Continue to order seed, bulb, and nursery catalogs to assist in planning your garden for the upcoming year. To help you choose the best plants for your garden, take advantage of the resources of the Chicago Botanic Garden's Best Plants Web site, the Plant Information Service, Lenhardt Library, or the Joseph Regenstein, Jr. School of the Chicago Botanic Garden.
Unseasonably warm and dry winter weather will further stress plants that were not watered adequately during a dry Chicago autumn. During periods of winter thaw, water evergreens, broadleaved evergreens, and conifers as needed. Water newly planted trees and shrubs and all plants, including turf, that might be in the path of salt spray from salted roads.
Continue to check plants for signs of damage from weather or animals.
If necessary, continue to use potassium- or calcium-based de-icing products on walkways rather than sodium-based products. If possible, consider using sand on slippery surfaces. Always shovel snow before applying any product.
Unusually mild weather might cause some buds on flowering shrubs to bloom prematurely. These flower buds will not rebloom in spring, but there will be enough of the unopened buds to flower at their appropriate time. Forsythia, viburnum, flowering quince, weigela, and magnolia will often bloom sporadically during warm periods in late fall or early winter.
Continue to cut branches for forcing indoors. Branches with interesting foliage as well as flowering branches can be forced. Prune carefully, using proper pruning techniques and cutting off only those branches that are not essential to the plant’s basic shape. Branches should be at least 1 foot long, full of fat flower buds, and cut on a day above freezing. Lay the branches in a bathtub filled with room-temperature water. Make crosscuts in stem ends or smash woody ends with a hammer to allow quick uptake of water. Keep branches in a cool room out of direct sunlight and change the water every other day. When the buds color up or the foliage begins to unfurl, arrange the branches in a vase and display them in a cool room out of direct sunlight.
Good choices for forcing this month include serviceberry (Amelanchier), magnolia (Magnolia), flowering quince (Chaenomeles), forsythia (Forsythia), crabapple or apple (Malus), flowering pear (Pyrus), flowering cherry (Prunus), honeysuckle (Lonicera), spring-flowering witch hazel (Hamamelis vernalis), and redbud (Cercis).
Heavy pruning of large woody plants can be done this month, weather permitting. To avoid sacrificing spring flower display, prune large flowering trees and shrubs after they bloom in spring. Fruit trees are best pruned in late February or early March.
If tree branches become covered with ice, let the ice melt gradually rather than cracking the ice with a heavy object. If large evergreen branches become anchored to the snow, gently sweep snow with a soft broom and then elevate the branch from underneath. Using heavy or sharp objects like shovels to remove snow on trees risks cutting the tree bark and creating a point of entry for disease or insects.
Check newly planted softwood trees for frost cracks or sunscald injury that might occur when winter temperatures fluctuate dramatically from a sunny warm day to a subzero night. Consider wrapping vulnerable tree trunks with protective wrap in fall and removing it in early spring.
If weather is unusually warm, avoid pruning trees that will "bleed," or discharge large amounts of water, such as elms, maples and birches. Prune these trees only when weather is quite cold or in summer.
Immediately prune out broken or damaged branches.
To keep cut flowers fresh, place them in room-temperature water as soon as possible. With a sharp knife or pruners, make an angled cut and remove 1 inch from each stem. Make this cut while the stem is under water. Cutting on an angle increases the surface area for water intake. Add floral preservative to the vase water. Most preservatives contains an acid (to neutralize alkaline tap water) and an ingredient to discourage bacteria. Remove all foliage below water level. Cut flowers prefer a cool, humid environment and should be kept out of bright light and away from heating vents. Mist the air around the arrangement and change the water daily. 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, as can cigarette smoke.
If healthy cut roses suddenly develop drooping heads, it may be due to air bubbles trapped in their stems. Float the entire stem in a sink full of warm water. Trim another inch from the stem, cutting on an angle below water level. Try to gently straighten the drooping flower head as the flower and stem continue to float and the cut end of the stem remains under water for at least one-half hour. When the flower head hardens to a straightened position, the roses may be placed back in the vase.
Continue to care for amaryllis following their flower display. Allow all stems to wither before cutting them off the bulb. Keep the pot in a bright, warm location, out of direct sun. Water the plant as needed. The green, strappy leaves will continue to grow. When all danger of frost has past, take the pot outside to the garden and keep it in a location protected from afternoon sun. Fertilize the bulb every 10 to 14 days with a liquid 10-10-10 or 15-15-15 mix. This fertilizer helps refuel the bulb for another season’s flower show.
In February many houseplants might show signs of stress caused by light deprivation, overwatering, insufficient humidity, and overheated indoor air. Stressed plants are more likely to develop insect and disease problems, so monitor your plants for early signs of trouble. New houseplants or gift plants may also harbor pests, and these plants should be isolated before joining other plants in your indoor garden. Pests to look out for include the following:
- Spider mites — Look for webbing in leaf axils, stippled foliage and weak, off-color leaves. Mites are often difficult to see without a lens.
- Scale — Characteristic sticky, clear honeydew is produced on leaves by these small, immobile, rounded insects usually found on stems and veins of leaves.
- Mealybugs — Easy to spot, these insects resemble crowds of tiny cotton puffs.
- Whitefly — Whiteflies are a major problem in many greenhouses because they can quickly move to neighboring plants. Look for tiny, white, mothlike insects often found on the undersides of leaves.
- Fungus gnats — The adult black gnats fly around the plant but do no damage. The immature larvae in the moist soil can chew plant roots. They are often a problem in overwatered plants or overly moist flats of seedlings.
If winter sunlight has been minimal, foliage plants as well as herbs and all flowering plants might require artificial light to supplement the diminished natural sunlight. A light table would require two 40-watt fluorescent tubes, one cool and one warm, for every foot of shelf space filled with plants. Group plants with similar heights together so the fixtures can be placed just a few inches above the plants. Keep the lights on between 14 and 16 hours a day.
Continue to start seeds for spring- or summer-blooming annuals, vegetables, and perennials. Follow the directions on individual packets as to which types of seeds require bottom heat, light, or darkness to germinate. Some seeds might require a short period of chilling before being sown.
Sow seeds in fiber pots or trays using a premoistened soilless or seed-starting mix. Sow large seeds in slightly indented rows and cover them lightly with a thin layer of the mix. Finer seeds may be broadcast directly on top of the soil. Some types of seeds will require a glass or plastic cover to provide supplemental humidity. Water seeds from the bottom, or use a fine mister to keep the soil moist. To germinate, most seeds require a warm, bright location out of direct sun. Ventilate covered seeds daily, especially in bright conditions.
When germination occurs, gradually increase light levels. When two sets of true leaves develop, transplant small seedlings to a larger fiber pot that contains a slightly coarser "growing-on" mix. Continue to water from the bottom to encourage strong root development. Begin fertilizing with a quarter-strength 10-10-10 solution. As the plant grows larger, switch to a half-strength solution once a week.
Approximately seven to 10 days before setting out plants, harden them off by taking them outside for a few hours a day and back in again at night. Gradually increase the time spent outside until the plants are ready to be planted in containers, window boxes or directly into the garden.
Talk around the Garden is all about orchids this month, with our first-ever Orchid Show opening on February 15. Among the many interesting orchid conversations, there is one question that gets asked repeatedly by gardeners of all skill levels: "How do I repot my orchid?"
Luckily, the answer for most orchids is, "It's easy."
Orchids should be repotted when new; every year or two; or when crowded roots push up and out of the pot.
Spring: time for a close-up.
Other than watering and occasionally fertilizing them, you probably don't look closely at your orchids all that often when they're not in bloom. Spring is the time to examine each plant with a critical eye to assess the need for repotting. It's also when you'll see the new growth that signals emergence from the dormant cycle—the best time for repotting.
Is it new? Holiday gift orchids or newly-purchased plants are often planted with sphagnum moss, which absorbs and holds water—creating prime conditions for orchid root rot. Repot all new orchids as soon as they're done blooming.
When was the last re-potting? Orchids need both the nutrients from the chunky, loose bark mix they're planted in and the air space in between the pieces. As the mix breaks down to particle size, it compacts the air spaces inside the pot—virtually suffocating your orchid's roots. Check the bark mix every spring and repot when you notice decomposition.
Is it crowded in there? While orchids prefer a small pot—weaving their roots through the compost as they grow—they eventually run out of room. That's when their roots push the plant up above the rim of the pot or reach out into the air, looking for breathing space—a sure sign that it's time to re-pot.
Fresh bark mix is chunky and loose; decomposed mix fills in the air pockets that orchid roots need.
Gather a few supplies.
Repotting an orchid sounds complicated and exotic, but it's a simple process requiring just a few items:
- Fresh bark mix. The mix matters: some typical store-bought mixes deteriorate far too rapidly. For high-quality mixes, Chicago-area orchid fans can travel west to Orchids by Hausermann's, an orchid nursery that carries several bark options—not to mention fantastic plants. Online orchid specialists offer more options, too.
- A pot that's one size larger than the original, in case your orchid is ready to move up.
- Pruners and/or a sharp pruning knife, sterilized in a 10 percent bleach solution.
- Scissors or a razor blade for trimming roots and leaves.
- Gloves to protect your hands from splinters and prickles.
- A thin dowel or blunt knife for settling compost around the roots.
Healthy orchid roots are white; pale green tips indicate new growth.
Get to the root of it.
Now comes the interesting part.
Remove the orchid from the pot. Roots can be potbound and sticky; first try "massaging" the pot to loosen the rootball. Not budging? Work a dull knife down and around the inside of the pot, then invert it and tap the pot on your work surface to remove.
Soak the roots. Examine the rootball and feel a few root ends. If the rootball is stiff and dry, soak it in water for a few minutes to soften the tissues. Careful: dried-out roots can snap!
Loosen and untangle roots gently. As you do, trim away black/hollow/soggy roots and remove the old compost trapped between the roots. Refresh the disentangled roots with a thorough rinse to wash away all the tiny bits of soil that can clog up breathing spaces inside the pot.
Settle plant into the new pot. Holding the plant in one hand, place the plant down into the pot. Pour fresh bark mix around the plant, using a dowel or blunt knife to work it all the way down and between the freshly separated roots.
Water thoroughly. Then test your patience: wait a full week or two before watering again—that break stimulates root growth in the new medium.
Know your orchid.
While this basic potting method works for most orchids, some require special care, such as dividing or mounting. Our Lenhardt Library is a great resource for specialty orchid information—we've counted more than 600 books, videos, and other orchid resources there, all available to smart gardeners in one beautiful space! Come in for a visit while you're at the Orchid Show!