Winter Gardening Tips From A Master Gardener For Colorado Green Thumbs

Listen Now
Photo: Master Gardener Winter Garden
A blue spruce covered by snow in master gardener Loni Gaudet's garden.

It doesn't seem obvious to think about your garden when inches of snow cover the ground and the temperatures brush into the single digits.

But winter is a vital time to be planning for greener harvests, said Loni Gaudet of Berthoud. Gaudet is a CSU Extension Master Gardener, and she talked to Colorado Matters about the best winter gardening strategies. She answered CPR listener and reader questions.

Paul Skold, Arvada: "Is there a minimum size for a successful plot of sweet corn?"

Corn is one of those plants that needs space to grow and pollinate. Because corn is pollinated by wind, Gaudet recommends planting in blocks rather than a single long row. She says a 4-foot by 4-foot block is about the smallest area that will work.

Johnathan Toth, Centennial, via Instagram: "When is the best time of year to apply compost to your garden?"

Before laying down compost, Gaudet highly recommends doing a soil test. That way you know exactly the vitamins your garden needs. Vegetables, annuals and some perennials prefer a soil that's 4-5 percent organic matter, while native plants and cacti are better adapted to soil with just 1-3 percent organic matter. Colorado State University will perform one for you.

Compost can be put down anytime, but Gaudet prefers applying it in the fall. That gives the compost time to age and break down before plants are introduced. Gaudet also encourages gardeners to use compost as a mulch and not turn it all into the soil.

Photo: Master Gardener Winter Garden | Vegetable Beds
Master gardener Loni Gaudet's raised vegetable beds during winter.

Sarah Martin, Centennial: "Why did my cherry tomatoes fail miserably last summer?"

There's a lot that could have happened. Gaudet recommends sourcing where your compost is from and running a soil test. Commercially available composts can be high in salts, but lacking in the right kind of nutrition. Compost made with hay and straw may contain herbicide.

It's also possible too much compost was applied over the years, leading to a soil too rich in organic matter. Similarly, turning compost into the soil instead of using it as mulch can damage soil structure and the bacteria, worms and other microbes needed for healthy plants.

Carolyn Weber​, Aurora: "Is it too late to plant garlic for next summer?"

Yes, it's too late. October and November are the months to plant garlic for the for the best results the following summer, when the length of daylight and soil temperature are in ideal conditions.
However, Gaudet says experimenting by planting now might result in a crop, although the bulbs may be smaller than usual.

CPR News Reporter Ann Marie Awad: "What's the best winter cover crop for a fruit/veggie patch?"

Cover crops are also known as green manures. They're plants that provide protection and nutrients for the soil between grow periods.

Gaudet again recommends performing a soil test so a gardener knows what's lacking before adding any new nutrients. It's also important to know your goals before selecting the ideal cover crop. Also, make sure you use an annual as a cover crop, so it doesn't come back unwanted later.

Looking to prevent the soil from drying out and eroding in the wind? Plant grasses such as rye and wheat. Want to introduce nitrogen to the soil? Legumes are the way to go, try beans and vetch. And if you're trying to break up the soil, turn to root crops such as turnips and radishes.

Come spring after you cut the cover crop down, allow time before planting so the roots can decompose. And if you have unused beds in the summer, grow buckwheat to suppress weeds and attract lots of pollinators.

Photo: Master Gardener Winter Garden | Grass
Green needle grass covered in frost in master gardener Loni Gaudet's garden.

Austin Ouellette‏, Denver, via Twitter: "If I wanted to grow a pepper that originates from Central America called chilhuacle negro, is it possible to do so sustainably in Colorado?"

Many vegetables gardeners grow are not endemic to North America, and peppers are great example, Gaudet said. It's as sustainable as any other pepper grown in a garden, so plant on.

When's a good time to prune xeric plants — ones that thrive in arid climates — such as penstemons, yarrow and Russian sage?

Leave the pruning 'til spring. During winter these plants can provide shelter for new growth, insects and other animals, as well as offering food for birds.

Is it important to water in the winter time? What are the best practices?

If a month goes by without any snow cover, then you need to water your plants and trees. Make sure the temperatures are above freezing and the soil isn't frozen first.

Water around the base of the plant and within the dripline, the farthest-reaching branches. Water midday so that the water can soak into the ground before chilly nighttime temperatures.

New plants are especially vulnerable to winter drought injuries, so pay them and your less drought-tolerant perennials extra attention.

Trying to figure out how much to water a tree? The rule of thumb is 10 gallons per inch of diameter. Meanwhile, shrubs generally require 5 gallons twice a month. Shrubs less than 3 feet tall should receive just 5 gallons a month, and those taller than 6 feet need 18 gallons monthly.