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!

Colorado Gardening Calendar for January 2023

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

January is typically a restful period for gardeners – a  time to pour over seed company websites or catalogs, review last year’s successes or blunders, set goals for the upcoming season, and investigate new gardening topics. But even though we may be ‘armchair gardening’, it is important to keep a watchful eye for issues that crop up in the landscape. Don’t forget to occasionally stroll through the garden, especially after storms, to inspect trees and plants. Take care of any issues as soon as you’re able to avoid complications later.

It’s a cold and snowy start to the new year!

Let’s take a look at recommendations for the month.

Trees and Shrubs

• We’re huge proponents of winter watering, but thanks to a sloppy, moisture-rich late December snowstorm, watering may not be needed in January. This could begin to change later in the month though, so monitor conditions with special attention to new plantings. Four weeks without sizeable moisture is the signal to drag the hoses out.

• Regularly examine trees and shrubs for snapped limbs and bark damage due to snow loads or heavy winds. This post offers tips on preventive maintenance and dealing with damage.

• Winter is an ideal time to have large deciduous trees pruned professionally. The City Forester maintains this list of licensed contractors; pointers for hiring a tree care company can be found here.

• De-icing salts used on nearby sidewalks can cause leaf scorch on evergreen broadleaf shrubs, brown needles on conifers, and damage to turf roots. Use with care.

Manhattan Euonymus (Euonymus kiautschovicus) is a broadleaf evergreen shrub prone to leaf scorch Photo: Linda McDonnell

Perennials

• Add additional mulch around perennials that are heaving or lifting up from the soil. Heaving is caused by repeated freezing and thawing, often occurs in newly planted perennials with young root systems, and can indicate compacted soil. Left unattended, it can damage or kill plants. Come spring, organic matter may be needed to improve drainage. According to the University of Iowa, shasta daisy, (Leucanthemum spp.) and coral bells (Heuchera spp.) are particularly prone to heaving.

Pixabay.com

Seeds

• Take stock of your seed stash – the prior season’s seeds may still be viable. CSU’s fact sheet on storing veggie and flower seeds has a helpful chart on seed longevity.

• While it is still a bit early to start seeds indoors, it’s not too soon to replenish seeds and supplies at a local garden center or online. Or set up a seed swap with your gardening buddies.

• If you’re new to seed starting or want a refresher, check out this blog post for a thorough tutorial so you are ready to go when it’s time.

Denver’s Recycling and Compost Programs

• Denver’s ‘green cart’ compost program rolls out citywide this month. Meat and produce scraps, coffee filters, and greasy pizza boxes, in addition to garden waste, are just a few of the tossable items. If you already participate in the program, be sure to encourage green cart newbies to give it a try.

• Have old, unused, or unwanted pesticides or herbicides hanging around? Here’s info on Denver’s program for the safe disposal of many hazardous materials  A nominal fee applies.

 Learning Opportunities

• Managing Squirrels in the Landscape on January 11th from 12-1 pm is the first in CSU’s series of virtual garden workshops. For a list of all presentations and to register, visit https://csuhort.blogspot.com/p/csu-extension-spring-gardening-webinars.html.

• The Colorado Garden & Home Show returns to the Colorado Convention Center February 4-12^th.  In addition to workshops, extensive plant displays, and vendor information, Colorado Master Gardeners will be present to answer gardening questions. Tickets available now.

• Audubon Rockies and Cheyenne-High Plains Audubon Society hosts the Landscaping for Water Realities on the High Plains conference on February 4^th.  Virtual attendance is free. Program and registration info here.

• Email garden and plant questions with descriptive photos to Denver Master Gardeners at the Denver Botanic Gardens gardeninghelp@botanicgardens.org.

• CSU’s Extension website is always available to provide science-based gardening information. It’s a good one to bookmark.

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 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.

Winter Watering

By Uli Klein, CSU Extension – Denver Master Gardener since 2019                                                

After the fall clean-up is complete and our sprinkler systems are winterized, it’s easy to think the gardening season is over and it’s time to bask in the late autumn sunshine. Because the visible parts of plants go dormant in late fall, it is very easy to overlook the importance of off-season moisture. But to ensure the health and longevity of the landscape, it’s wise to keep an eye on the amount of moisture received during the next several months. In Denver, relying solely on fall and winter precipitation alone can be insufficient for trees, shrubs, turf, and perennials.

According to the graph above, the average amount of annual precipitation in Denver is ~14 inches and varies significantly from year to year. For example, we received 26 inches of precipitation in 2015, but only 9.5 inches in 2020. November through February are often the driest.

How does lack of moisture affect trees and plants?

Under continued dry conditions, the delicate hairs on feeder roots can eventually be permanently damaged and unable to absorb water or transport nutrients. Most root hairs are in the top 12 – 15 inches of the soil and often extend beyond the dripline. These roots provide moisture to the upper parts of the tree. If these structures cannot supply enough water, leaves will wilt at first; and if drought conditions continue or worsen, twigs or entire branches may die. This loss of branches is a tree’s attempt to resize the canopy in relationship to how much water the roots provide and is called dieback. I’ve often spotted dieback on trees in Denver parks. This University of Kentucky article further explains how dry seasons affect woody plants.

Evergreen affected by drought conditions. Photo by Uli Klein

In the spring of 2020 many Denver trees, especially pines and arborvitae, died from a combination of pronounced temperature swings, unseasonably cold temperatures, and a mid-winter drought. Signs of stress are not typically visible until spring, when evergreen needles yellow or drop, or in severe cases, plants are lost.

Tree with minor dieback. Photo Uli Klein

Tree with major dieback. Photo by Uli Klein

Newly planted trees and shrubs are particularly vulnerable to extreme conditions and need extra TLC during the cold seasons. To fully establish, trees generally need one growing season for each inch of trunk caliper. During that time, they are particularly sensitive to lack of moisture, temperature swings, and strong, drying winds.

Herbaceous perennials can also suffer from lack of moisture, although the damage is less eye-catching than that exhibited by shrubs and trees. While it is easier and less costly to replace a perennial than a large tree or conifer, replacement plants will likely be smaller, take time to establish, and are unnecessary expenses.

Our lawns will also benefit from watering during prolonged dry periods of 4–6-weeks. Find tips for winter care at Lawn Care – 7.202 – Extension (colostate.edu).

When deciding how much to water, take local factors into account: A good layer of mulch reduces evaporation and helps plants to retain more moisture, while those in more wind-prone sites and/or facing south-west require extra moisture. BTW: 10” of average snow, 4 to 5” of wet snow, or 15” of powdery snow are equivalent to 1” of rain.

Let’s recap the facts

• In Colorado, the winter months (November through March) are often the driest.
• Precipitation varies from year to year – monitor local weather conditions.
• Make newly planted trees, shrubs, and perennials a priority since they need more moisture than established ones.
• Don’t forget that your lawn needs extra water.
• Healthy trees and plants are an asset that are under-appreciated until they need to be replaced.

Tips for winter watering

• Water only when it’s above 40°F, ideally around midday so the water is absorbed before nightly temperatures dip.
• Apply a gentle stream of water, either from a watering can or a hose with a watering wand, so the water soaks in and doesn’t pool.
• In dry conditions, all plants (trees, shrubs, perennials, turf) benefit from extra water from October through March. Pay particular attention to recently planted specimens or those in windy locations or south-west exposures.
• A good layer of mulch reduces watering needs.

How much water is needed?

Trees

• Approximately 10 gallons of water per each diameter of the tree trunk per month (i.e., a 2” tree needs ~20 gallons/month) distributed at several locations within its dripline.

Shrubs

• Newly planted:  approximately 5 gallons every 2 weeks.
• Established <3ft: approximately 5 gallons per month.
• Established >6ft: approximately 18 gallons per month.

Final thoughts

Preparing this blog has really motivated me to do the right thing for my plants this winter season. I hope that it will convince you, the reader, that winter watering is worth the effort and preserves precious plants. Therefore, fellow gardeners, keep your watering can at the ready!

Additional references

https://www.canr.msu.edu/news/how_do_trees_survive_in_the_winter

https://extension.colostate.edu/topic-areas/yard-garden/fall-and-winter-watering-7-211/

https://planttalk.colostate.edu/topics/trees-shrubs-vines/1751-fall-winter-watering-drought/

Growing Garlic in Colorado

By Felicia Brower, Master Gardener Apprentice, Denver County Extension

(Photo credit: Matthew Pilachowski)

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

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

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

Choosing Garlic Varieties

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

Hardneck

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

Softneck

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

Planting Garlic

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

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

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

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

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

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

Harvesting Garlic

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

Curing Garlic

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

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

Grow Greens Indoors this Winter

January can be a tough month for gardeners. Thumbing through seed catalogs is a nice diversion for a while, but then what?

Instead of using your green thumb to turn pages in a catalog, you can stretch it with a couple of easy indoor gardening projects. Each of these projects takes minutes to plant, and in a few weeks you’ll have something delicious, green and growing in your kitchen. You probably already have most of the supplies to get started today.

Planting Garlic Greens

While this indoor herb planting won’t grow garlic bulbs, you’ll get several cuttings of tall greens. These greens add a delicate garlic flavor to stir fry dishes, green salads or any favorite recipe.

Materials:
Small container of potting soil
Saucer to catch excess water
Garlic cloves (old or new)

Instructions:
1. Place a paper coffee filter to cover the container hole.
2. Fill container with potting soil and add water to moisten the soil.
3. Separate the garlic into individual cloves; leave skin on.
4. Arrange the cloves in the container, planting 1-2 inches apart.
5. Push cloves into the potting soil, about 2/3rds of the way in, pointed end up.
6. Water in; place the container in a window or spot with indirect sunlight.
7. Keep soil moist and you’ll see the garlic sprout in about a week or so.

When the greens are 6 inches tall, clip and use. The cloves will keep growing for at least several more cuttings.

Planting Micro Greens

Micro greens can be planted outside in early spring, but they can grow indoors, too. These small green leaves are tasty and nutritious when used to top green salads, sprinkled into sandwiches instead of lettuce, stirred into omelets or any other way you’d like to eat them.

Materials:
1 packet micro green mix or sprouting seeds like broccoli or pea (check with your favorite garden center, natural grocery store, or order online)
1 shallow plastic container with holes punched in the bottom (like a clear lettuce or spinach container, minus its lid)
1 tray or second container to catch any excess water
Loose, well-draining seed starting mix or potting soil
Spray bottle

Instructions:

1. Punch small holes in the bottom of the container for drainage; cover holes with paper coffee filters. Place the container on tray to catch drips.
2. Fill container with several inches of soil (about 2 or 3 inches).
3. Moisten the soil; allow excess water to drain and discard.
4. Scatter seeds over the top of the soil; cover with a thin layer of soil.
5. Use a spray bottle to moisten seeds.
6. Place container on a sunny windowsill or under grow lights placed several inches above the top of the plants.
7. Keep soil evenly moist, but not overly saturated; don’t let seeds dry out.
8. Look for seeds to sprout and grow their first leaves in about a week or two.

When plants are about 2 inches tall and have one or two more sets of leaves, use scissors to clip greens and enjoy.

Do you have an indoor gardening project that keeps you busy in winter? Please share your ideas here!

By Jodi Torpey
Denver master gardener