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.

Winter Reading for Gardeners

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

It’s too late for fall planting, too soon to start next year’s seeds. For the next few months, especially after the holidays, gardeners are likely to get restless. With gardening tasks mostly on hiatus, it’s an ideal time to dive into a great garden book to learn something new, hone your skills, or dream up your next project.

Here are some titles to check out, recommended by members of the CSU Extension and Master Gardener community. All are chock full of information, presented in interesting, useful ways.

Hope you find something for yourself or to give a fellow plant enthusiast this holiday season.

Photo: Alison O’Connor

Dirr’s Encyclopedia of Trees and Shrubs, By Dr. Michael Dirr

Recommended by Alison O’Connor, PhD, CSU Extension Professor of Horticulture, Larimer County Extension.

“This book is incredibly comprehensive and lists all of the common trees and shrubs in our landscapes – and those not-so-common, plus cultivars. And it’s actually funny! Dr. Dirr has a great sense of humor about his experiences with these plants and tells some great stories. Maple the Beagle also enjoys this book – especially the Acer selections.”

(Dr. Dirr is the author of the respected Manual of Woody Landscape Plants, another excellent resource.)

Amazon.com

High and Dry, By Robert Nold

Recommended by John Murgel, CSU Extension Specialist – Horticulture and Natural Resources, Douglas County.

“Dry humor permeates the most thorough reference on truly dry gardening in temperate climates that I have ever encountered. Gardening ‘theory,’ experience, and an extensive plant list keep this book from gathering dust on my bookshelf.”

Amazon.com

Meet the Natives: A Field Guide to Rocky Mountain Wildflowers, Trees, and Shrubs, By M. Walter Pesman, revised and updated by Dan Johnson

Recommended by Merrill Kingsbury, CSU Extension, Master Gardener Program Coordinator, Denver County.

“The book’s subtitle is ‘Bridging the Gap Between Trail and Garden’ and it definitely delivers! I’ve used this book successfully when looking for native plants to add to my own garden. It details over 400 plants organized by flower/foliage color. The photos are excellent, too.”

Amazon.com

RHS Latin for Gardeners, By Lorraine Harrison

Recommended by Cassey Anderson, CSU Extension Specialist, Adams County.

“This book features gorgeous illustrations and definitions of the reasons behind Latin binomial nomenclature, revealing origin, growing conditions, color, shape, form, etc. hidden behind the Latin terminology. So much information is locked behind the Latin language and this book helps to unlock it.”

Archive.org

Wood and Garden, By Gertrude Jekyll

Recommended by John Murgel, CSU Extension Specialist – Horticulture and Natural Resources, Douglas County.

“The full title of Wood and Garden: Notes and Thoughts, Practical and Critical, of a Working Amateur says it all. While many sniff at the old-fashioned design advice provided by Gertrude Jekyll or balk at her sheer Englishness, I find this and her other titles to be the perfect escape to another world, particularly on winter nights. Jekyll’s vivid language is transportive and inspiring. Published in 1901, you can find the whole thing online at no cost here if you can’t procure a printed copy.”

Image: Felicia Brower

Dig Deeper: A Five-Year Garden Question-a-Day Guided Garden Journal, By Felicia Brower

Just published by this blog’s contributor and Denver County Master Gardener Felicia Brower, this guided journal helps gardeners connect with changes in the garden – day-to-day and throughout the seasons. Every day, you’ll get one question that encourages you to briefly pause and reflect on your efforts and the experience of creating a garden – regardless of size. It’s perfect for experienced and newbie gardeners alike.

Have a favorite garden book? Please tell us about it in the comments!

And finally, happy holidays from all of us who make this blog happen. We’re taking a few weeks off and will be back in the new year.

Winter Conifer Care for Year-Round Interest

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

Conifers! They occur naturally everywhere in Colorado (albeit less so at plains elevations under 6700 feet). And they’re everyone’s go-to tree or shrub for filling a hole in the landscape or adding hassle-free continuous color. They’re so numerous and large that we often forget that their successful cultivation requires more than finding suitably large and sunny spots for placement and marveling at their spectacular (and automatic) growth. There are, however, some steps to maintaining these gorgeous plants in the dryness and cold of Colorado.

First all, let’s define the term “conifer”: it’s basically a tree or shrub with needles that produces seeds in the form of cones. Find a thorough discussion of the division Pinophyta/Coniferophyta here.

Planting

A winter care routine begins with planting properly: take a look at CMG Garden Notes Tree Selection: Right Plant, Right Place before shopping for a tree or shrub. (This publication includes a link to the Front Range Tree Recommendation list.) Conifers generally prefer sunny sites and good drainage, but moisture needs vary by species. Determine how much watering you’ll need to do to maintain the health of your plant – including winter watering so be sure to consider access to a water source when selecting a location.

Next, make sure that the planting site is large enough to accommodate a mature plant; that cute Colorado blue spruce in its three-gallon nursery pot will eventually reach a height of 30 to 60 feet and require enough room for a 20-foot spread. Consider if a mature tree will interfere with power or water lines, or property access. Remember that winter dryness can take a toll on evergreens, so place it in a sheltered spot or take steps to prevent desiccation (more on that later). Mulching to keep roots cool and moist, especially during initial growth, is a must.

Selection

If you like the look of a particular species but can’t find enough room in your garden for it, look for dwarf varieties. If your planting options are limited to containers, check out Monrovia’s The Best Conifers for Containers (and How to Care for Them). If you’re planting in the ground but would like to stay strictly native, read the CSU Fact Sheet Native Trees for Colorado Landscapes (remember that natives have the advantage of NOT having to adapt to our growing conditions while they’re establishing themselves in the landscape).

Monrovia offers some good suggestions for selection, planting, and care in Your Complete Guide to Growing and Caring for Conifers (this is a commercial site, so be prepared to see lots of their stock!).

Initial Care

Once the plant is in place and (we hope!) flourishing, maintain care throughout the season as outlined in CMG Garden Notes Care of Recently Planted Trees. Consult the CSU Fact Sheets for Trees and Shrubs for specific advice on planting, pruning, watering, and diseases of conifers and other woody plants. Proper irrigation is especially important, so water when the soil around the tree is dry to a depth of one inch. Continue irrigation throughout the fall.

Winter Care

Needle desiccation in the winter months can occur at the Denver elevation when precipitation levels are low, and plants aren’t receiving supplemental watering. Water all perennial plants, trees, and shrubs to a depth of one inch when the air temperature is above 45F and the soil is unfrozen.

Be aware that not all needle desiccation and drop result from insufficient watering; many species shed needles naturally at periods ranging from one year to every 17 years. Deciduous conifers such as larch and bald cypress drop all of their needles in the autumn. If needles in the center of a tree such as a pine turn brown, that’s normal shedding, but browning at branch tips is a concern. Take a look at the CSU Fact Sheet Environmental Disorders of Woody Plants for more information on this subject.

Many Front Range gardeners love arborvitae and despair at their seemingly inevitable winter damage. Wrapping the plants in burlap and/or using a protectant like Wilt-Pruf® or CloudCover® can help, but as noted above, the best protection for vulnerable plants is proper siting. Plant arborvitae and other tender conifers on the lee (downwind) side of the garden, or next to a house or shed. Remember that plants can cope with a variety of situations, even temps of -15F and extended dry periods (with some help). Good luck with your winterizing!

Experimenting with Winter Seed Propagation

By Lori Williams, CSU Extension – Denver Master Gardener since 2016

 I hope my winter experiment yields beautiful Echinacea plants this summer! Image: Flickr

I’m a fan of the gardening podcast “A Way to Garden” hosted by Margaret Roach, columnist for The New York Times. Recently she interviewed Heather McCargo, founder of the Wild Seed Project, a horticulturist-supported non-profit based in Maine. The organization is committed to building awareness of native plants, the importance of increasing biodiversity, and ethical seed collection. Find the full interview here.

Their discussion of outdoor winter seed sowing really piqued my interest. Had I ever given much thought to winter sun, precipitation and temperatures being necessary for native seeds to germinate? Honestly? No. 

The suggested timing for winter seed propagation – start after the holidays – also caught my attention. It all sounded pretty simple. Start by gathering on-hand garden supplies and seeds collected from my yard and other gardeners and find an appropriate winter location for the pots to live. The genuine bonus of growing a few of my own perennials was just too intriguing not to try. I was inspired!

Everything needed for winter propagation of seeds that not only survive winter but germinate because of winter. Photo: Lori Williams

Materials

• Containers roughly 4-8” wide, avoid biodegradable pots as they will likely break down in winter weather.
• Seeds – discover germination guidelines and other seed information for Colorado here.
• Organic, compost-based potting soil is recommended because it’s filled with different microorganisms. Please note, compost is not recommended for Colorado native plants as they prefer a ‘leaner,’ less organic soil. Find info on propagating our regional natives here and in CSU’s fact sheet 7.242.
• Coarse sand to cover seeds after planting assists seeds in staying lodged in planting medium and allows light to reach them.
• Group containers, flats, etc. and cover with wire screen, anchored with bricks or rocks, for squirrel protection.
• Label pots to avoid forgetting what seeds were planted where. Pencil on plastic tags really does work best.

January 17th was 38℉ & partly cloudy, a cold breeze bringing in a big snow, I wanted my seeds to benefit from the predicted precip. Photo: Lori Williams

Location

• A level, shaded area for containers to endure winter undisturbed. Shade is essential during sunny, warm days so pots don’t overheat and dry out. Keep containers level so seeds don’t float or splash out during heavy precipitation.

Ethical Seeds

The Wild Seed Project stresses collecting and using seeds native to your location. Collecting native seed from public lands and in the wild (in Maine, Colorado, and most of the nation) is typically a huge no-no (AKA unethical) so how do we collect seeds ethically? 

• Seed from our own gardens are the easiest to collect. 
• The friendly approach of asking ‘May I gather a few seeds from your XYZ perennial? I’d love to try to grow it.’  
• Seed swaps are another excellent resource and a request on social media can produce great results. 
• Wild Seed Project and other ethical seed providers offer native seeds for purchase. 

Buy seeds suitable to your growing conditions, of course, and be familiar with what those plant seeds look like. As a newbie gardener, I planted dried Echinacea flower petals twice thinking they were seeds. 

My Project

While I did not have native seeds for my backyard experiment, I did have ethically collected seeds from non-natives. I planted three flats with Echinacea and lavender seeds from my garden and seeds from a divine lupine that was a volunteer in a friend’s yard. On January 17th I placed my pots in deep shade against the house with bricks holding the screen cover in place. That evening 6.5” of snow fell and temps stayed cold for weeks afterward. 

Snow covered since January 17^th, it took the snow on my flats until the end of February to finally melt. Photo: Lori Williams

Outdoor winter propagation is challenging for the impatient gardener (me) but my long game of possibly growing some perennials of my own from seed has me hopeful. With more Colorado snow and cold ahead, my flats remain undisturbed in the shade. I resisted the urge to water them during the last several weeks of no moisture – and then we had a welcome icy rain turning into snow – YES! 

As my flats have yet to show any noticeable growth, I am watching for signs of success during our longer days accompanied by the sun beaming from higher in the sky. 

How to Select and Pamper Your Houseplants this Winter

By Lori Williams, CSU Extension – Denver Master Gardener since 2016

Orchid in full bloom at Denver Botanic Gardens. Photo: Lori Williams

Houseplants are so lovely and offer a nice spot of green during the Colorado winter. Almost everyone, and certainly gardeners, can find them an enjoyable extension of outdoor gardening. Be it herbs in a kitchen window, plants brought in from summer’s patio to overwinter, or the many varieties that prefer an all-year indoor existence, research shows several health benefits of houseplants, including:

• Improve employee focus and reduced sick days in the workplace.
• Reduce fatigue and boost indoor air quality.
• Lift spirits – pops of color from seasonal plants such as amaryllis or orchids can help beat the winter blues.

As with all plants, houseplants subscribe to the maxim: Right plant, right place. Many who are convinced they have a brown thumb can work through the following simple steps, find their right plant within their (right) place and achieve success. It’s not magic, complicated, or mysterious. Promise.

TIPS FOR HOUSEPLANT SUCCESS

Proper lighting is most important. Evaluate your space and select plants that will work. Find tips for evaluating light quality here.

Most houseplants like household temps that most people like, basically around 70℉.

Some plants need more humidity than typically found indoors, so grouping those together on pebble lined trays and adding water to below the top of pebbles increases the relative humidity.

Watering is unique to each plant: Overwatering kills as many plants as under watering.  Plant tags and a quick google search can explain your plant’s preference. Grouping plants with similar watering needs together helps water accordingly. An inexpensive houseplant water meter is a handy tool, too.

Monitor consistently for pest and/or disease (and while shopping for them, too).  Look under leaves for yellowing or leaf loss. Discovering new growth can happen here, too!

Fertilize seasonally, usually during active growing months from April through September.

SELECTING HOUSEPLANTS

If you are new to houseplants, find help selecting the best ones for your lighting and skill level. This webinar is absolutely wonderful for explaining the science behind happy houseplants and selecting the right plant for your place.  

Once you’ve got a handle on the light in your space, it’s on to the fun part: Make a wish list of suitable plants and go strolling through your favorite local garden center. Enjoy the immersion in the elevated oxygen of the greenhouse, ask their staff questions, and peruse the gorgeousness you will find. 

Aesthetically, it’s fun to mix up plant structures – tall and reedy, soft and velvety, draping growth habitat, foliage colors. Are you wanting something that blooms? Violets, bromeliads, or cyclamens might be the ticket. Or is self-sufficiency key? Sansevieria, pothos, schefflera or succulents are rewarding lower maintenance options.

Another tip is to inspect plants before you buy by checking under the leaves and at the soil line. Sometimes creepy crawlies sneak their way in to even the most professional greenhouses!  

Boston fern, schefflera, and sansevieria on spa day. Photo: Lori Williams

WINTER TLC

Regardless of the time of year, all houseplants need a little TLC. During winter months, with non-melting snow, dreary skies and almost freezing temps projected for days – houseplant pampering can perk up plants and us – their peeps! Here’s how I do it:

• Gather the basics: Gloves, clippers, potting mix, a small fork or chopstick, fertilizer, watering can, and a bowl of water to keep any clippings hydrated for propagation.
• Collect plants in the shower or tub and gently spray or splash off the mid-winter dust.  It’s a nice humidity boost for them, too.
• Soak soil thoroughly and let the container drain. Clip, pluck or pinch off dead, diseased, or discolored matter. If the foliage is looking a bit limp or weak you can fertilize lightly with half strength of your favorite brand.
• Inspect plants for disease and pests. If any are present, you’ll find remedies here.
• This is a good time to select plant parts for propagating and prune to reshape foliage. Check out good tips here.
• Gently disturb the top 1” of container’s soil and apply a top dressing of potting mix. Depending on your plant’s preferred growing conditions, this can also be a good time to repot root bound varieties.
• Return the plant to its home. Every few weeks, rotate the plant so it receives even light on all sides.
• Dispose of diseased matter rather than composting it to avoid spreading the disease further. Compost temps need to reach at least 150℉ to kill pathogens which is a struggle for home compost bins to reach during winter months.

TLC for Asparagus fern – though fluffy looking, it is surprisingly thorny. Use gloves! Photo: Lori Williams

Houseplants offer a verdant element to our homes and workplaces. They are as varied and interesting as the people who share them!

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!

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 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.