Colorado Gardening Calendar for May 2024

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

This is the month we’ve been waiting for! May is the best month for getting your plants from the Master Gardener Plant Sale on the 18^th and 19^th and planting them, with the caveat that anything can happen weather-wise, so be ready…remember 2 years ago?

Vegetable Garden

• This is the time to direct sow hardy, cool season vegetable seeds such as lettuce, kale, and spinach.
• Plant your (newly purchased!) veggies and herb plants when nighttime temperatures are consistently a minimum of 50 degrees, and make sure to protect them with cover when temps drop below 40 degrees. This includes tomatoes, peppers, and eggplants.
• Consider your planting location, i.e. Rotating your crops to prevent bacteria that might have infected plants last year from doing so again.
• Weeding is essential as much as possible, so let’s get on it!

Trees and Shrubs

• Just in case May ends up being sparse in the precipitation arena, don’t be afraid to bust out your hose and give your trees a good soaking, watering deeply once per week.
• This is also a good month to prune trees to remove any dead branches from needed but possibly damaging snowfall.
• Mulching is a great way of helping your tree retain water, just make sure to keep it between 3-4” deep and about 6” away from the trunks so it doesn’t hinder healthy root development and allows the plant to take up moisture.
• Prune summer blooming shrubs that bloom on new growth, such as roses before they begin to flower. Refrain from trimming shrubs that bloom on old growth such as lilacs until after they flower.
• This information sheet has great pruning information.

Lawn Care

• This is a great month to aerate the lawn to loosen up soil for better water absorption, as well as removing thatch (tight, brown, spongy, organic layer which can cause problems down the road in terms of lawn health) when it becomes too thick.
• After aerating is a wonderful time to overseed your lawn to regrow any bare spots which have developed over time.
• Watering is important for lawns as for other plants as this month heats up. Of course, if there’s rain or snow, hold off.
• Watering in the late evening or early morning helps retain more water as the weather tends to be cooler and more humid at these times.
• This is the month to treat your lawn for Japanese Beetle grubs. Use products like GrubGONE! which has been shown to do a great job of stopping this pest before it leaves your lawn and infests your plants.   

Perennial / Annual Flower Beds

• Continue cleaning out the garden, including spent flowers and cutting back foliage to help perennial plants direct their energy to growing.
• Look at possible locations where plants might not have performed as well as desired and where you can fill in or move existing plants.
• Waiting until late May to plant annuals will give them a chance to survive any crazy cold spells, although there are many that will do well in cool weather, such as petunias and pansies.
• This is also a great time to plant summer blooming bulbs!

May is such a great gardening month, let’s take advantage it and grow, grow, grow!

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

Colorado Gardening Calendar for March 2024

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

Snowdrops popping up through the snow (photo by Pixabay)

Hey friends, remember when it was January, and we were all lamenting how it seemed to never end? And then February was unseasonably warm and short, but Punxsutawney Phil did tell us early spring!  Well, celebrations are in order because it’s MARCH!

This is one of the best months for watching new growth come up and reigniting that gardening bug. Of course, there are other, more “productive” tasks to perform as well, so mark your calendar to get these gardening to-do’s done in your yard and garden.

Vegetable Garden

Coming soon to a veggie garden near you! (photo by Pixabay)

So, my first attempt at veggie gardening was “fun,” but because I’m not super into cooking it may have stopped me from being more attentive to my sad plants. That’s ok, maybe I’ll stick to flowers instead. For those of you who are more dedicated than I, take a look at some tasks below and know that gardening in Colorado usually requires the fastest-growing, most weather-hardy vegetable varieties.

• Clean out debris and replenish soil in vegetable beds while we wait for our seeds to start.
• Starting seeds indoors in March is perfect for any vegetables that should be planted outdoors in early April. Here is a list of seed companies if you are thinking of starting your vegetables from scratch.
• This link from The Old Farmer’s Almanac has all the recommended indoor and outdoor planting dates for vegetables and herbs.
• Think about layouts for your raised beds (if that’s what you’re using). This pdf has a lot of helpful information.
• Since spring seems to be coming early, vegetable garden water conservation might be a good topic to study.

Trees and Shrubs

Early spring Forsythia bloom (photo by Pixabay)

• Late winter/early spring are ideal times to trim trees, as explained on this page by the Colorado Forest Service.
• Precipitation in late 2023 was sparse, so it’s always a good idea to remember good watering habits for our trees and shrubs.
• This interesting article explains tree root systems and how our soil health, moisture and compaction (or not) can affect these very important plants.

Lawn Care

To lawn or not to lawn is becoming a much-discussed subject, given higher temperatures and lower precipitation amounts. Historically, many homes have yards planted with Kentucky Blue Grass lawns, which need more water, mowing and fertilization. This might be a good time to consider replacing your lawn with more native grasses (if you want to keep a lawn) or other native plants.

• In conjunction with Denver and other counties’ water providers, Resource Central has a lawn removal program to assist with moving to more natives.
• This is a great article about what native lawns can be planted instead of that water-hungry bluegrass.
• For those who want to keep their lawns as is (no judgement here!), mid- to late-March is a great time for aerating and general tidying.

Perennial Flower Beds

When I first became interested in gardening, I was – like all of us, I’m sure ­– in love with plants that were different looking, showy, flowering and easy to grow in places like Alabama, but not Colorado. I’m finally learning my lesson that it really is about the principle of right plant, right place. In addition, having listened to and read books and articles about the benefits of planting natives in our landscapes, I am becoming more attentive to what plants I choose for my landscape. I look not only for beauty, but regeneration and restoration. I mean who wouldn’t want to be part of a national movement like Homegrown National Park?

• Since I’m on my native plant kick, here’s a plug for these Colorado native perennials that can really enhance our landscapes and make them more sustainable.
• This is also a great month to start clearing out old, dead growth – as long as the weather is warm enough – to make room for shoots popping out of the ground.
• This page gives great information on perennial gardening so you can have everything prepped when you’re ready to put actual plants in the ground.

Annual Flower Beds

• Even though you can plant annuals pretty much anytime, they MOSTLY like being planted after last frost (usually around May 10-15).
• This is a great time to look at cool-weather annuals like pansies.
• The annual CSU Flower Trials have tested and found flowers that are hardiest and grow best through the tough, Colorado life. Check it out!

Make sure to mark your calendar for the May Denver Master Gardener plant sale (May 18 & 19) and visit the CSU Extension Yard and Garden website (https://extension.colostate.edu/topic-areas/yard-garden) for more gardening tips.

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.

Colorado Gardening Calendar for August 2023

By: Gail Leidigh CSU Extension-Denver Master Gardener since 2021

August is a fabulous month for enjoying your garden. Much of the work from earlier in the season will have paid off at this point. Since August is often hot and dry, it’s important to make sure your garden is getting the right amount of water, and to remain observant for stressed plants. Mark your calendar to get these gardening to-do’s done in your yard and garden.

Also this month and through September 15^th, CSU Extension is accepting applications for the next Colorado Master Gardener class. To learn more about our program, explore the resources at www.ColoradoMasterGardener.org and read Let’s Grow Together: Becoming a Colorado Master Gardener by Felicia Brower.

The vegetable garden at the Denver County Extension office. Photo: Merrill Kingsbury

A Yard and Garden Checklist for August

Vegetable Garden

• As your veggies ripen, harvest them, and if you cannot eat them right away, check out these good ideas to preserve them for later from Master Gardener Lois Margolin.
• How are your tomatoes doing? Growing tomatoes in Colorado can be tricky, with our wide temperature ranges and winds that prevent pollination. Some ideas for helping with your tomato problems can be found in this video on the PlantTalk website.
• Extend your gardening time by planting cool season vegetables such as peas, broccoli, and kale.

Trees and Shrubs

• Pay attention to signs of stress and desiccation in woody plants, and supplement with water as needed.
• Prune back summer blooming shrubs that have finished flowering, and that will bloom next year on this season’s growth. (It’s too late to prune spring blooming shrubs such as forsythia and lilac.)
• Always avoid trimming trees when they are water stressed by hot and dry conditions – they need to conserve all the energy they can this time of year.

Lawn Care

• During periods of high temperatures, a lawn may need as much as 2.5 inches of water or more per week.
• Mid to late August is a good time to over-seed bare spots in the lawn.
• The best defense against weeds in the lawn is thick and healthy grass, and you can encourage this by cutting the grass high – about 2.5 inches or higher.

Photo: Gail Leidigh

Perennial Flower Beds

• Some plants will start going to seed this time of year. If you don’t want the plant to self-seed, seed heads can be cut back. Or leave the seeds for the birds to enjoy.
• Weed ‘em and reap: Continue weeding the yard and gardens now, and reap the rewards later.
• Take note of what worked this year and what did not. Many perennials will be on sale at the end of summer and this fall, and it is a great time to fill in bare spots or replace plants that didn’t make it.

Annual Flower Beds

• Check the soil moisture in pots and hanging baskets frequently, as they will dry out quickly in the summer heat and wind.
• Clear and thin out plants that are fading, and make room for fall annuals that love the heat such as angelonia, ornamental kale, and daisy rudbeckia.
• Dead-head to encourage growth of new blooms.

Enjoy your garden this month!

Festival of the Unfamiliar: New and Under-used Plants for the Colorado Garden

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

One of the more rewarding aspects of gardening in Colorado is that a wide variety of plants can be grown here, even with our dry climate, high elevation, and unpredictable weather. The former advantage of selection, however, is often overlooked as we concentrate on coping with the latter disadvantages of our environment. We can remedy that by looking at resources (some with newly available and pending varieties) that will broaden our plant choices and result in more varied gardens that will succeed in our challenging climate.

Sulfur Flower

Desert 4 O’Clock

Buffaloberry

SPREAD A WIDE NET, FIND WHAT’S UNUSUAL TO YOU

Categorizing plants as “unusual” or “less used” is highly subjective and likely not useful to most gardeners. A rarely found plant also may be unsuited to our growing conditions. To avoid subjectivity and unsuitability, let’s look at resources that are sufficiently large and broad for gardeners to not only see the most desirable plant choices for our area but also decide what’s “common” and “uncommon” based on their own experience. 

To find many recommended trees, shrubs, and perennials that might fall into the “underused” category, consult one or more of these publications from CSU Extension:

• Low-Water Native Plants for Colorado Gardens: Front Range and Foothills – this includes many great plants for our area. Take special note of the little-used Gambel oak (Quercus gambelii), serviceberry (Amelanchier alnifolia), and desert four o’clock (Mirabilis multiflora) that make gardens both lovely and distinctive.

• Front Range Tree Recommendation List – see ratings of numerous selections for local gardens, including hints on suitability and cultivation. Many unusual, knockout plants are here.

• Xeriscaping: Trees and Shrubs – this fact sheet suggests desirable but uncommon woody plants like buffaloberry (Shepherdia argentea), Cheyenne privet (Ligustrum vulgare ‘Cheyenne’) and fernbush (Chamaebatiaria millefolium) that will thrive in a waterwise environment.

• Native Herbaceous Perennials for Colorado Landscapes – here we see favorites like Colorado columbine (Aquilegia caerulea) and blanket flower (Gaillardia aristata), along with the often-overlooked Maximilian sunflower (Helianthus maximiliana) and sulphur flower (Eriogonum umbellatum). 

Local and mail-order nurseries and horticultural websites love to present unusual and new offerings:

• High Country Gardens links to a page of unique plants on its website. Click on “Unique Plants” in the “Perennials” menu to see what’s available now – and be sure to scroll down to see plants that are out of season or sold out that may be available later. The HGC site also features 145 Plants for Colorado that will be unfamiliar to many visitors.

• The Colorado Native Plant Society website includes divisions of natives by life zone on its Colorado Plants and Habitats page. (Finding natives for sale can be tricky, but we can report that after a long search, the mountain ninebark (Physocarpus monogynus) finally turned up at a Denver nursery. A Google search for a plant by botanical name may also help to locate it on a nursery website.)

• The City of Boulder website offers a page designated as Native Plant Gardens Gallery and Growing Tips. As these recommendations are made for gardens in that area, check out the plant lists at Harlequin’s Gardens in Boulder to see if any are for sale locally. 

• Local nurseries stock many new and unusual native and adapted perennials, trees, and shrubs; visit your favorites in spring and fall to see what’s offered. Check their websites in spring for projected offerings.

• Mail-order catalogs are a treasure trove of new or rarely offered genera, species, and varieties that flourish here; avoid the big feeders and drinkers marketed for wetter and more temperate areas of the U.S. (Buy a plant from one company, and catalogs from the others will find their way to your mailbox.)

• Visit the popular website Dave’s Garden to find mail-order nurseries selling a desired plant in “Plant Scout” on the “Products and Sources” page. 

FOR THE NEW AND/OR SEXY, KEEP AN EYE OUT IN SPRING (AND FALL)

Bookmark these websites to get the first crack at what’s coming up in the spring:

• Search for suitable plants at Proven Winners;  their selections are popular at our local nurseries, and many will ship online.

• Use Monrovia to search by ZIP code and numerous other filters for plants that often wind up at local retailers, or order online for delivery to a local nursery.

• See new, well-vetted introductions and lots of advice from Plant Select every spring.

Have a question about this post (or anything else)? As always, please contact the Denver County Extension with your gardening questions.

Colorado Gardening Calendar for June 2023

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

June is my favorite month in the garden – from the explosion of colorful blooming perennials and the promise of the summer harvest to the comfortable temperatures – it just doesn’t get any better. We’re also coming off a month of record-setting moisture, which makes the landscape greener and lusher than usual.

Early June columbines, coral bells & tulip foliage. Photo: Linda McDonnell

Our May gardening calendar covered the season-long essentials of weeding, mulching, and watering. Refer to it for those tips. On this post, let’s look at ways to keep plants healthy, troubleshoot potential issues, and enjoy the garden.

Trees and Shrubs

• Check apple, crabapple, mountain ash, and pear trees for fireblight, a bacterial disease that emerges in spring, especially when there’s been wet, warm weather. Look for curled, bent shoots with brown or black leaves, and limbs shaped like a shepherd’s hook. Learn how to properly treat fireblight here.

Fireblight on an apple tree. Photo:  I, Paethon via Wikimedia Commons

• Suckers are shoots that spring up from the base of the tree trunk or root system. Aspen, sumac, chokecherry, and plum trees are prone to suckering. Suckers can indicate the tree is stressed. Hand prune suckers where they attach to the trunk or root system. CSU reports Sucker Stopper RTU™ may help with control.

• Prune spring flowering shrubs now to control their size/shape, remove dead wood, increase air circulation, and improve flowering next year. Find tips here.

Vegetables and Herbs

• CSU’s Grow & Give program is a way to share your harvest with the community. Consider signing up to donate excess produce on the Grow & Give website. You’ll also find excellent growing tips and insect/disease help on the site.

• If you’re growing in containers, remember that they dry out quickly. Check daily as temperatures rise. Mulch will help retain moisture.

• For the best flavor, remove flower buds from culinary herbs.

It’s hard to pluck lovely chive blooms! Photo: Pitsch from Pixabay

Perennials and Spring Flowering Bulbs

• When flowers fade, snip tulip and daffodil flower stems at the base. Leave the foliage until it yellows and goes limp. As it dies back it’ll provide valuable nutrients to the bulb which will help with next year’s flower production. Apply bulb food now too. If you already pulled the foliage, you could still add fertilizer.

• Deadheading, or removing flowers that have finished blooming is a matter of personal preference. Deadheaders cite encouraging re-flowering, creating a tidier landscape, and reducing unwanted reseeding as motivators. Others prefer a more natural appearance that provides food and shelter for birds and other animals, reseeds freely, and features interesting seed heads. Many gardeners deadhead some, but not all plants.

• If you deadhead perennials, consider the plant’s growth habit when pruning. For example, cut the flower stem about ¼” above the next set of leaves or an emerging bud on upright clumping perennials such as echinacea. Shear mounding plants – such as catmint, golden storksbill, and cranesbill geranium – down to about three inches. This is quick and easy. They’ll look scruffy but rebound quickly.

• Ornamental grasses and most climbing roses bloom once a season so deadhead for aesthetics or to remove diseased foliage.

Shear golden storksbill to get more flowers & contain size. Photo: Linda McDonnell

• To keep mid to late season blooming perennials from flopping, reduce their height by 25-30% in early to mid-June before flower buds emerge. This Chelsea Chop promotes side branching, creates shorter, stockier plants, and delays flowering by a week or two. Good candidates include soft stemmed, clumping plants such as New England aster, chrysanthemum, and false dragonhead.

Manage Unwelcomed Visitors

• Creeping bellflower (Campanula rapunculoides) is prolific in Denver. Treat it as a weed. Unlike other campanula species, it’s a fast growing, sharp elbowed invasive that will choke out any plant in its way. It has heart-shaped leaves at its base, which become narrower as they move up the stalk, and green to reddish stems. Mature plants have stubborn, deep, white fibrous roots. Left unchecked it can reach three feet tall and produce nodding light blue bell-shaped flowers on one side of the stem. Control by digging out the roots and removing new growth as it pops up. If you’re plagued with this thuggish plant, this handout from Wisconsin Extension is a must read.

You’ll regret letting creeping bellflower get this big! Photo: Linda McDonnell

• Aphids are back. These soft bodied, green, tan, or orange sesame seed shaped insects are relatively harmless to shade trees and ornamental plants. They suck on tender young foliage and mark foliage with a sticky honeydew secretion. Lady beetles, green lacewings and parasitic wasps feast on aphids. A strong stream of water may be enough to dislodge aphids without compromising biodiversity. Insecticidal soaps can also be effective.

• Aphids on food crops can be more problematic. See this University of Utah article for advice.

• Rabbits are cute but can be destructive to plants and turf. Find tips for creating barriers and using safe repellants here.  

• Japanese beetles will emerge from the ground in late June or early July. Get ready to pick and drown or stomp them. Review CSU’s report for details and watch for our July JB post for helpful tips.

Lawn Care

• Water only when needed and in compliance with Denver Water Department’s rules. CSU’s lawncare handout can help you use water responsibly while maintaining a healthy lawn.

I hope you enjoy this beautiful time of the year. Remember to visit the CSU Extension Yard and Garden website https://extension.colostate.edu/topic-areas/yard-garden) for more Colorado gardening tips and solutions.

Colorado Gardening Calendar for April 2023

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

A reminder to resist the urge to plant frost-sensitive flowers and veggies this month. Ice encapsulates this blooming tree in mid-April.

As the saying goes, “April showers bring May flowers.” But in Denver, where one day the snow flies and the next day is sunny and 70, April is mostly a planning and prep month here. It’s a hopeful and exciting month for gardeners, filled with possibilities and dreams that this year, “I’m finally going to [fill in the blank] in my garden.” For me, it’s that I’ll finally install drip irrigation vs. hand-watering my vegetables and flowers. For you, it may be planting trees for some much-needed shade or creating your first vegetable garden. Whatever your goals, following is a guide to help keep your April gardening tasks on track.

Vegetable Garden

• Clear debris from last year’s garden and any winter mulch covering the bed, such as dead leaves. Pull any emerging weeds, which are easier to deal with early in the season.
• When the soil is dry, not wet, or muddy, add a fresh 2-3-inch layer of compost to your beds. This will greatly support soil health and the vigor of your plantings. 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 any planting begins.
• Plant frost-tolerant spring plantings, such as peas, spinach, arugula, radishes, Swiss chard, etc. You may wish to soak your pea seeds in warm water prior to planting for faster germination. 
• If you haven’t yet started indoor seeds for warm-weather vegetables such as tomatoes, peppers, squash, melons, etc., now is the time. 
• Reference this Vegetable Planting Guide to plan for what you will plant when. 

Trees and Shrubs

• Continue hand-watering your trees and shrubs, particularly if it is a dry April.
• Early this month, prune deciduous trees and shrubs. 
• Remove broken branches from trees. Clear away dead leaves and decayed fruit from the base, as they can house unwanted inspects and pathogens. 
• I’ve sadly been noticing a lot of tree removal in my neighborhood lately. Denver needs a more robust, healthy tree canopy. This is a great month for planting new trees, selecting varieties that best suit Denver’s climate. Here is a guide to successful tree planting. If you’re in the market for a tree, check out the Park People’s annual tree sale on April 22, which supports the Denver Digs Trees program.

Lawn Care

• Prep your mower, sharpening the blade as necessary and conducting any other necessary maintenance. 
• If you use a pre-emergent weed product, apply before weed seedlings – particularly crabgrass – sprout. Targeted weeds can vary by product.
• Fertilize as desired, reading labels for proper application.
• Denver Water recommends waiting to turn on your irrigation until after the last freeze, typically in early May.

Perennial Beds

• Cut back perennial plants if this wasn’t done last fall, leaving 3 inches of the plant above the soil.
• Plant asparagus, rhubarb, berries, bare-root roses. Soak any bare-rooted plantings for a few hours prior to planting.
• Pull emerging weeds now, staying on top of them early in the season.
• Divide perennials that are overgrown, such as chives, sedum, grasses, phlox, daisies, hosta, etc. This will lead to healthier plants and better growth. It will also allow you to give away new, inexpensive perennial plantings to your neighbors and friends. 

Other Thoughts for April Gardening

• Inventory and prep garden supplies. Sterilize and sharpen garden tools. 
• Sow wildflower and pollinator seed mixes.
• Consider and plan for any trellising that may eventually be needed for your vegetable and perennial gardens.
• Be prepared for frosts and bad weather. Have sheets of plastic and old bedsheets nearby your garden for quick tarping in case of late-season snow or hail.

I hope this list makes tracking all of the April garden to-do’s a bit simpler. And remember this about April: attentiveness and proper planning for your landscape and gardens now means less work and hassle, and more ease and enjoyment, as your summer gardening season progresses.

Organizing and assessing  tools and supplies needed for the gardening season.

Dealing with Winter Storm Damage to Trees and Shrubs

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

Photo credit: Pixabay.com

During mild weather, we relax and admire our gorgeous lilacs and viburnums, fertile fruits, and long-lived majestic street trees. With the coming of the colder months, however, we become aware that these lovely friends are susceptible to damage and even death from sleet, high winds, and heavy wet snow. The effects of this weather are a constant concern on the Front Range, but with a little forethought and planning, they can be mitigated (if never eliminated). 

Effectively dealing with storm damage requires planning that begins when a gardener is considering installing trees and shrubs. (Minnesota Extension offers some great information on dealing with tree damage based on this principle.) However, as most readers of this blog are probably here seeking advice after a catastrophe, let’s do some time-traveling and begin with should be done (and not done) immediately following a storm and conclude with some hints for encouraging plant survival in advance of nasty weather.

This post features the highlights of emergency tree and shrub care; review the article ‘Caring for Storm-Damaged Trees’ from the Colorado State Forestry Service for more thorough guidance.

• During a heavy snowfall, brave the flakes to gently shake accumulated snow off tree and shrub branches with a broom. Lift each branch from the bottom instead of poking or shaking it. (Be prepared to do this more than once.)
• Before going out, look at the yard and street: are power lines down, are there dangling tree branches threatening to drop, or is debris or ice covering the turf or the walks? Any one of these can present a hazard to gardeners working outside. Above all, assume that any power line lying on the ground is live. 
• Examine the damage: look for leaning, broken, or uprooted trees and shrubs. Determine if there are holes and cracks in bark, trunks, or roots. Note the state of the crown (branches and foliage) of each tree; loss of more than 50% of the crown may require tree removal. 
• Leave ice coating the branches alone; it will melt as soon as temperatures rise above freezing.
• Damaged bark can be removed back to the point where healthy bark appears.
• Don’t top a damaged tree; you’ll render it weaker and more susceptible to disease.
• Avoid painting holes, wounds, or pruning cuts; the plants will seal and heal by themselves.
• Small tree branches can be removed by the gardener (see the fact sheet ‘Pruning Shade Trees’ linked below for details) but allow an arborist to remove large branches. 
• Leaning shrubs and small trees can be moved back into position, staked, and mulched.
• Wait until new growth appears to fertilize.
• Inevitably, friendly visitors bearing chainsaws will appear, offering to repair your tree and shrub damage “for less than those big companies.” These are the horticultural equivalents of gypsy roofers who show up after hailstorms. They are usually untrained and not covered by workers’ compensation or liability insurance.

Now, let’s examine how we can minimize storm losses with some deterrence.

Mitigating plant damage begins with asking what genera, species, and varieties of trees and shrubs display less vulnerability and more resilience in the erratic Colorado climate. Luckily, the ready answer is (drum roll……) native and adaptive plants. Plants that have evolved in montane, submontane, or plains environments will rebound from weather damage much more quickly and thoroughly that those imported from dissimilar growing conditions. Plan for resilience by selecting trees and shrubs recommended in these resources: 

• Native Shrubs for Colorado Landscapes
• Native Trees for Colorado Landscapes
• Front Range Tree Recommendation List
• Tree Selection: Right Plant, Right Place
• Plant Select

Once plants have been selected, practice proper siting and planting. Again, we’re assisted by Extension and Plant Talk resources:

• Preparing the Planting Site
• Tree Placement: Right Plant, Right Place
• Planting Trees and Shrubs

Proper cultivation and integrated pest management (IPM) are indispensable to plant health, as outlined in these publications:

• IPM and Plant Health Care
• When to Fertilize
• Watering
• Pruning Shrubs
• Pruning Shade Trees

For information on specific plants, diseases, and pests, review the resources on subjects from “abnormal and distorted plant growth” to “Zimmerman pine moth” included in the Extension page Online Gardening Publications (Trees and Shrubs). 

Fans of Gardener’s Supply Company should check out the great discussion of winter damage prevention on their website.

We hope that this is helpful in the present emergency and beyond – but, as always, Denver County Extension is eager to help with all problems and concerns!

Looking Forward: A Lower Maintenance Garden with Native Plants, Fruit Trees, and Shrubs

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

Now that the 2022 summer season is winding down, it’s a great time to review what worked in the garden and what didn’t and to start planning for next year. (Keeping a garden journal throughout the season saves time and makes this much easier!)

Start by asking yourself the following questions:

• What grew well this season?
• What didn’t grow as well as you would have liked? Any idea why?
• Did you struggle with pests or disease?
• What do you want to plant next year?

After you have the answers to those questions, you can begin to make a plan to fix any problems that popped up or to repeat your successes next season.

As far as what grew well in my garden this year goes, I planted more localized seeds this year because seeds bred for our specific climate tend to have fewer days to maturity and produce more drought-tolerant plants than ones grown from other seeds I’ve used. They fare better in my garden and will be a staple every year moving forward.

Photo credit: Felicia Brower

That being said, my garden got off to a rough start this year thanks to pest problems, extreme heat, and watering issues. Many of the seedlings I started inside were immediately eaten after being transplanted outdoors, and it seemed like no amount of diatomaceous earth could help. I wasn’t watering enough to combat the weeks of 100° sunny weather, and the growth of a lot of my vegetables suffered because of it. I was recently able to get things under control (better late in the season than never!) and my vegetables and flowers have finally started growing the way that I had hoped they would. I’ll be spending the winter learning more about Integrated Pest Management (IPM) and effective watering techniques to make the most of water during a drought.

As I look at what I’d like to change in my garden next summer, one big one is that despite loving it, I want to spend less time doing maintenance in it. I spent much more time weeding and trying to problem solve than I would have liked, and a few adjustments could make a very big difference.

The biggest change is going to be adding more native herbaceous perennials and fruit shrubs and trees in the yard. My hope is that by making the investment to fill out those open spaces, the weeds I spent so much time pulling will be unable to take over, and I’ll end up with beautiful, lower-maintenance native flowers, shrubs, and trees.

Here are a few of the plants on my list for next year:

FLOWERS

I usually plant vegetables and annual flowers, but after seeing the perennials that I planted last year pop up this year without having to start anything inside, I’m making a big shift to focus on native flowers and herbs that come back without any effort from me.

Blanket flower. Photo credit: Canva

Having perennials show up in the spring will add much-needed greenery to the yard after a cold winter, and I look forward to the pops of color they’ll provide throughout the summer and into fall. I can’t get enough of the vibrant red and yellow petals of blanket flower (Gaillardia aristata) and plan on adding some big patches of it to my garden next year. I’ll also be looking into adding more penstemon (Penstemen spp.) to the landscape. With more than 60 native penstemons to choose from, these easy-growers range in size from a few inches to a foot or two tall with long flowering spikes.

Chocolate flower. Photo credit: Canva

Chocolate flower’s (Berlandiera lyrata) yellow daisy-like flowers have a wonderful scent and typically flower from June until frost. Goldenrod (Solidago spp.) produces tall bursts of yellow blooms later in the summer, from August until November and is known for being easy to grow and care for.

SHRUBS

Shrubs, specifically ones that produce fruit, are going to take a lot of space in my yard next year. Drought-tolerant gooseberries and currants grow especially well in our area, and their berries can be eaten fresh or used to make delicious jams and pies.

Gooseberries. Photo credit: Canva

I have a raspberry patch that I plan on expanding to different areas of the yard. These prolific growers will take up a lot of space and provide delicious snacks while I’m out harvesting and fresh berries for some new recipes I want to try. Serviceberry is cold-hardy and drought-resistant, making it a no brainer for someone looking for a low-maintenance addition to the garden. The fruit also happens to be high in vitamins and is comparable to blueberries but with a slight apple flavor.

Serviceberry. Photo credit: Canva

TREES

Trees are a big investment and a lot of planning needs to go into which trees will be planted and where. For fruit trees, I’d like to plant plums, since they’re considered very dependable for this area, and a peach tree. Peaches can be a higher risk tree because late frosts can damage blooms and prevent peaches from developing, but I think it’d be fun to have a self-fruiting dwarf variety that can still provide shade and habitat for animals even when it’s not fruiting.

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After planting all of the fruiting trees and shrubs, I’ll have an abundance of produce in my yard for years to come that I’ll be able to preserve and share with neighbors and members of my community through programs like Grow & Give. It’ll take a few years, but after everything’s established, I’ll only need to worry about planting my vegetables annually, which I also plan to scale back on…eventually. For now, my focus is on finding the plants that I want to get in the ground this fall and next spring, filling out the landscape, and learning as much as I can about how to help everything in my garden thrive.

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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 their gardens.

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!