University of Vermont Extension 
Department of Plant and Soil Science

Winter News Article
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PROPER WATERING AND OTHER DECEMBER GARDENING TIPS

 
Charlie Nardozzi, Horticulturist and
Leonard Perry, UVM Extension Horticulturist
 
 
Growing herbs indoors, proper watering of flowering potted plants, and watching for houseplant pests are some of the gardening activities for this month.

The outdoor gardening season may be over, but indoors you can grow many herbs. Sow seeds of parsley, oregano, sage, chives, and dwarf basil in clay pots. Once they germinate, place them under grow lights and water and fertilize (with a half-strength solution) only when very dry. You'll be rewarded with fresh herbs for your winter cooking.

Decrease water and fertilizer on Christmas cactus if the buds are developing. To prolong the colorful bracts (the showy parts on poinsettias), keep them where temperatures don't exceed 70 degrees (F) during the day or drop below 65 degrees at night. Keep potted amaryllis in a cool (60 degrees) shaded location until buds open. Then move it wherever you like. Cyclamen prefer cool temperatures, so keep them back from south-facing windows that heat up during the day.  Cyclamen also prefer even moisture, so don’t allow to wilt and definitely don’t keep too wet or they may rot.

African violets make great houseplants and will flower in winter if given supplemental light. To propagate new plants, take a leaf cutting, dip the cut end in a rooting hormone powder, available at many garden centers, and stick the cutting in a pot filled with vermiculite, perlite, or sand. Cover the pot with a perforated clear plastic bag and keep the soil moist. In a few weeks you'll have new plants.

If you brought in your geranium plants this fall and are growing them indoors this winter, chances are they've become very leggy by now. The cloudy, short days of November and December don't provide enough light for these plants to thrive. Cut back the plants to about one foot tall. They will resprout and grow bushier in the longer days of late winter.

If you've brought potted plants inside after a summer outdoors, chances are you're now seeing a shiny, sticky substance on the leaves and small black or green aphids on the undersides of the leaves. Sometimes a few dunks in a sink full of soapy water will control them, otherwise spray them with insecticidal soap or horticultural oil. Aphids are very prolific, so check and treat plants at least weekly (or according to label directions for spray products).

The warm, dry indoor air is prime breeding ground for spider mites on your houseplants. Look very closely at the undersides of leaves, at the base of stems, and on new buds for fine webbing. Set any suspicious-looking plants in the shower to wash off the mites, and repeat frequently. Or, if it's a small plant, treat as you would for aphids.     

Other garden-related activities for this month include buying gardening gifts for your favorite gardener for the holidays, keeping bird feeders full every day or two, treating your birds to high-energy suet or shelled peanuts (woodpeckers especially love these in wire-mesh feeders), using sand or “safe salt” products on icy walks to avoid damage to plants, and decorating with locally-grown and produced evergreen boughs, roping, and wreaths.

(Charlie Nardozzi is a nationally known horticulturist, author, gardening consultant, and garden coach; CharlieNardozzi.com). 

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