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.

Colorado Gardening Calendar for November 2022

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

Anything can happen in a Colorado November: our first hard freeze (or the second or the third), or nighttime temperatures stuck at 45F. Lawns and gardens can suffer from heavy wet snow (with the splintered tree limbs littering the streets to prove it) or prolonged dryness that has gardeners alternating watering with leaf raking. Despite the unpredictability of autumn, winter will eventually arrive (probably with two feet of snow on Thanksgiving Eve), so our focus this month is on closing out the 2022 season and preparing for Spring 2023. 

VEGETABLES

• Harvest any remaining vegetables; we can have a killing frost and/or snow that will wither produce anytime now. Farm Calculators offers an extensive list of veggies for autumn harvest; if mild weather has gifted us with green tomatoes, try ripening some to use on Thanksgiving! Minnesota Extension has compiled some great hints on harvesting AND storing late-season produce.
• Finish cleanup now while temperatures remain mild. Pests and diseases will overwinter in plant debris and afflict the garden next spring and summer – and no one feels like working outside in a December snow squall!
• Spread compost over the soil and turn it in – it feeds the microscopic critters that will deliver nutrients to your plants’ roots next year.

TREES AND SHRUBS

• Pruning trees and shrubs can wait a few months, according to the schedules outlined in the Plant Talk articles Pruning Shrubs and Pruning Shade Trees. Dead tree branches, however, should be removed ASAP so they don’t become a hazard in heavy snow accumulations. (Many arborists offer discounts for off-season services.) Ditto for all dead bits on shrubs and roses.
• Keep watering weekly until the ground freezes – usually around Thanksgiving at Denver’s elevation. 
• Check mulch levels to ensure that soil moisture remains adequate to maintain healthy roots. Mulch should cover the root balls without crowding the stems or trunks. 
• Irrigation during winter warm periods is also key to helping roots support plant growth next year. Consult the Extension Fact Sheet “Fall and Winter Watering” for details on winter watering.
• Wrap the trunks of trees too young to have formed bark to prevent sunscalding during periods of alternate warming and freezing in the winter. During warm periods, tree trunks take up water into their cells, which then burst when temperatures drop below freezing, killing bark and conductive tissue. “On at Thanksgiving, off on tax day” is a good rule of thumb for utilizing tree wrap.
• Consider using protection like plant bags and burlap around evergreens prone to drying out in winter winds. 
• Put rose collars around your roses and fill the collars with leaves for insulation, or mound soil over the bud union of each plant.

PERENNIALS

• Make sure that nonxeric and new xeric/native perennial plants are mulched to a depth of at least one-and-a-half to two inches. Pull the mulch back from the crowns to forestall crown rot and discourage pests from burrowing around the plant.
• Keep watering perennials until the ground freezes and throughout the winter as prescribed by the fact sheet referenced above.
• Postponing deadheading and cutting perennials back until spring offers several advantages to your garden: many perennials produce seedheads and stems that offer cold-weather food and shelter to birds, beneficial insects, and other wildlife; intact stems also protect crowns from freezing and catch snow to deliver more moisture to the plants. 
• It’s a bit outside the recommended planting time, but If you still have bulbs to plant and the soil is workable, do it now. Since roots will have less time to develop, flowering may be reduced, but you still may enjoy spring blossoms. Make sure to water them in well. 

LAWNS

• Rake up leaves so they don’t mat on the turf and promote mold growth. Running a mower over piles of leaves will produce free mulch to spread over plant beds (and free nutrients as the leaves decompose)!
• Blow out and shut off sprinkler systems if you haven’t done so already. If time and weather permit and the turf looks dry, irrigate one more time.

MISCELLANEOUS

• Clean, sharpen, and oil tools; get that lawnmower blade sharpened while you’re not distracted by spring gardening tasks.
• Consider what plants to add next year – gardening catalogs will start arriving next month! And continue to contact Denver County Extension with all your gardening questions.

ONE MORE THING

It’s been my pleasure to contribute to this blog this season, but my short posts can cover only a few essentials. Therefore, here’s a fall task list that not only adds another dimension to your fall garden experience but also allows me to make a small homage to a most distinguished horticulturist whom we lost this year: Ten Key Tips for the Fall Garden.

Colorado Gardening Calendar for October 2022

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

Woohoo October! Photo by Pixabay

It’s Pumpkin Spice time…no, not the drink, the gardening season! October is one of the best months for cleaning up the garden in preparation for the impending end of the season and of course doing pumpkin things! Mark your calendar to get these gardening to-do’s done in your yard and garden.

Vegetable Garden

• Continue to harvest your vegetables which you planted both earlier in the season and in early fall.
• Think about building cold frames or some sort of protective covering to help your veggies last as long as possible with the colder weather this month.
• Cover crops can help build your soil for next year’s planting.
• If (unlike me) you have kept your herbs alive this season, maybe give herb preserving a try.
• Take a look at this article about Pumpkin Habanero peppers…talk about Pumpkin SPICE!

Trees and Shrubs

• Young trees’ trunks (2” and less) will need to be wrapped to protect from sunscald in winter (from November to April).
• Pay attention to watering, making a plan to water deeply every 4-6 weeks during dry fall and winter months.
• More detailed tree and shrub care information can be found here.

Lawn Care 

• Lawn aeration can still be performed early in the month.
• Because we can have our first frost of the season anytime this month (average first frost is around October 6^th), this is time to winterize your sprinkler system. Good advice even if you don’t do this yourself. 
• Oh hooray! LEAF CLEANUP.
• In addition to the above, here is the Leaf Drop information for 2022 in Denver.

Perennial Flower Beds 

• If you didn’t plant any spring blooming bulbs yet, get ‘er done this month! 
• Early in the month is a great time to divide and transplant summer blooming perennials before the cold moves in.
• Here is a great pollinator-friendly post on fall garden clean-up if you are looking to help our friends through the winter.
• Working on winterizing your plants will help them survive for next year’s growing season.

Annual Flower Beds

• Pansies are a great way to get late season color into your garden.

Other Tasks

• Houseplants that were outdoors will want to come back in when the nighttime temps fall below 50 degrees. Make sure to give them a good clean-off of creepy crawlies before bringing them inside!
• Clean your tools for next year.

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

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!

Colorado Gardening Calendar for July

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

Spring sprang (along with a surprise 19 hours of snow in late May), and now midsummer heat has descended. The major gardening tasks are in the rearview mirror, but that doesn’t mean that there aren’t some things left to do, irrespective of the summer temperatures!

Our keywords for July are observation, assessment, and maintenance. Focus on these tasks for continued garden success.

WATERING

Typically the monsoon kicks in around mid-July, so smart irrigation will be a priority this month.

Check the mulch around perennials, trees, and shrubs to make sure that it’s in place over root balls (not against the stems) and that it remains at the recommended depth of two inches. Replenish mulch if needed. Infrequent, deep watering of these plants will produce the best results. Non-xeric plants, especially roses, require an inch of water weekly during hot periods; soak the areas around the bases of new xeric plants twice a week to promote root growth. 

Check the soil of annuals, fruits, and veggies to a depth of one inch, and water if the topsoil is dry. Mulching will reduce the frequency of irrigation, discourage weed germination, and prevent soil compaction as you move around the plants. Container plants generally require daily watering.

DON’T wash off pollen by spraying the foliage of tomatoes, squash, and other fruiting plants that require fertilization.

Try the “footprint” test to determine when turf should be irrigated: if grass remains flat after being walked on, it’s time to water; otherwise, wait a day or two. Watch the spray patterns of your sprinkler heads to make sure that water is landing evenly on the turf and not on sidewalks. (Uneven irrigation is a likely cause of brown spots in the lawn.)

If plants are given proper irrigation and mulching but droop in the daytime, don’t rush to turn on the hose – many plants wilt under high heat and revive overnight. Nevada Extension has contributed some good hints for coping with stressed-out plants.

FERTILIZATION

Fertilization schedules and amounts vary widely between types of plants, so this topic is therefore highly complex! Right now, plants like tomatoes and summer-blooming perennials will require regular feedings to promote flowering, but shrubs and trees can take a break until fall or even next spring. Research fertilization requirements of plants when in doubt, and check labels for rates and times of application.

See the Extension fact sheet Fertilizing the Vegetable Garden  for information on food crops. 

WEEDING, HARVESTING, AND DEADHEADING

Get the weeds as soon as you see them; the bigger they are, the more difficult they are to remove and the more likely to set seed as they mature. If using products like Roundup (glyphosate), apply in the early mornings or on days when the temperatures reach no higher than 80 degrees. Foliage won’t absorb these products in extreme heat. 

Harvesting of many vegetables and fruits can begin this month per this table from PickYourOwn.org; for others, we’re still in the observation and maintenance modes. Pick fruit and vegetables in our cool mornings.

Deadhead both summer-blooming plants (to promote budding) and plants that have finished flowering (to keep them tidy). Remove spent blooms on lilacs early this month to allow the plants enough time to set buds for next spring.

PESTS AND DISEASES

Keep an eye out for foliar damage, stunted growth, holes in produce, and distorted fruit and blossoms; these indicate the presence of pests and disease. Pests tend to be species-specific, while diseases like powdery mildew afflict plants across a wide spectrum of genera and species. CSU Extension’s site features a great page listing their resources regarding insects (including beneficials); the “Yard & Garden” page includes fact sheets devoted to garden diseases. There’s also a searchable Online Resources for Gardening and Landscape page that directs users to all gardening pages, including blogs with updated information.

When using pesticides, make sure that their application won’t harm beneficial insects. Carefully follow all label directions for usage.

Japanese beetles will begin infesting our favorite plants this month. Many systemic insecticides are harmful to our pollinators; the safest and most reliable methods for control continue to be handpicking/drowning and applying products containing bacillus thuringiensis var. galleriae (Btg) to plants. (Btg will not kill the beetles immediately but will reduce their numbers over time; it’s also included in products like grubGONE! that can be applied to turf containing the grubs in late summer.) The ever-popular and useful Extension fact sheet “Japanese Beetles” offers numerous suggestions for dealing with these pests.

As always, County Extension offices are eager to help when problems emerge; give them a call anytime!

Colorado Gardening Calendar for May and 2022 Denver Master Gardener Plant Sale

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

May is the month when gardening really goes into high gear! Here are the areas and tasks to tackle this month:

VEGETABLES AND HERBS

• Mark your calendar for the return of the Denver Master Gardener Plant Sale on May 21-22 at Harvard Gulch Park. The selection can’t be beat if we do say so ourselves! For more information visit: Upcoming Events – Denver County Extension (colostate.edu).

• Veggies and herbs can be planted this month; be prepared to cover them if nighttime temperatures go below 40 degrees. It’s advisable to plant tomatoes when overnight temperatures are consistently above 50 degrees.

• Start weeding now, in all areas of the garden. Get ‘em while they’re young!

• Consult the Extension fact sheet Fertilizing the Vegetable Garden to determine if and when to apply fertilizer to your plants.

• Find hints for combatting vegetable pests in this list of CSU fact sheets.

LAWNS

• Make sure that hoses and sprinklers are in good condition; apply an inch of water to the lawn each week, except during rainy periods. Denver Water has some excellent suggestions regarding lawn irrigation and general care from May 1^st through September 30^th, when watering restrictions are in effect.

• Consider irrigating the lawn at night or in the early morning hours when evaporation is minimal. This can be a real turf AND water-saving measure in the hotter months, and it won’t promote diseases.

• Set mower blade height at two inches – higher grass keeps the soil moist and promotes good root growth.

• A thick thatch layer interferes with efficient watering and fertilization, so check for thatch and arrange for power-raking if the thatch is at least one-half inch thick.

• Products like GrubGONE! that contain bacillus thuringiensis var. galleriae (Btg) as a control against Japanese beetle grubs must be applied to turf in May and early June to take effect. Check with a local nursery regarding availability of these products or order them online. Consult this Extension fact sheet regarding Japanese beetles for advice on dealing with this pest throughout the summer.

• How lawns are watered, mowed, cultivated, and fertilized in their early growth will determine their appearance and health throughout the summer and fall (and perhaps for the next year as well). This fact sheet on lawn care outlines the best practices for tackling these tasks from now until fall.

May garden in Sunnyside, Denver. Photo by Terry Deem-Reilly

TREES AND SHRUBS

• Take a look at the garden to spot any “holes” that can be filled with a good-looking shrub, rose, or small tree – right now is when nurseries have the best selection. Be sure to call the Utility Locator Service at 811 before digging any large holes.

• Begin watering existing trees and shrubs deeply once a week and check to ensure that plants are well-mulched. Here’s helpful information on selecting the correct mulch for your plants.

• CSU Extension has published a tree recommendation list for the Front Range and fact sheets on native trees and native shrubs that can be helpful in deciding what to add to your garden.

• Start checking for pests; they will become more active as the weather warms and our spring rainfall commences (we hope). Consult this list of CSU fact sheets for information on specific insects and controls. When selecting pest controls, consider their effects on beneficial insects!

• Now’s the time to apply copper spray to susceptible trees such as apples, pears, quince and crabapples, to prevent fire blight.

• Finish spring fertilization and pruning of roses; make sure to apply two inches of mulch at the base of each plant and water newly planted roses twice a week for the first two or three weeks to promote root growth. Once established, roses will appreciate getting at least an inch of water weekly as temperatures rise.

ANNUALS AND PERENNIALS

• Perennials can be hardened off and planted now; wait until at least the last average frost date in mid-May to fill annual beds and containers. Keep frost covers handy if we have one or two chilly nights before Memorial Day.

• Summer bulbs can be planted now, so check them out at your local nurseries. It’s also a great time to divide summer and fall blooming perennials, find excellent info here.

• Treat pollinators by seeding bare spots with their favorite annual plants, including borage, dill, zinnia, and/or cosmos. Plant as recommended by the seed packets and water. Seeds will germinate in a week or two; sprinkle the seedlings gently every few days and wait for the bees and butterflies to arrive! More pollinators mean more tomatoes, squash, fruit, etc., etc.

May certainly is a busy month in the garden! What’s on your to-do list?

Colorado Gardening Calendar for April and Grow & Give 2022

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

April is one of my favorite months in Colorado, a time when signs of life are everywhere –– trees are budding, the crocus and daffodils are in bloom. Mostly empty garden beds beckon, promising beauty and bounty for the next six months. And, while the garden to-do list is long, I feel inspired to tackle each task and eager to be back in my garden.

Having a monthly “to-do” gardening list helps break down the many gardening tasks into less overwhelming chunks, reminding me what to do when. April is a great time to get your gardening ducks in a row, peruse your favorite gardening centers, prep your gardening soil for planting, and begin putting a shovel and seeds in the soil. 

A Gardener’s Yard and Garden Checklist for April

If you haven’t done it yet, it’s time to finish cleaning up of last year’s garden, removing any annual plant remnants, cutting back perennials and pulling early emerging weeds. Clear any mulch, such as dried leaves laid last fall over vegetable beds or around perennials. Add compost if you didn’t do it last fall. When the soil is mostly dry and workable, add 1-2″ of compost into your soil at a 3-5″ depth.

Also consider testing your soil. It’s not too late! I wrote a blog post last January about getting your soil tested. Testing is the best way to fully understand what your soil needs to growth healthy plants.

Here are some additional April gardening “to-dos” in Denver: 

Vegetable Garden

• Plant cool weather seedlings such as broccoli, cabbage and cauliflower. Want to grow asparagus or rhubarb? Now’s the time to get those perennials into the ground. 
• Direct sow early season veggies and greens, such as arugula, peas (I soak in warm water in advance for quicker germination), spinach and radishes. Water well if rain is sparse. 
• Plan for snow and hail. How will you try to protect your early plantings? It’s always good to have some old bed sheets or plastic near your garden in case a late winter storm or spring hail passes through. 

Arugula pops up early in the garden. Photo by Molly Gaines

Peas can take a late-season snow. Photo by Molly Gaines

Trees and Shrubs

• Look closely at your trees for any winter damage that may need an arborist’s attention. Inspect shrubs and other perennials for signs of life. Take note of plants that should be showing initial green or growth but are instead brown and brittle. This way, you can inspect again in a few weeks and determine if they need replaced. 
• Start planting both shrubs and trees if the ground is thawed. Water thoroughly.

Lawn Care 

• Check your irrigation to be sure your system is working. Your lawn needs 1″ of water weekly. 
• In early April in Denver, or by the time forsythia is blooming, apply pre-emergent herbicides to prevent summer crabgrass.

Perennial Flower Beds 

• Remove any dead foliage still lingering from last season and pull early-season weeds.
• Divide perennials that have grown too large for your space or haven’t been divided in a few years. It’s good for the plant and your budget! You can store in pots and water until you’re ready to plant elsewhere in your yard or give them away to neighbors. 
• Sow some wildflower seeds for flowers pollinators will love later. Water well. 
• New growth for roses can typically be seen as April progresses. Prune canes that are damaged or dead and then all others (except climbing roses) to 12” to 24” above ground. 

Daffodils are a quintessential April flower in Denver. Photo by Molly Gaines

Annual Flower Beds

• Start planting early-season annuals that can tolerate light frost. Consider pansies earlier in the month and flowers, such as snapdragons and sweet alyssum, later in April. 

(For additional April gardening tips and ideas, check out the CSU Extension garden calendar for April 2017.)

Grow + Give Program

If you’re a Denver vegetable gardener, start thinking now about joining CSU’s Grow + Give, a modern victory garden project. The goal of the Grow and Give program is to help address food insecurity in Colorado.

If you commit to the program now, you can plan to plant a little extra to donate to your neighborhood food pantry, neighbors in need, or other organizations that accept excess produce. Visit growgive.extension.colostate.edu for details. Watch for the 2022 season sign up; it should be posted soon. 

Colorado Gardening Calendar for March

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

Crocus, the harbingers of spring! Photo credit: Pixabay

MARCH is one of the best months to whine about WHY ISN’T IT SPRING YET? then calm down, realize it’s almost here and daydream about sunny days in the garden. As I write this, there is still snow on the ground and more in the forecast (which is awesome sauce for our outdoor plants) but if you are like me, the instant March hits you think it’s time to get outside doing garden things. Slow down there cowboy, technically it’s still winter and there’s more planning and prepping to be done. Mark your calendar to get these gardening to-do’s done in your yard and garden.

Vegetable Garden

• Time to get your project management hat on and plot out your garden. You’ll find a plethora of landscape design apps online or you can use good old paper and pencil.
• Inventory your seeds and order any you might still need as well as any supplies for seed starting. 
• Cold tolerant veggies can be started in a cold frame or possibly outdoors if the daytime temperatures are consistently 40 degrees F or above – so pretty much the END of March.

Trees and Shrubs

• If precipitation is sparse (4 weeks without moisture), remember to water your trees and shrubs.  While we are doing well moisture-wise this year,  we know things change quickly in Colorado!
• This is a great time to prune summer flowering shrubs and dormant/shade trees. However, refrain from pruning early flowering shrubs such as spirea, lilac, and forsythia because they bloom on last year’s growth. 

Lawn Care 

• Early March is a great time to sharpen up your mower blades (try to contain your excitement!) and add or replace oil if applicable.
• If the ground is not frozen and your landscape not too dry (i.e. LATE March), you can aerate, which is the process of poking holes in the lawn and supplying the grass with air.

Perennial/Annual Flower Beds 

• Just like your veggies, get your seeds in order and ready to start them sprouting indoors.
• Check your bulbs and tubers in storage and think about what bulbs you can plant in spring for summer blooms.
• As with February, take stock of your current beds to see what might be lacking and needs new life. 
• Don’t worry too much about late season snow, as snow serves as an insulator on perennials that have broken dormancy and won’t harm plants.
• If you attended the Colorado Home and Garden Show in February, use the ideas you gained to plan for any changes you want to make. However, remember the motto of “right plant, right place” when planning your new additions.

Finally, (the bane of my current existence) review structures and hardscape, paying attention to needed repairs or changes. With luck this year my money tree will bloom profusely and help me pay for everything! 

Don’t forget to visit the CSU Extension Yard and Garden website for more gardening tips…and happy gardening!

Colorado Gardening Calendar for February

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

Frozen February Leaves. Photo credit: pixabay

February is one of the best months for planning for spring (aka daydreaming about blooming plants and wonderful veggie gardens!), looking after your indoor plants, and continuing to take care of your outdoor plants and lawn during low water periods. Mark your calendar to get these gardening to-do’s done in your yard and garden.

Vegetable/Flower Garden

Begin planning which seeds you are going to start in spring. It’s hard not to get over-excited and overwhelmed (I am just writing this blog) by all the seed choices so try to be strong! Here are some great articles about that process: 

• Get Ready, It’s Almost Time To Start Seeds
• Top Ten Best Management Tips for Starting Your Garden from Seed
• Want to grow your own transplants? Well it is almost time to start
• Catalog dreaming

Trees and Shrubs

• Take stock of garden plants to decide which to keep, discard and/or tidy up.
• Do any necessary late winter pruning. 
• Remember that even during the winter, our landscapes need watering if we haven’t received much precipitation.

Lawn Care 

• This is the period to perform lawn clean-up such as a light raking to remove stray leaves, twigs, dead growth, and winter debris. This allows sunlight and air into the soil to encourage growth.
• As before, if there’s a lack of precipitation, consider watering when the temperatures are above 40 degrees with no snow cover, at mid-day to allow water to soak into the lawn.

Perennial/Annual Flower Beds 

• Think about what plants you might add to your flower beds. To get you in the mood for choosing new plants, take a look at the CSU Flower Trials site. It’s kind of like a Hunger Games for flowering plants (just kidding), where they follow the progress of specific cultivars over a three-year period to see which have proven to be most adaptable for the Front Range of Colorado. 
• Late February is an ok time to plant cold-hardy annuals such as pansies, if the weather is nice enough.
• You might be tempted to start working the soil in preparation for planting but wait! It’s still too cold for the soil (and you honestly), as it will cause damage to the soil structure this early. 

Indoor House Plants with obligatory “Lucy the plant sniffing doggo” by Val Podmore

Indoor Plants

• Let’s not forget the wonderful indoor houseplants we might have, and continue to tend them but remember, be careful not to overwater. Don’t just water on a schedule. Check the need for water based on feeling in the soil down to at least the first knuckle (about 2” down into the soil in more than one location) or use a moisture meter. Sometimes being a good plant parent means tough love.
• This is also a good time to wipe them down to clean off dust and help their leaves to breathe.
• Just as people tend to “slow down” in winter (think “too cold to go out so I’ll sit on the couch and become a potato”), so many of our plants also slow in their growth. Winter is a period of dormancy for many of them. In the main, try to refrain from fertilizing at this time as it will upset their natural cycles of growth and dormancy.

Of course, you can always visit the CSU Extension Yard and Garden website for more gardening tips.