Warm winter can cause plants to bloom early

Recent warm weather has resulted in some plants, such as iris, showing some green growth, with some buds swelling on trees and shrubs. Extended periods of warm weather in midwinter can be problematic for some plants, but there is no special maintenance for garden beds in response to warmer winter weather.

Evergreens growing in containers benefit from watering during warm and dry periods, providing the container soil is not frozen.

Warm days provide an opportunity to do some pruning.

• Moth orchid, or Phalaenopsis, will bloom for months during the winter. Continue to provide bright light and keep it out of direct sun in a warm room.

During the winter, try to provide extra humidity from pebble trays or humidifiers, or move the plant into a bright bathroom where humidity is high from daily showers. Flowers and developing buds will drop if the plant is moved to a cold room or exposed to drafts.

After flowering, allow the stem to yellow before cutting it off at the base of the plant. Now begin to fertilize the plant twice a month with a dilute orchid fertilizer. Wash the foliage monthly. It's not necessary to take this plant outdoors for the summer because it prefers indoor conditions.

Continue normal watering and fertilizing until a new stem appears, about 10 to 12 months later. When the plant initiates flower buds, discontinue fertilizing.

• Monitor houseplants for insect problems that often occur when plants become stressed. New houseplants or gift plants can also harbor pests. Isolate these plants before adding them to your collection.

Some common pests to look out for include:

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, moth-like 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.

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