March 29, 2024
BANGOR DAILY NEWS (BANGOR, MAINE

Overwintering herbs takes special care

Unlike decorative houseplants, indoor herbs work hard for us. Since we may be harvesting regularly for culinary purposes, these delectable plants need special attention.

Whether you’ve brought herbs in from the summer garden, or started them from seed or cutting, if you plan to enjoy them all winter you’ll need to consider many growth factors.

When we grow plants inside, we create for them a relatively controlled environment. Indoor plants aren’t subjected to the diversity of nature. There’s no rain, no harsh wind, no penetrating sun. Since the environment is so modified from the outdoors, special consideration must be given to moisture, temperature, air circulation, light and fertility.

Each factor has the potential to limit the success of an individual plant. Therefore, it’s impossible to say to which factor we should pay more attention. One gardener may put more emphasis on fertilizing plants regularly, but if light is in short supply, the plant’s growth will still be limited.

Another gardener might religiously rotate plants from windowsill to a lighted plant stand, but if the ambient temperatures have remained below a critical threshold, growth will be affected. Although it’s impossible to say which factor is most critical for indoor cultivation, most people would likely say that light is a primary consideration.

Light, indeed, is critical. All plants are autotrophic, that is, they make their own food. To make their own food, they require light. Most indoor herbs need about five hours of direct sunlight each day. Some specimens, such as mint, bay, parsley, thyme and rosemary, perform well with less light.

If natural, direct sunlight is not available, a two-tube fluorescent lighting system may be used. These cool lights may be placed at close range, 6 to 8 inches above the herbs, and should be run for 14 to 16 hours each day.

With limited space and light, maintaining adequate spacing between plants is vital. Be sure that air movement can take place, or else you’ll probably notice an increase in pest problems, both with insects and disease. A good general rule to observe: Don’t let the foliage of one plant touch the foliage of another.

If possible, on warm winter days, crack the windows in adjoining rooms to promote air flow around the indoor herbs. Be sure not to let cold winter air blast the relatively tender herbs. Although most herbs like temperatures on the cool side — about 65 degrees F — they certainly don’t appreciate a blast of frigid Maine winter air.

A balance of ideal light and temperature would not be complete without balanced applications of fertilizer. Keeping indoor herbs productive can be tricky during the winter. The object is to be certain to feed the plant enough to promote growth, yet not to oversupply nutrients in such a way that the plant can’t keep up with the food supply.

Be sure not to overfeed your potted herbs. Too many nutrients without adequate light and warmth will result in leggy plants. Fertilize once a month with applications of seaweed or fish emulsion, according to label recommendations.

The greatest effort in propagating indoor herbs will come from routine care and watering. Don’t overdo it. Overwatering is probably the No. 1 killer of indoor potted plants. Another good general rule: Don’t waterlog the potting medium. Allow the root ball to dry a bit and then water it thoroughly. This doesn’t mean you should let the roots dry completely, just use your best judgment and try to avoid having the roots soaking wet all the time. Try to avoid shallow waterings; when you irrigate, completely wet the root zone.

Once your garden soil has been worked in spring, indoor potted herbs can be acclimated to the outdoors, and planted directly into the garden. Be sure to allow the plants slowly to become accustomed to the greater environment by setting them outside in a protected place for about a week before transplanting them into the garden soil. Gradual exposure to the bright sun and wind will ease their transition to outdoor living.

Diana George Chapin is the NEWS garden columnist. Send horticulture questions to Gardening Questions, RR1, Box 2120, Montville 04941, or e-mail to dianagc@ctel.net. Selected questions will be answered in future columns. Include name, address and telephone number.


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