

WHEN AND WHAT SHOULD I PLANT?

Before answering the questions of when and what to plant, determine this year’s anticipated first frost date. Do this by counting backward from the number of days or weeks to maturity for each plant species. This will give you the date on which seeds must be planted. 

Find the first 2023 frost date for your city on the website of the Old Farmer’s Almanac. This resource estimates Denver’s first frost to occur on or about October 6^th , however this is only an approximation – keep up with local weather predictions as summer turns into fall. And remember that we can be flexible, thanks to plant protectors and moveable containers! 

Next, decide what to plant. The Denver Urban Gardens site features a guide to vegetable planting for commonly grown vegetables. It shows the recommended number of weeks (not days) to plant before the first frost. The column headed “fall planting” has the information to reference for the late gardening season. Note that we’re inside of or past the optimal seeding date for a number of these plants. Given this, consider using vegetable starts instead of seeds, and/or grow in containers that are easy to move or cover as the first frost approaches.

If seeing drop-dead dates for planting better suits your style, check out the ‘Colorado Vegetable Planting Calendar’ on the Asia Farming website.

Plant radishes now for a fall crop.

Before heading to the nursery –- and certainly before starting to plant –- take a look at Pueblo County Extension’s publication, “Late Summer and Fall Vegetable Garden Planting” for advice on plant selection and improving the tilth of soil that’s been used to grow the summer crop. 

If you like perennial herbs – decorative or culinary –- look for them in pots when you’re out and about looking for vegetable starts and seeds. Herbs like winter savory, lavender, and thyme will overwinter and, in some cases, remain green for cold-weather interest. Mulch well and water regularly until the soil freezes in late November to promote good root growth for a fast start in the spring. Perennial herbs in small containers  can be brought inside during the winter and returned outdoors to perk up the garden as soon as nighttime temperatures warm to a safe level in spring. This website lists some perennials that survive Zone 4 and 5 winters and popular annual herbs for fall planting.

It’s not quite time to plant garlic, but if it’s on your fall schedule, the sheer number of available cultivars and flavors requires researching possibilities and ordering bulbs NOW. Here’s a good article about growing this crop in Colorado, featuring some well-performing varieties. Local nurseries are or will soon be stocking garlic bulbs but consult some mail-order sources for the more exotic types. And for everything essential to know about growing garlic in our climate, check out the Master Gardeners’ September 2020 blog post “‘Growing Garlic in Colorado.”’

PLANNING FOR DISASTER

Inevitably an unexpected run of bad weather will occur in September or October: a hard freeze, rains that drown seeds and seedlings, even a heavy wet snow that brings the growing season to a screeching halt by snapping plant stems in two and withering tender foliage. We can minimize this damage by using a few effective tools:

• Row covers and frost blankets (sheets from the linen closet will work in a pinch)
• Anti-freeze bags (these come in many different sizes and are great for bushy plants)
• Cold frames (require advance construction but are handy year-round)
• Morning watering when frost is expected that night (hydrated plants are more resistant to frost damage)

Good luck with your late-season veggies! As always, please contact the Denver County Extension with your gardening questions. 

Low-Water Vegetable Gardening in Colorado

By Felicia Brower, CSU Extension – Denver Master Gardener since 2020

Water and vegetables go hand-in-hand. The more water you give to your growing vegetables, the bigger and better tasting the harvests tend to be. As water restrictions become common and conserving water becomes more important than ever, it’s going to be crucial for gardeners in Colorado to figure out how to resourcefully use water if they want to keep growing fresh vegetables.

There are a few key ways to cut back on water in the garden. Simple things like choosing vegetables that can survive (and even thrive) using less water, maximizing the water that you do use, and preventing water loss are all ways to keep your garden looking great without relying on excess water.

Chives are always the first thing to pop up in spring without any supplemental water. Photo by Felicia Brower

When it comes to choosing what to grow in your garden, it’s important to remember that different vegetables require different amounts of water. Vine crops need less water (and actually tend to be overwatered in the home garden), while beans and sweet corn typically need more water than other types of vegetables. Many perennial herbs don’t require a lot (if any) supplemental watering to do well. My parsley, chives, sage, thyme, and lemon balm are the first things to show up every year in my garden without any extra water to help them grow.

Not only do vegetables have different water needs, but some also need more water during certain parts of their life cycles. For example, peas need more water during their pod filling period while tomatoes need more water during flowering and fruiting. 

It’s also important to choose regionally-adapted vegetables. Vegetables that are selectively bred to excel in areas where drought is common are more likely to have fewer issues when they’re watered less in the home landscape. Search online for Colorado seed companies and choose vegetable varieties that are drought tolerant. While beans can often be huge water users in the garden, varieties like Zuni Gold, Paiute Gold tepary, and Sonoran White tepary are drought-tolerant and grow well without needing huge amounts of water. In fact, during some of my drier years, they stayed greener and kept producing while their neighbors wilted and struggled. 

Zuni Gold beans, a southwest Pueblo variety, are highly adaptable and drought tolerant, making them a favorite in my home garden.
Photo by Felicia Brower.

One of the best ways to conserve water is to maximize water efficiency. If possible, install in-ground drip irrigation or use cost-effective soaker hoses so that your water reaches the roots of the plants instead of being wasted on foliage or in spots without anything growing. Water at soil level near the roots in the morning, avoiding the heat of the day, to reduce the amount of water lost to evaporation and to avoid issues like powdery mildew on the leaves of your plants. 

Here are a few additional ways to grow a low-water vegetable garden: 

• Different soil types have different water needs, so water according to your specific soil type. Loamy soil needs deep, infrequent watering instead of regular, light daily watering while sandy soils need more frequent, less deep watering because they lose water faster than clay soils. 
• If you use overhead watering, don’t water your plants on very windy days. The wind will blow your water away and prevent it from reaching the roots. 
• Before you do any watering, test your soil’s moisture level. The surface of the soil might be dry but the roots might not be.
• Your garden layout can also impact how much and often you have to water your garden. Narrow rows need more water, so grow your veggies in beds, grids, or wide rows. 
• As with any plants in your home landscape, plant vegetables with similar water needs together. If you have a mix of drought tolerant plants and high-water plants, make sure they’re kept separate so you don’t overwater or underwater, both of which cause stress and can impact the quality of your harvest.
• Use mulch (green or otherwise) to keep moisture in the soil. You won’t have to water as much if you grow intensely (close together) or use another organic mulch to slow down evaporation. 
• Grow during Colorado’s shoulder seasons to take advantage of moisture from snow and spring rains and cooler temperatures, so there’s less water loss due to heat.
• Before you plant anything, take time to amend and prep your soil. Healthy soil retains water and is full of nutrients that prevent you from overwatering to try and make your plants stronger. 

As water conservation becomes more important in the west, it’s crucial to find ways to use less, especially for things like growing food. Follow CSU’s Colorado Vegetable Guide and the “Water Conservation in the Vegetable Garden” GardenNotes chapter for advice on best low-water vegetable gardening practices. 

Planning a Garden for Thrills Spring to Fall

By Terry Deem-Reilly, CSU Extension – Denver County Master Gardener since 2003

One of the most satisfying aspects of gardening is seeing dormant sticks, clumps, and bulbs that were placed so hopefully in the soil leaf, blossom, and fruit. At the same time, one of the most daunting aspects of gardening is ensuring that all of that leafing, blossoming, and fruiting doesn’t occur all at one time. A garden that ceases to bloom after the last tulip has disappeared or browns up from the fall equinox until the following spring won’t satisfy the senses nearly as much as one that displays continuous interest. Moreover, landscapes which produce pollen and nectar throughout the season provide important nourishment for pollinators.

Hellebores kick off the season. Pixabay.com

Other posts in this blog have stressed the necessity of matching plants to sites, soil, and sun exposure that will allow them to flourish. Horticultural considerations don’t disappear when the goal is season-long color and interest; selecting plants that like the same conditions and grouping them into the areas where they’re most likely to flourish are indispensable to having the three-season garden of your dreams.

The detailed first steps to success with any perennial garden can’t be adequately covered here but are well-explained in the Extension fact sheet Perennial Gardening. Remember the conditions in your site when reviewing plant lists.

Next, consider whether you’d like to include non-native or xeric/native trees, perennials, and shrubs; this decision will determine the amount of time and attention (not to mention water) you’re going to devote to a three-season garden. Xeric plants and Western natives won’t need much maintenance after the first season or two, but a lush English-style bed of roses, delphiniums, and pinks demands careful soil amendment and regular irrigation, mulching, and fertilization. Decide what look you’re after and what it will take to achieve it.

Mid-summer morning & the garden’s in full bloom. Photo: Linda McDonnell

To make plant selection a little easier, here are suggestions from plant lists showing seasonal bloom by non-xeric and xeric/native varieties, with links to the complete lists for easy reference.

Nonxeric or Non-Native Perennials

• Spring: early blooming bulbs, primrose, candytuft, viola, creeping phlox, hellebore, peony, geranium
• Summer: garden phlox, dianthus, lily, verbascum, hosta, campanula
• Fall: aster, chrysanthemum, Japanese anemone, lobelia

For the complete list, see the Plan Your Garden with our Perennial Flowering Plants by Season Guide. Some of the plants shown above also appear in 25 Perennial Flowers That Bloom From Spring To Fall. Timberline Landscaping in Colorado Springs has published a bloom calendar of perennials that do well on the Front Range.

Xeric and/or Native Perennials

• Spring: early blooming bulbs, columbine, amsonia, windflower, pasque flower
• Summer: chocolate flower, poppy mallow, asclepias, eriogonum, penstemon, oenothera
• Fall: helianthus, asclepias, winecups, hyssop, agastache

These plants, and many others, can be found in these Extension fact sheets: Native Herbaceous Perennials for Colorado Landscapes and Xeriscaping: Perennials and Annual Flowers. These resources also indicate water needs, light requirements, and plant heights and descriptions.

Want to see more native plants? CSU’s Low-Water Native Plants for Colorado Gardens: Front Range & Foothills includes not only common and botanical names; height; color, size, water and sun requirements; and wildlife value, but also design plans and photos of great local native gardens. Mountain residents will find the Extension fact sheet  Flowers for Mountain Communities useful for plant selection and advice on cultivation.

Shrubs and Trees

Hawthorn tree in fall. Pixabay.com

Our guide wouldn’t be complete without recommendations for suitable trees and shrubs to supplement your perennial display. Many plants in these categories offer blossoms, fruits, and/or color that add interest throughout the season; a number of them offer all three!

Here are examples of shrubs that add color and interest through the seasons:

• Serviceberry
• Fremont mahonia
• American plum
• Buffaloberry
• Western sand cherry

For a complete list, consult the Extension fact sheet Native Shrubs for Colorado Landscapes. Again, you’ll see botanical and common names, size, and sun, moisture, and sun requirements for each shrub.

Some trees that add interest include:

• European mountain ash
• Pine
• Colorado blue spruce
• Aspen (Foothills and submontane areas only!)
• Maple

See the fact sheet Native Trees for Colorado Landscapes and the CSU publication Recommended Trees for Colorado Front Range Communities for more details. Mountain gardeners should consult the fact sheet Trees and Shrubs for Mountain Areas for suggestions.

Finally, don’t discount the value of roses when planning for season-long color. Even with the plague of the Japanese beetle, roses (especially hip-bearing and species roses) dependably add color through the growing season. The Denver Rose Society publishes a list of the best roses for our climate: Recommended Roses for Colorado.

If problems arise, always, ALWAYS rely on research-based information to answer your questions;  Denver Extension stands ready to help!

Fall Blooming Saffron Crocus

Lori Williams, CSU Extension – Denver Master Gardener since 2016

Saffron Crocus flower and grass-like leaves. Photo: Lori Williams

Saffron is one of the most exotic and expensive spices in the world, prized for its complex, sweet and earthy flavor. This highly desirable seasoning comes from the red female pollen receptors or stamens of the fall blooming saffron crocus (Crocus sativus). While the plant looks like the familiar spring blooming crocus, only saffron crocus produces this coveted culinary ingredient.

Lucky for Colorado front range gardeners, saffron crocus is hardy in our zone 5 climate and once established, is drought tolerant. I added it to my garden three years ago and am really enjoying it.

Let’s take a look at the plant’s history and tips for growing and harvesting.

Saffron Through the Ages

For centuries, saffron has been used in a wide variety of ways – as a richly scented perfume ingredient, a vibrant fabric and ink dye, an aide in organ functioning, and to beat the blues – to name just a few. Reportedly, Cleopatra soaked in saffron-infused baths as she liked the luminous glow it gave her skin. Today, saffron’ s most notable use is as a flavorful seasoning in sweet and savory dishes.

Planting Tips and Growth Cycle

Saffron crocus plants develop from corms (a squat shaped bulb). Since the Denver area is on the cold edge of the plant’s hardiness range (zone 5),  plants will benefit from the sunniest location possible.

Plant six weeks before the expected first frost. Bury corms in well-draining soil, 2-3 inches deep, 3-4 inches apart with pointy end up and ‘hairy’ end down. For successful flowering, nighttime soil temperatures should be as low as 40 degrees. Corms spoil quickly so plant soon after purchasing.

Thin, grass-like leaves sprout in 4-10 weeks, followed shortly by 2-4 purplish cup-shaped blooms which last up to a month.

The foliage remains green for months while underground the ‘mother’ corm multiplies or produces ‘daughters.’

Leaves yellow and die in spring; plants will be dormant in summer. Divide bulbs every 3-5 years during the late summer dormant period.

The saffron crocus lifecycle. ( University of Vermont)

Harvesting Saffron

Timing and TLC are critical to capturing maximum flavor. This is where the labor cost of commercially grown saffron adds up. Plants are low-yield and picked by hand – producing just three stigmas per flower. It takes 4600 flowers to produce one ounce of saffron. It’s no wonder that today .03 ounce of the spice costs $24!

Some growers believe the most robust flavor comes from the morning harvest of the season’s first blooms. Imagine watchful workers jumping into action on that first morning, hand plucking dark red threads from each flower.

Saffron threads on leaf. Photo: Lori Williams

Here are harvesting tips for the home gardener:

• Allow the plant to mature for an entire life cycle before collecting the stigmas. My initial year’s growth was small and floppy, with underdeveloped stigma, so I just enjoyed the prettiness.
• Microclimates impact plant growth and saffron production. This year, my esteemed master gardener friend who gardens to the south of me completed harvesting by mid-October, mine flowered about two weeks later.
• Remove the long, crimson red stigma by hand when flowers are in bloom. Last year I harvested a few days post-bloom which resulted in orange-stained fingers and strands that went *POOF* into dust the moment they were touched. A good, but hard lesson to learn.

Saffron is amazing fresh; however, it’s more commonly used dry. To preserve it, lay the threads on paper towels and protect from light to maintain flavor. When dry, wrap threads in foil and place in an air-tight container. Ideal storage temperature is 77 degrees.

Resources and References

Saffron crocus is getting easier to find at local garden centers and there are many reputable growers online and via catalogues. This Nebraska Extension article includes a helpful list.

This video from a Tasmanian saffron farm is fun to watch.

America’s Test Kitchen offers some mouth-watering sweet and savory saffron recipes here.

The University of Vermont is home to the North American Center for Saffron Research and Development.

Saffron crocus is a lovely addition to the fall garden as well as your spice rack. I hope you’ll try growing it!