Colorado Gardening Calendar for April 2024

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

Last week’s snow covering forsythia starting to bloom. Photo: Molly Gaines

Signs of spring are everywhere in Denver. Daffodils, crocus and other spring flowers in full bloom one day; covered in ice and snow the next. Oh, to be a gardener at 5,280 feet!

While it’s too early to spend a lot of time planting, it’s a perfect time to prepare your soil, garden beds, tools, pots and lawn for the 2024 growing season. Below are a few gardening activities to consider before Mother’s Day, May 12 (around the safe zone from hard frosts) for planting most plants, flowers and vegetables.

Crocus are always a welcome first sign of springtime. Photo: Molly Gaines

As you plan your garden, it’s worth noting that some of the Denver metro is in a new gardening zone. Last November, the USDA announced updates to its “Plant Hardiness Zone Map,” updating this go-to tool for gardeners for the first time since 2012. The new map, which can be found here, places parts of Denver in Zone 6a rather than 5b. Zone numbers reflect the average extreme minimum temperatures and help determine what plants will thrive in each zone.  Higher numbers equal incrementally warmer low temperatures. For background about how to use this map as a planting guide, visit this helpful article from the National Gardening Association’s learning library.    

New USDA Plant Hariness Zone Map now places parts of Denver in Zone 6A. Credit: USDA

Vegetable Garden

• Clear remaining debris. Pull emerging weeds.
• When the soil is dry, add a fresh 2-3-inch layer of compost to your beds. This supports soil health and plant vigor. Gently work compost into the top layer of your existing soil with your hands, a trowel or a cultivator. Let rest a few weeks before planting.
• Plant frost-tolerant spring plantings, such as peas, spinach, arugula, radishes, Swiss chard, etc.
• Start indoor seeds for warm-weather vegetables such as tomatoes, peppers, squash, melons, etc.
• Reference this Vegetable Planting Guide to plan what you will plant when.

Trees & Shrubs

• The snowpack is solid Colorado-wide this year, well above 100 percent. This includes Denver. That said, if this month is dry, be sure to water your trees and shrubs.
• Early this month, prune deciduous trees, conifers and summer-blooming shrubs.
• Later in April into mid-May, prune rose bushes. For details on exactly how, why and when to do this, visit here.  This is weather dependent so watch for low temperatures and delay if a cold snap is predicted.
• Remove broken branches from trees and clear dead leaves and decayed fruit from the base.
• If you’re looking to plant a new tree, consider the Park People’s annual fruit and yard tree sale that begins April 20. Trees range from $50 to $80, and sales support the Denver Digs program. More details can be found here.  

Lawn Care

• Prep your mower, sharpening the blade as necessary and conducting other maintenance. Lawn mower blades should be sharpened at least once per season.
• If you use a pre-emergent weed product, apply in early April. For more details about how to use, visit here.
• Fertilize as desired, reading labels for proper application. Keep in mind that fall is the most important time for lawn fertilization. Applying only in the spring can mean excessive top growth and shallow root systems.

Perennial Beds

• Cut back perennial plants if this wasn’t done last fall, leaving 3 inches of the plant above the soil.
• Similar to your vegetable garden, the soil in these beds will also benefit greatly from compost, with the exception of native plants which generally prefer unamended soil.
• Pull emerging weeds now. Stay on top of them from the start.
• Divide overgrown perennials such as chives, sedum, grasses, phlox, daisies, hosta, etc. This will lead to healthier plants and better growth.

Other April Gardening Thoughts

• Assess garden supplies. Purchase or plan to borrow anything needed. Sterilize and sharpen garden tools.
• Empty any pots or containers still holding last year’s dead plantings. Clean and disinfect them to prevent disease in new plantings.

These pots need to be cleared of last year’s plantings, disinfected and filled with new soil for plantings. Photo: Molly Gaines

• Denver Water recommends waiting to turn on your irrigation until after the last freeze, typically in early May. Hand water until then.
• Sow wildflower and pollinator seed mixes.
• Prepare for frost, hail and other bad weather. Have sheets of plastic, old bedsheets and five-gallon buckets in easy reach for late-season snow or spring and summer hail. Remember the hailstorm that hit Denver late June last season?

Sad peas in a bed covered with hail. June 29, 2023. Photo: Molly Gaines

Springtime in Denver is special. I love watching new life slowly unveil itself. It’s a time full of promise, new beginnings and high anticipation of the color, flavor and textures around the corner. The more prepared you are in April, the more enjoyable your summer gardening season will be.

As always, if you have questions about plants, planting and any other gardening and yard related topics, visit the CSU Extension Yard and Garden website for tips.

Colorado Gardening Calendar for February 2024

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

Blue fescue grass poking through snow at Denver Botanic Gardens. Photo: Margerie Hicks

February is one of the best months to enjoy the interesting patterns, textures, and shapes that dried grasses and perennials form in contrast to the snow. It is also a time to read or otherwise educate yourself about gardening trends and ideas. And finally, it is a time to complete the few but important tasks needed in February to prepare for the coming growing season.

Winter Interest

Autumn joy sedum keeps its color and form. Photo: Margerie Hicks

If you refrained in the fall from cutting down ornamental grasses, perennials with balls of seeds like echinacea, or plants that keep their color and form, you now have interesting winter patterns and shapes to enjoy. You have also helped provide shelter and food for wildlife, such as birds and insects.

If you don’t already have any sedum Angelina, make a note to plant some in the spring to enjoy next winter. It is a ground cover that is light green in the spring, yellow in the summer, and orange with green accents in the winter. It provides a wonderful splash of color in the winterscape.

Sedum Angelina adds multi-season beauty. Photos: David J. Stang, CC BY-SA 4.0 via Wikimedia Commons

Gardening Edification

• Expo: The annual Colorado Home and Garden Show runs from February 24^thto March 3^rd. Master Gardeners will be on hand to answer gardening questions at the large CSU Extension display. Be sure to stop by and say hi.
• Books: You may have some gardening-related books waiting to read on a cold winter night, but in case you want suggestions check out our earlier post,  Winter Reading for Gardeners.
• Websites: CSU Extension’s website offers research-based fact sheets and videos on a wide range of gardening topics. Additionally, the internet is filled with gardening information and pictures. The most reliable sources have an “.edu” extension on the address, indicating an affiliation with university horticulture/agriculture research.
• Gardening classes:  Local garden shops and the Denver Botanic Gardens offer classes on many topics that may pique your interest. You can also find a wide array of webinars offered by CSU Extension here.
• Take our reader survey:  We’d love your feedback and ideas for future posts. Find the survey here. Survey closes February 18^th.

February Tasks

Deep watering tool. Photo: Margerie Hicks

There are a few tasks that should be done and many that could be done this month. A good overview can be found in this Late Winter Garden and Lawn Care fact sheet. Key tips include:

• Water:  All trees, shrubs, and perennials will benefit from regular winter watering, especially those that are less than two years old. Water once a month on days when the temperature is 40 degrees or warmer with no snow cover. Click here for a fall and winter watering fact sheet that will make your efforts most effective.
• Mulch:  Woody plants benefit from mulch to preserve soil moisture. Rock or gravel mulch is useful in retaining heat. Apply as needed.
• Prune:  This is a good time to prune broken and unwanted branches from trees and shrubs, especially fruit trees.

Enjoy your gardening leisure in February. May will be here soon enough.

Speaking of May don’t forget to mark your calendars for our amazing plant sale!

Colorado Gardening Calendar for January 2024

Early January at the Denver Botanic Gardens Photo: Linda McDonnell

By Linda McDonnell, CSU Extension – Denver Master Gardener since 2013

It may be tempting to kick back and think there is nothing much to do in the garden this month. And while it is not the busiest time, taking a few steps when needed will set plants, trees, and lawns up for future success.

Winter Watering – January’s Most Important Task

It’s important to water trees, shrubs, perennials, and lawns during extended dry periods of 2-4 weeks. Supplemental water provides root systems with moisture that is critical to long-term plant health. It is especially crucial for new plants (1 year old or less) with smaller, less developed roots. Without this added moisture, plants may exhibit stunted growth, be more susceptible to disease, or die. Often decline is not noticeable till next summer when the root system can’t support the plant’s vigorous growth.

Water early in the day when temperatures are above forty degrees. Give plants a good soak – 8 to 12″ deep and out to the drip line of trees. Find more information on winter watering here.

Branches of  ‘Carol Mackie’ Daphne will easily split under heavy snow. Photo: Linda McDonnell

Trees and Shrubs

Heavy snow can crush or bend the limbs of trees and shrubs. Remove it by lifting branches lightly from the bottom with a broom to avoid breaking limbs. The branches will spring back as if to say thanks.

Prune any storm-damaged limbs as needed to prevent further breakage. Find additional post-storm tips here.

Perennials

Watch for signs of heaving such as cracked soil and raised crowns. This can happen around newly planted perennials when temperatures fluctuate widely. Heaving can expose and damage roots and kill plants. If heaving is present, check moisture, add soil or compost around the plant, and top with mulch.

Speaking of mulch – spread more where needed; it will help moderate temperature extremes.

Remove any diseased foliage that’s lingering in your beds to reduce the chance of infesting next season’s growth. Discard the foliage in the city’s green compost bin or trash. Home compost systems don’t get “hot” enough to destroy pathogens.

Plan Ahead

Should you keep or toss old seed packets? Learn how to tell here.

Scour online and print catalogs to find tried-and-true plant varieties along with new, buzz-worthy introductions.

The CSU Soil Testing Lab opens on January 21^st. If the ground is workable, consider beating the spring rush and sending a sample for analysis this winter. Find directions for digging the sample, using the results and costs here.

Check out the line-up of CSU’s no-cost webinars. There are lots of topics to choose from including turf alternatives, CSU test garden results, and water-saving tips. Find the full spring schedule and recordings of past webinars here.

Explore CSU’s resources for research-based gardening information that will make this year’s garden the best one yet.

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. 

Colorado Garden Calendar – December 2022

Photo: Jodi Torpey

By Linda McDonnell, CSU Extension – Denver Master Gardener since 2013

Gardening slows down in December but doesn’t stop completely. There’s still time to finish some chores from our November list, so be sure to revisit it. For the next few months, prioritize winter watering during dry spells to ensure healthy plants next year.

December’s also a great time to enjoy indoor plants, appreciate nature’s seasonal beauty, and start thinking about next year’s garden.

Here’s a run-down of tasks and activities for December.

Trees, Shrubs, and Perennials

• Winter watering is essential to long-term plant health – make it a point to water during four-week dry stretches. To ensure proper absorption, water early in the day when temperatures are above forty degrees. This post offers excellent advice on when, why, and how much to water – and photos of the impact of too little moisture.
• To help with moisture retention, replenish mulch in areas that have gotten thin.
• Shake snow from bent tree limbs and branches to avoid breakage and lightly prune any broken limbs to avoid further damage.

Compost

• Continue adding green and brown materials to your compost bin. Since decomposition is slower in cold temperatures, break your materials into smaller pieces to speed up the process. The University of New Hampshire offers more winter composting tips here.

Thanksgiving cactus approaching its fourth decade & going strong. Photo: Linda McDonnell

Houseplants

• 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 popular advice to mist with a spray bottle – to make an impact 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 regularly for pests such as mealy bugs and spider mites. If present, treat and quarantine the infected plant. Find remedies here.
• ‘Tis the season for holiday plants and live Christmas trees. Here are some helpful links to keep them 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.

Celebrate, Inspire, and Explore

• The winter solstice arrives on December 21^st. In the Northern Hemisphere, it marks the day when the sun is at its lowest height at noon as well as the shortest day of the year. Starting the next day, we’ll gain about two minutes of daylight daily till June 21^st. Yippee!
• Share your enthusiasm for gardening with a child – find a few activities here or wander the library aisles to find an inspiring book on plants or nature.
• Check out 2023 seed introductions from your favorite growers. It’s time to start scheming and dreaming about next year’s garden.

As always, CSU is available to help with gardening advice at the CSU Extension Yard and Garden website. We hope you’ll visit often.

We’ll be back in two weeks with our last post of the year. Until then, enjoy all the season brings.

Looking Forward: Planning Your 2023 Vegetable Garden for a Hotter, Drier Denver

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

I grow vegetables primarily for the vibrant, incredible flavor they almost always guarantee. So, you can imagine my disappointment when I picked my first homegrown cucumber of the 2022 season, and it tasted awful — bitter beyond redemption. 

My sad 2022 cucumbers. This one is a bit misshapen, too. Photo by Molly Gaines

When assessing what went wrong, I first blamed our hot summer. But after some self-reflection, I realized that as an experienced gardener, I should’ve been more thoughtful about what I planted and how I tended to it. As a climate pattern of hotter summer days with less moisture continues in Denver, we all need to plan for climate-resilient gardens. 

The CO Climate Trend

Colorado’s climate is trending hotter and drier. According to the National Oceanic and Atmospheric Administration, over the past decade Colorado’s annual temperature has warmed 1.1 degrees and annual precipitation has decreased by 0.22 inches. 

In September, a record was set in Denver for the most 90-degree days ever recorded. So far in 2022, Denver has experienced 66 days of 90-degree temperatures — the 3rd most in history and the 8th consecutive year above the average. 

These trends mean gardeners must plan more wisely and stay attuned to the weather, adjusting our plants’ growing conditions and nurturing them appropriately.

My Cuke Mistakes

I hastily purchased my cucumber seedlings (mistake #1) in late June after two rounds of plants withered. I planted the two new seedlings in an elevated bed with lots of other herbs and flowers. Knowing I’d packed a lot into my small garden bed, I frequently fertilized the seedlings, even as temps climbed (mistake #2). By August, I was struggling to keep them adequately watered. Cucumbers require a ton of water, especially in elevated beds, so they were occasionally stressed during the 90+ degree days (mistake #3).

While we could write a whole series of blog posts about climate-resilient gardening, we’ll use my bitter cucumber story as a top-level example of how to better plan and care for our gardens in Denver’s hotter, drier climate. 

Plan Wisely

I didn’t carefully choose the cucumbers I planted, instead grabbing what was available at my local nursery. 

If you’re growing seedlings at home or sowing directly, it’s easier to choose the best option as seed companies provide extensive background on each variety. For example, ‘Little Leaf’ cucumber would have been perfect for my elevated bed – smaller in size and producing “ fruit under stress and without pollinators, guaranteeing high yields.”

Peppers love the heat and are well-suited for our climate. Photo by Molly Gaines

Shopping for seedlings from one of the major area plant sales, such as the Denver Master Gardeners annual spring sale, is another great way to find the right plants. Varieties grown and sold are carefully selected for our region, and sale staff are equipped to answer questions.

If you experience success with a particular plant, save those seeds for next year. For guidance on seed saving, check out this excellent resource from Colorado State University.

Planting fall crops in August is challenging when temperatures still hover above 90 degrees. Consider fall vegetables that mature quickly. Radishes and greens are good candidates. 

These radishes, with approximately 25 days to maturity, are ideal for fall planting. Photo by Molly Gaines

Don’t Over Fertilize 

Excessive heat slows production. If your plants aren’t producing as they should, don’t assume they need fertilizer. This is what I did to my cucumber plants. I continued to apply fertilizer during the summer heat, which led to lots of green and hundreds of blooms, but minimal fruit. For a guide to applying fertilizer to your vegetables, check out this guide from the University of Minnesota Extension. 

Water Consistently

The direct sun and constant heat can make plants stressed. Don’t add to their stress with hit-or-miss watering. Help make your garden climate resilient with reliable, consistent drip irrigation. If you’re not able to irrigate your plants in this way, hand water in the mornings. Give your plants a deep, thorough soak at the roots. Here is a good resource for watering in the persistent heat.

Colorado gardeners are used to a challenging climate. Proper planning will allow for the most successful, climate-resilient vegetable garden possible. 

For an excellent resource about climate resilient gardening, click here. 

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Watch for future ‘Looking Forward’ posts where we’ll spotlight Master Gardeners who are applying what they’ve learned to expand, rethink, or improve gardens. 

Colorado Gardening Calendar for SEPTEMBER 2022

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

Summer’s not done yet! by Valerie Podmore

Let’s not get downhearted at the impending end of growing season! September is one of the best months for continuing harvests, enjoying our gardens, and yes, preparing for the end of summer (sad face). Mark your calendar to get these gardening to-do’s done in your yard and garden.

Vegetable Garden

• Continue consistent watering practices. We might be cooling down, but we are still dry, so don’t let your hard work “die on the vine!”
• Plant fall vegetables! Some do really well in cooler weather and ripen quickly for harvest, such as lettuce, kale, arugula, Swiss chard, and spinach which can be direct seeded.
• Save heirloom plant seeds if you are looking to start your own plants for next season.
• Get your plant covers at the ready just in case we have a (pretty typical) cold snap or just in case temperatures dip lower than your veggies enjoy.
• Make sure to clear away any dead vegetation to prevent disease or pest proliferation.

mmmmm….the fruits of our labors. Photo by Valerie Podmore

Trees and Shrubs

• Water, water, water! Just like our vegetable gardens, our trees and shrubs need to be consistently watered. Weekly is a good schedule, but this fact sheet provides very thorough advice.
• Trim only branches or limbs which are damaged or diseased at this time.
• Be careful with fertilizing trees and shrubs. This link has good information on fertilization if there’s been particularly dry weather (when is it not?).
• While planting in fall might not be the #1 time, it’s still possible to find discounted plants and if you finish before the end of October, your tree or shrub will have some time to establish itself before the cold of winter.

Lawn Care

• Aerate this month to allow oxygen to get to the roots of your grass. This is an awesome turfgrass post for more information.
• Water deeply, giving your grass a good, long drink. Weekly for even 45 minutes is more beneficial than more often for less time.
• This great fact sheet has probably everything you need to know for keeping your lawn healthy.
• While the scourge of Japanese Beetles might be behind us, this is a prime time to apply grub-killers like grubGONE! and GrubEx to turf to help prevent them returning.

Perennial Flower Beds

• Water (I know, it’s like déjà vu!) weekly until the ground freezes to give the roots a chance to develop before winter.
• Cut back spent plants but consider leaving some stems and seed pods in place for pollinators and birds. This post from our Routt County Extension friends posits a different way of thinking about cleaning up (or not!) the season’s leftovers.
• Look at what needs filling in or doesn’t work and make plan for spring.
• Purchase fall planted bulbs – who doesn’t love plant shopping? This is the time that plant stores, catalogs or online sellers are stocking up so go crazy!

I can’t wait to shop! Photo by Pixabay

Annual Flower Beds

• Clean up annuals in containers and sanitize any pots you’ve emptied.
• Get some fall color such as chrysanthemums or pansies which overwinter quite well if mulched properly.

Other Projects

• KEEP WEEDING! That is all.
• Start prepping houseplants that have been outside to come back inside for winter. Check out this post for details.
• Finally, this is the month when Colorado Master Gardener program applications will begin! These will be posted on our main website with applications open September 1 – October 16. Do you or someone you know want to apply? Please DO!

Visit the CSU Extension Yard and Garden website (https://extension.colostate.edu/topic-areas/yard-garden) for more gardening tips.

Colorado Gardening Calendar for August 2022

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

The dog days are upon us, but with any luck, our gardens are still perking along without much assistance from us humans. With heat and drought still afflicting the plants, however, there’s still some garden mindfulness to practice before winding things down for the year.

The Monarch butterfly has fallen on hard times (Flickr)

WATERING

Nonxeric plants still require an inch to an inch-and-a-half of water each week in the August heat; without substantial rainfall, we’re stuck with manual or machine irrigation to keep gardens going for the time being. If our monsoon does kick in, inserting a water gauge in the garden to measure weekly precipitation totals will help limit irrigation to the proper amount for the season.

Keep an eye on sprinkler-system performance. Sprinklers should be sending water to plants and turf, not onto sidewalks, and amounts should be sufficient to dampen soil to a depth of four to six inches.

Check mulch to make sure that it’s still covering plant roots; it can be dislodged over time by humans, critters, and/or irrigation. Consider acquiring an extra bag or two (or more!) for use in the fall.

Discouraged by plants drooping in the heat? Don’t grab the hose and soak them immediately; if the soil around them is moist and mulching is sufficient, they have adequate moisture and should recover in cooler nighttime temperatures. And recent research on plants’ coping mechanisms when under stress will have a nice calming effect on the mind.

FERTILIZATION

Feed tomatoes, squash, and other flowering vegetables with low-nitrogen fertilizers as prescribed by their labels to promote continued fruiting. Don’t despair if production slows; fruit usually won’t set when temperatures exceed 80 degrees.

Feed roses for the last time in mid-August to prevent the growth of tender shoots that can be blasted by early frosts. Late-flowering perennials will appreciate feeding with slow-release organics through early fall. (Fall dieback of herbaceous perennials is part of their life cycle, so frost damage on new growth won’t be a concern.)

Castilleja in August bloom (Flickr)

WEEDING, HARVESTING, AND DEADHEADING

Keep after the weeds! They’ll continue to grow and set seed for next year if they’re not removed.

Continue to harvest ripe produce and clear a patch for a fall crop of cool-season plants like lettuce, radishes, and spinach – these can be seeded in mid- to late August. CMG GardenNotes #720 contains cultivation pointers for hardy and semi-hardy vegetables in Colorado. (Buy row covers and other protection from early frosts this month so you won’t get caught by the inevitable surprise September freeze.) Avoid the end-of-season rush by removing and composting healthy plants that have ceased fruiting.

Keep deadheading roses but gradually stop removing blooms to promote dormancy. If your roses make hips, this practice will also allow hip formation before frost.

PESTS AND DISEASES

Japanese beetles may have mainly disappeared by now, but August and September are prime months for applying grub-killers to turf. Get a start on control for next year by using products like grubGONE! and GrubEx.

Late-summer pests will annoy until cold temperatures kill them off or force them into hibernation, so check out this science-based advice from The Burlington Record for Front Range gardeners. July and August heat boosts development of powdery mildew and other plant and turf diseases; consult these Extension fact sheets for the lowdown on symptoms, causes, and remedies for the most common plant and turf disorders.

PRUNING

Taking out dead, diseased, and dying branches and canes is always in order – but take a look at this general guide on when to prune before wielding those Felcos. The general rule is to prune spring bloomers right after flowering, and summer and fall bloomers in spring.

Roses are happy with pruning in late April or early May. Many gardeners earmark this task for Mother’s day weekend, which is usually past the average last frost of the season. Find more on pruning roses here.

Hold off on pruning most trees until late winter, with four exceptions: maples, birches, walnuts, and elms – these “sappy” trees appreciate having their grooming in August.

PLANTING

Can gardeners plant trees, shrubs, and perennials in late summer? Absolutely, provided they do three things: select larger plants with good root systems, install them during the cooler parts of the day, and provide mulch and sufficient irrigation to establish them before the ground freezes (usually in mid-October at the Denver elevation). Nurseries will shortly begin their sales, so visit a few to see what you fancy.

Whatever you choose to do this month, County Extension offices are eager to help with your problems; give yours a call anytime!

Planning a Dry Shade Garden: Making Lemonade with Dusty Strawberries

Lori Williams, CSU Extension – Denver Master Gardener Since 2016

Bergenia cordifolia is well-suited for dry shade. Photo: Flickr

This is a dry shade garden story of happy accidents, fortunate timing due to 100+ degree temps, and purely unexpected research wrapped in a beautiful day at Denver Botanic Gardens Chatfield Farms.

After more seasons than I’d like to admit there is part of my yard that has silently been waiting for attention for many years. It’s fully dry shade, anchored with a lovely oak tree that has reliably made this space look pretty good despite lacking design and plantings, and receiving water only for the tree’s sake. Lackluster turf is more grayish than green and sparse to say the least. Hello Sad Spot, it’s finally time for your makeover.

With these hot temps I’ve retreated inside and have been pouring over xeric plant guides, watched the uber helpful presentation ‘Dry Shade Planning and Planting’ by Amy Lentz of Boulder County Extension, and investigated various garden designs and plant suggestions offered by the fine folks at Plant Select, Denver Water, and our very own CSU Extension.

The added bonus was finding myself immersed in a treasure trove of design and plant specimens at Denver Botanical Gardens Chatfield Farms a few weeks ago. Dry shade garden inspiration abounds!

A clear pattern of attack is laid out for not only dry shade but any new garden spot:

• plan ahead
• improve the soil
• limit turf
• efficient irrigation
• select plants
• mulch
• maintain

Plan ahead…hmmm…plan ahead….me? Oh but it’s a heat wave and due to travel plans and work obligations I’m doing research for a garden spot that I won’t be able to implement or plant until early fall. That sounds like I’m planning ahead!

Step one? Check! I even have time to have my soil tested.  And I’ll have time to actually amend the soil. This is going great! Look at me, planning ahead. It’s a new and different approach but I think I like it.

Next, I literally trip over one of the oak’s roots while collecting dusty soil samples and find myself looking at something that wasn’t half scorched turf but rather a mixture of barren and fruiting strawberries with yellow and pink blossoms. They were as dusty as the grass, but they’ve voluntarily planted themselves in this neglected space. Brazen little things! Congratulations, guys – you’ve just won the ‘Right Plant, Right Place’ award. Based on your gumption I decided on the spot that strawberries are the ground cover of choice.

I’ve spent time on cool mornings removing the patchy grass with my hori hori, providing more space for the strawberry tendrils to reach out and set roots. It’s delightful to see them take hold.

When Mother Nature gives you strawberries, make a strawberry lawn. Photos: Lori Williams

Thankfully, we have a sprinkler system, but the heads are all wrong (have been forever) for this area and I’ve been hose watering this dry shade zone instead for years. Once I fully determine the plants’ placement and they are well established, soaker hoses will replace the sprinkler heads to water the new guys more effectively. I’ll stick to the garden hose with my ancient frog eyed sprinkler during the establishment phase.

Photo: Lori Williams

One of my best-ever gifts from Mom was Denver Water’s series of xeriscape books.  They developed the whole xeric gardening concept to begin with, so Colorado-proud of them. Highly recommended reading!

Mulch selection is still a bit up in the air, but I am a diehard fan and believer. I feel like mulch is kind of the reward topper-offer at the end of newly planted garden spaces. It really makes things pop and look fully finished while stealthily helping manage weeds and providing moisture retention in the garden. Win Win Win!

As mentioned earlier, I happily found myself at Denver Botanic Gardens Chatfield Farm recently. I was expecting a lovely visit of course, involving a great stroll while surrounded by beauty. Perfect! Embarrassingly, I think I’ve only been to the arboretum for holiday lights during the winter.

This visit turned into Christmas in July as I opened my eyes and mind and phone camera – a dry shade plant selection opportunity extraordinaire! Lenten rose? Bergenia cordifolia? Siberian Bugloss? Now I only need to ‘weed’ through approximately 47 plants to select the 3-5 for my make over garden. But as I’m planning ahead, ahem, I have time.

Additional sources:

Kinds of Shade

Zero Water Gardening

Dry Shade Solutions

Selecting The Best Mulch For Your Plants

By Linda McDonnell, CSU Extension-Denver Master Gardener since 2013

Canva.com

Mulch makes an impact in so many ways – from water conservation to weed suppression, improved plant health to enhanced visual appeal – mulch seemingly has superpowers.

There are two general types of mulch – organic and inorganic.  Organic mulches include bark chips, straw, grass clippings, and dried leaves; gravel and small rocks are inorganic choices.  Which mulch to choose? The best advice is to match the mulch material to its intended use. Let’s take a look at some common mulch applications.

Shrubs, Trees and Perennial Beds

Bark Mulch

Three to four inches of bark mulch laid directly on the soil helps maintain moisture, reduce water use, and lower the soil temperature. Skip the landscape cloth and plastic barriers, which when left in place for multiple years, will impede water penetration, limit essential oxygen exchange, and inhibit root development.

Spring hyacinth bulb poking through bark mulch. Pixabay.com

Leave a few inches of bare soil around the base of the plant (more for large shrubs and trees) to allow the plant to absorb moisture. Avoid mounding mulch around the trunk of trees – a “volcano” of mulch will hinder healthy root development. Do not mulch over the root ball of a newly planted tree.

When adding plants to the bed, rake the mulch away from the space before digging to avoid mixing the bark into the planting hole. Bark chips break down in soil and as they decompose, can rob soil of essential nitrogen. 

How much mulch do you need? A two cubic yard bag of mulch provides three inches of coverage over 216 square feet. This online calculator is handy for determining the quantity needed based on depth and coverage area. It calculates the number of bags or bulk quantity needed, or at least gives a good estimate.

Pea Gravel

Gulley Greenhouse.com

Pea gravel (stones with diameters of less than one half inch) are highly effective mulches. Three inch deep coverage provides weed control and even more effective moisture infiltration than bark chips. During cold months, gravel mulch’s warming effect can increase biological activity down to one foot below ground, resulting in healthier, more resilient plants. Pea gravel is frequently the mulch of choice for xeric plants because it offers excellent drainage.

As with bark mulches, do not use landscape cloth or black plastic beneath pea gravel and move the mulch away from the crown of plants.

This Colorado State University (CSU) publication offers a complete review of mulch options; xeriscape mulches are discussed here.

Vegetable Gardens

According to CSU, “In general, mulching minimizes evaporation of water from the soil surface, reducing irrigation needs by around fifty percent. It helps stabilize soil moisture levels, thereby improving vegetable quality and encouraging the beneficial activity of organisms.”

Mulching also helps reduce soil compaction, can add organic matter to the soil, controls weeds, and modulates temperature extremes.  Bark chips are not recommended around vegetable plants but are useful as a garden path.

Black Plastic

Tomatoes, peppers, eggplants, and vines such as cucumbers, summer and winter squash, pumpkins, and numerous melons benefit from a layer of black plastic placed on the soil early in the season. The plastic warms the cool soil, allowing for earlier crop growth. Be sure to remove the plastic in the fall to preserve soil health. 

Early season zucchini plant in black plastic. Note the cutout around the plant’s base. Canva.com

Grass Clippings

Grass clippings from lawns that are untreated by herbicides or pesticides make excellent vegetable garden mulch. Build up the mulch coverage by adding up to a quarter-inch of clippings, allow them to dry, and then repeat with another layer. This layering process prevents the grass from forming a thick, impenetrable mat which restricts the plant’s moisture absorption.

At the end of the season, turn the grass into the soil; it will break down and add organic matter.

This CSU publication contains more options for mulching a vegetable garden.

Turf Alternatives and Garden Containers

Many are rethinking conventional bluegrass lawns and opting to use mulch to replace portions of turf. Large rocks, pea gravel, and bark mulch are popular landscape accents, paths, or borders that reduce water use and create an interesting, practical aesthetic.

Ornamental garden containers can be topped off with a layer of mulch to help retain moisture and add a finished look to the planter.

For a rewarding and plentiful garden, don’t skimp on mulch this season!