February in the garden: Get outside to prune

Winter is a great time to research new plant ideas for your garden and learn about new gardening practices. But don't just stay indoors: The dormant season is also a good time to prune many trees and shrubs. Have a look around the garden every once in a while to monitor for animal damage so that you can take corrective action before a plant is ruined.

General garden care

Keep watering any evergreens that are planted in outside containers when temperatures are warm and conditions are dry. Evergreens continue to lose water through their leaves during winter and can suffer damage to foliage or even die if allowed to dry out. Watering during winter will generally improve the performance of evergreens growing in pots.

Check garden beds to be sure plants have not heaved out of the ground due to the freeze-thaw-freeze cycles that are typical in late February. Gently press the crowns of perennials back into the ground, but avoid compacting the soil by stomping heavily around plants. Applying a layer of mulch to insulate and even out the soil temperature will help prevent additional frost heaving.

If you have a fireplace, leave logs outdoors until you are ready to burn them, as insects can come in with the firewood. Never treat firewood with insecticides. Firewood can spread the devastating emerald ash borer, so do not transport any wood from ash trees outside of the emerald ash borer quarantine zone.

Consider using a freestanding plastic bin to compost in your garden. Check with your local extension office or local government to see if they have a program to sell these compost bins inexpensively.

Compost is the end product of composting, a process where organic matter is collected, mixed and allowed to decompose. In nature, deciduous leaves create a mulch layer that eventually decomposes. Like human-made compost, this natural recycling process returns nutrients to the soil and improves soil structure, and it is one reason why native plants growing in natural ecosystems usually do not need more fertilizer than nature provides.

In the garden, compost can be used to amend soil, or as a mulch layer on garden beds and around trees. Composting also reduces the amount of garden debris that ends up in landfills.

Even in winter, you can continue putting organic material from the kitchen in the composter. A bin keeps dogs and other animals out. Be sure only to add plant materials, such as fruit and vegetable trimmings; never put meat, bread, oils or pet waste in the compost.

Trees and shrubs

Winter is a good time to prune trees and shrubs. Heavy pruning of overgrown deciduous woody shrubs to rejuvenate them can be done in February and March. Start by removing all dead wood and prune old canes off at ground level, leaving only young canes. You also may need to cut back some of the young growth if it is spindly. If there are not any young canes, cut the large canes back to 2 to 3 feet from the ground. This will be unsightly at first, but if the plants are healthy, extensive new growth should start from the old canes in spring and fill in the plant.

Shrubs that formed flower buds last summer, such as lilacs and bigleaf hydrangeas, will not bloom in spring when pruned aggressively in the previous winter. Wait to prune them just after they flower in summer.

Continue cutting buckthorn out during the winter. There will be less impact on nearby plants, especially native perennials in natural areas, if this work is done when the ground is frozen. Be sure to treat the buckthorn stumps with an herbicide such as glyphosate or triclopyr herbicide to kill out the root system.

Glyphosate needs to be used at a high enough concentration to work as a stump treatment. Some recommend a 50 percent concentration, but Chicago Botanic Garden staff have had success with a lower concentration of around 30 percent. One of the drawbacks with glyphosate is that since it is water-based, it will freeze at below zero temperatures. It also will only work on the cut surface. Triclopyr is the preferred method because it is oil-based and will not freeze. It also is effective through the bark.

Annuals

It's not too soon to start seeds for annuals that get off to a slow start, such as pansies, violas, petunias, snapdragons and lobelia. While garden centers offer many favorites, the choices are seemingly endless when your grow your own annuals from seed. The quantity will be too if you save all the little seedlings.

Use grow lights to ensure success. A fluorescent fixture hung on a chain works best; the chain allows you to adjust the level link by link as the plants grow to keep the light at an optimum 8-12 inches above the seedlings. Providing bottom heat for the seeds until they germinate. Heat mats or cables can be purchased at your local garden center.

Thin seedlings as needed after the first set of leaves form to prevent overcrowding and keep the best plants. Remember to sow a few extras.

Indoor plants

As you carry cut flowers home, protect them from exposure to freezing temperatures. To keep the blooms fresh, place them in room-temperature water as soon as possible. With a sharp knife or pruners, make an angled cut — which creates more surface area for water intake — removing at least 1 inch from each stem. Ideally, make this cut while the stem is under water. Remove all foliage that would be below water level.

Add a floral preservative to the vase water. Most preservatives contain an acid to neutralize alkaline tap water and an ingredient to discourage bacteria. Cut flowers prefer a cool, humid environment and should be kept out of bright light and away from heating vents.

Do not place cut flowers close to a bowl of fruit or vegetables since the ethylene gas emitted by ripening fruit can damage the flowers. So can cigarette smoke.

ŸTim Johnson is director of horticulture at Chicago Botanic Garden, chicagobotanic.org.