Gardening in Winter: Dos and Don’ts

Welcome to winter, one of the best seasons for gardeners. You have time to plan, prune, and enjoy those houseplants that don’t get much love during the outdoor growing season. Make the most of your winter gardening with these dos and don’ts from Chicago Botanic Garden experts.

DO prune your deciduous trees. From mid-November to mid-March, it’s much easier to prune because you’ll be able to better see a tree’s branching structure and there is less chance of transmitting diseases from one plant to another.

Winter is the perfect time to prune deciduous trees or remove nuisance buckthorn.
Winter is the perfect time to prune deciduous trees or remove nuisance buckthorn.

DON’T prune conifers. Needled evergreens can be pruned in late winter or early spring, before growth begins. Arborvitae should be pruned during spring and early summer.

DO water newly planted trees and shrubs that might be in the path of salt spray from salted roads during periods of winter thaw. Consider wrapping vulnerable trees to prevent damage from salt and extreme temperatures.

DON’T overwater houseplants. Because of shorter days and reduced humidity, most houseplants aren’t in an active growth phase, so they’ll require less water and fertilizer.

DO keep houseplants away from cold drafts, radiators, hot air vents, and cold windows. Plants growing in sunny east- or north-facing windows may benefit from being moved to a southern or western exposure for winter.

DON’T try to remove ice or snow that has frozen onto your outdoor plants. You might inadvertently damage them. Let it melt off on its own.

DO start to plan your garden for the new year. Order seeds and bulbs during the winter so you’ll be ready to plant in the spring. Need some help? Come to Super Seed Weekend on January 27 and 28 to talk to experts, attend a workshop, and find seeds and bulbs for your garden.

Ornithogalum 'Chesapeake Snowflake'
Ornithogalum ‘Chesapeake Snowflake’

Get more indoor and outdoor plant care tips with our monthly plant care checklists.

Plan for spring with a class in Front Yard Design, Backyard DesignGrowing Salads Indoors, or Small Space Food Gardens


©2018 Chicago Botanic Garden and my.chicagobotanic.org

Let it Snow

If you’ve been around Chicago in the past month, you’ve probably noticed the sort of weather we’ve been having.

Snow covers the grass of the Elizabeth Hubert Malott Japanese Garden in 2013. This protected grass can expect good growth in spring.
Snow covers the grass of the Elizabeth Hubert Malott Japanese Garden in 2013. This protected grass can expect good growth in spring.

You may even be bitterly cursing the snow and hoping winter will end, cheering this week’s thaw and higher temperatures. What you might not know is that all this snow has a number of benefits that will help your garden and landscape later this spring.

PHOTO: Closeup of bright red, raisiny eastern wahoo berries.
The fruit of eastern wahoo (Euonymous atropurpureus) creates a striking contrast against the snow.

Snow is a great insulator!

As winter presses on, the ground freezes deeper and deeper. This prolonged cold soil can damage roots over time. Snow helps create a blanket that reduces freezing of the soil. Warmer soil keeps microbes more active, which helps break down any plant waste that is in the soil, releasing nutrients. As a result of this insulation, your plants will have a much better start in spring!

Snow brings an important nutrient into the soil: nitrogen.

There are not many ways for nitrogen to enter the soil. While planting legumes and adding fertilizer are the most common ways we add nitrogen to soil, the weather provides nitrogen as well! Nitrogen is abundant in the atmosphere and is most easily collected by falling snow. As the snow melts, it deposits the nitrogen into the ground. (Apple trees and other plants benefit greatly from nitrogen deposited by snow.) When the ground is soft, plowing the snow into the soil will give the greatest benefit. Snow is sometimes called the poor man’s fertilizer.

PHOTO: Bare, yellow willow branches against a blue sky.
The yellow whips of this willow make an excellent contrast to the snow in most landscapes.

Don’t forget, snow is water!

When snow melts, it provides moisture for evergreen trees and shrubs. This moisture helps keep these plants happy and healthy throughout the winter. You won’t see damage right away, but a few years of snow-free winters can cause health problems in your trees.

Last but not least, snow can be very attractive in a landscape.

Snow makes plants with ornamental fruit, flowers, and bark stand out in the winter landscape. Plants like holly, ornamental grasses, euonymus, crabapples, roses, birches, ghost bramble, striped maple, dogwoods, willows, hazels, winter hazels, and witch hazels are only a few of many very attractive plants for a winter landscape. Dogwoods and willow varieties often will have young growth that is orange, yellow, or red. These same colors appear in the fruit of euonymus, crabapples, roses, and holly. Look for varieties that will complement your landscape.

If you find that snow is weighing down branches in your landscape and disfiguring the appearance of your shrubs or young trees, brush off the snow regularly and prune in the spring to remove any dead or broken branches.

PHOTO: Boxwood and hemlock trees against a fence in winter.
Evergreen trees and shrubs like boxwoods and hemlock need water through the winter to stay healthy.
PHOTO: Boxwood in winter; its branches weighted down with snow.
Boxwoods are prone to damage from heavy snows. Minimize damage by removing snow as soon as possible from the branches.

When the snow melts, check your trees and shrubs for damage near the trunk of the plant. Rodents, particularly voles, take advantage of winter snow cover and feed more aggressively on tender bark of young trees. If your lawn has developed paths of dead grass from these garden pests, rake affected areas of the lawn, apply a light application of fertilizer and seed the affected areas if damage is severe.

While many of us are hoping for an end to this winter, this abundance of snow is promising us a great spring!

©2014 Chicago Botanic Garden and my.chicagobotanic.org

How to Plant a Glass Jar Terrarium

Tim Pollak, outdoor floriculturist here at the Chicago Botanic Garden, recently taught a fun class, a glass jar terrarium workshop, with the Joseph Regenstein, Jr. School of the Chicago Botanic Garden. I went down to the production greenhouse that morning to learn how to plant a terrarium so I could share some tips with you. Follow the steps below to make your own! Need a little more direction? In the video below, we build a terrarium and give a few extra tips for success.

First, select a container such as a glass bottle, glass vase or bowl, miniature glass greenhouse, fish bowl, or something similar. Use a tightly closed, clear glass or plastic container to retain the most humidity. Open containers also work, but will require more frequent watering.

Let’s build the layers (from the bottom up):

1. Start with a layer of coarse sand or pebbles, usually no more than 2 inches deep.

2. Cut a sheet of landscape fabric or weed barrier to fit over the pebbles.

3. Add 1/4- to 1/2-inch activated charcoal (available at an aquarium store) to help filter the air and water and keep the terrarium fresh, especially if it’s a closed terrarium.

4. Use a clean, well-drained growing medium that is high in organic matter. A blend of peat moss, vermiculite, and perlite is a good choice. Soil should be slightly moistened prior to planting. If planting a desert garden, use the proper type of soil. Add about 2 inches of soil.

5. Select small plants that are suited to your light conditions. Add a mixture of plants with small or large leaves, short and tall in height, and other variations. Add color, either with foliage color and interest, or with flowering plants.

6. Add accents and ornaments to complete the look you are trying to create. Create a miniature landscape or theme.

Caring for your terrarium

Watering: Water until moistened after planting, being careful not to let water pool in the bottom where it cannot be removed. Leave the closed terrarium uncovered until the foliage has dried. A closed terrarium may not need to be watered for 4 to 6 months — look for condensation to form on the inside of the container to check the moisture level. Open terrariums need watering occasionally but not as frequently as other houseplants. Watering should be light to avoid standing water. 

Light: Keep out of direct sunlight as the terrarium could heat up too much and you could injure the plants.  Most plants suitable for terrariums prefer medium to low light. Bright, indirect sun is preferred. If you need to supplement light with an artificial light, a 100-watt bulb placed close to the terrarium or fluorescent lights placed directly over the terrarium will be helpful. Supplemental lighting should be provided 14 to16 hours per day.

Fertilizer: Generally, plants in a terrarium should not grow rapidly and should seldom need fertilizer. Do not fertilize more than one to two times per year. Use a slow-release pellet fertilizer at 14-14-14. 

Temperature: Keep terrariums in a warm location (65 to 70 degrees Fahrenheit). Avoid cold drafts as much as possible. Certain plants, such as desert plants and succulents, may prefer warmer temperatures.

Pruning: Many plants in a terrarium will gradually outgrow their limited space. Pruning will keep them in their space and often promote side-shoot growth that will help fill out the plants. Be sure to remove all trimmed vegetation from the terrarium when complete. As the plants mature, it may become necessary to remove certain plants or add others.

2013Feb11_9901Mark your calendar for 1 p.m. on Saturday, March 30, when Nancy Clifton, horticultural program specialist, will give demonstrations on terrariums in the Garden Shop. Visit the Shop online to see the selection of terrariums available for purchase as well!


©2013 Chicago Botanic Garden and my.chicagobotanic.org