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Windowsill herb growing

With the right care, some herbs can thrive indoors all winter.

By Lynn HuntCorrespondent of The Christian Science Monitor / October 16, 2008



It's a chilly fall afternoon. The garden has been put to bed in anticipation of the winter to come. Still, I am not quite ready to say goodbye to summer.

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I think about preparing a tasty tart with the last of our home-grown tomatoes, but the recipe calls for lots of fresh basil. No problem. Thanks to the bush basil growing in my windowsill herb garden, the pleasures of warmer days are still within reach.

As a rule, those who live outside warm winter climates bid farewell to their herb gardens when the calendar turns to October. Tender perennials like bay and rosemary can’t survive cold winters, and tropical-born basil will turn black at the first hard freeze.

Fortunately, the coming of autumn doesn’t have to mean giving up our favorite herbs. With adequate light, the right temperatures, and judicious watering and fertilizing, you can have savory sage stuffing at Thanksgiving, fresh rosemary with your holiday lamb – even tasty thyme for a St. Paddy’s Day stew.

All it takes is planning, preparation, and the right selection of herbs.

“Some herbs do well indoors and others don’t,” advises Gene Gage of Papa Geno’s Herb Farm in Martell, Neb. “A few good choices include rosemary, parsley, bay leaf, thyme, chives, oregano, dwarf sage, and mint.

"Surprisingly," he adds, "basil doesn’t always thrive because like me, it loves sun and heat, which can be hard to provide in the dead of winter.”

Barb Pierson, nursery manager at White Flower Farm in Litchfield, Conn., agrees basil can be a bad choice, particularly for beginners.

“People tend to water basils too much and let their feet get wet, which almost always results in a total plant meltdown," she says. "You might do better rooting cuttings in a bottle on a windowsill.”

No matter which herbs you choose – including the apparently fractious basils – location is the key to success.

For strong, vigorous growth, herbs need at least five or six hours of direct sunlight a day from a window with southern exposure.

If you don’t have the proper amount of sunlight, artificial lighting such as full-spectrum grow lights will help. Since fluorescent lighting is low in intensity, you’ll need to keep plants fairly close – no farther than 8 inches away from the tubes. A constant temperature of 68 degrees F. is ideal.

Most gardeners have heard the tale that herbs thrive in poor soil. This is definitely not the case indoors.

Whether grown in a window box or individual clay pots, herbs require excellent drainage. A high quality compost-based mix is fine, but some experts think it is wise to add a bit of perlite to ensure the good drainage that comes with a lighter soil.

Papa Geno’s recipe is one part potting soil, one part sand, and one part humus (compost, peat, leaf mold, etc.).

Feed your herbs once a month with fish emulsion at half-strength. Most important, beware of having too heavy a hand with the watering can or you might just kill your plants with kindness. Provide a drink only when the soil is dry to the touch, and never use cold water.

In addition, mist occasionally or set plants on a tray of pebbles filled with water to help them thrive in the often-dry indoor environment.

Ms. Pierson also suggests giving herbs a haircut regularly. “Prune herbs lightly and often to keep them bushy and healthy. And turn them from time to time to ensure even growth.”

She also recommends purchasing greenhouse-grown plants for indoor gardens. “Plants raised in the greenhouse are already acclimated to lower light conditions and are free from pests.”

If you move herbs inside from the garden you may unwittingly bring in unwelcome hitchhikers. Inspect plants with a keen eye and take action at the first sign of whiteflies, aphids, scale insects, or spider mites.

If your pots can be easily moved, dip the foliage into a bucket of warm, soapy water. Be sure to cover the pot with your hand or plastic wrap to keep the soil from falling out.

If soapy water baths haven’t done the trick after a couple of weeks, an organic spray or insecticidal soap should finish the job.

When spring arrives, you can move your portable herbs outside, or continue to cultivate your windowsill garden.

If plants remain indoors, remember they will dry out faster in warm weather and will want additional misting to increase humidity on the hottest days. At this stage, if your basils have defied the odds and survived, they’ll be past their best and will need to be replaced.

Indoors or out, make sure your plants are healthy and vigorous so you can continue to enjoy all the pleasures of the herb garden when winter winds blow again next year.

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