McCreary: Protect tender herbs from frosts, freezes

We know that October spells the end for ripening tomatoes, cucumbers and other summer vegetables, but it’s easy to forget that some of our favorite herbs are also at the end of their warm-season productivity.

Many herbs are annuals and, like petunias and marigolds, they fade away this time of year and are gone after a severe cold snap. The only hope for more basil is to cut any remaining stems and hold them in a glass of water for a week or more. And although cilantro favors cool weather, it won’t hold up if the thermometer drops too low.

Oregano, thyme, and other woody-based herbs, however, are cold-hardy and need only a trim of lanky stems this time of year to stay tidy. But a few other perennial herbs are more cold-tender and need a little extra attention now that nights are colder.

Lemon verbena, for example, should not even be trimmed until new buds appear in spring. Its branch tips are often killed in winter, but lower stems simply go dormant. If you’ve planted it in the warmest microclimate on your property, it might escape cold damage altogether.

If you have aloe vera growing outdoors in a pot, it should be brought indoors on cold nights or you might find it turned to mush and beyond salvage if temperatures drop too low.

For gardeners determined to keep a pot of tender culinary herbs going, one solution is to plant in an easily moveable container such as a shallow flared dish with drainage holes, leave it in a convenient location outdoors during mild weather, and bring it inside when nighttime temperatures drop below 40°F. Sunshine and outdoor air lead to more robust flavors and stronger stems than when herbs are restricted to the kitchen counter.

Some gardeners are confused by parsley, thinking that it succumbs to cold, but that is rarely the case. Parsley is a biennial, which means that it produces leafy growth its first year in the ground, a tall stalk that flowers the second year, and then dies naturally. If seeds are allowed to form, numerous sprouts usually appear the following spring.

Protect lemon grass

If you’ve been growing lemon grass (Cymbopogon citratus), it will definitely need to be sheltered throughout the winter months. Our climate is mild enough that it may not be killed by a sudden frosty cold spell; it may simply die back to the ground and re-sprout in spring. But it can’t endure freezing.

Lemon grass, an essential ingredient in Thai and other Asian cuisines, brings a zesty flavor to a wide range of dishes, from chicken and lamb to soups and salads. In Southeast Asia, it is also used in teas to ease depression and fevers, as well as in a paste to relieve joint pain, headaches and digestive problems. Its oil has long been used in soaps and perfumes and of late is highly valued for aromatherapy.

In tropical climates, lemon grass can be planted in the ground where, in ideal conditions, it grows in slowly spreading thick clumps up to 6 feet tall. Our winters are too cold, however, for dependable year-round outdoor culture in garden beds.

Container culture

When grown in a 12-inch or larger container, lemon grass achieves about half the size of plants in the ground and is easily protected in winter by covering with a sheet or plastic suspended on a frame.

Hard frosts turn stems and leaves brown. If inner stems are undamaged, cut the clump about 4 inches from the ground or just above the soil level. By fall, it will regain nearly 3 feet in height.

Lemon grass relishes a hot spot outdoors in full sun, but it will tolerate a few hours a day in part shade. Like so many other tropical plants, success depends on ample moisture.

There are several options for getting started with lemon grass. Many nurseries sell plants, but it’s easy to grow and fast to develop from seed. It also sprouts from thickened lower stalks you buy from the produce counter at grocery stores, providing that part of the rhizome is still attached at the bottom. It is this lower stalk that carries the most intense flavor, though leaves are used in some recipes as well.

The inch-wide, light green leaves bear pale center stripes and form an attractive arching clump wherever lemon grass grows. Like other grasses, clumps can always be rejuvenated by shearing them off just above the ground.

Grassy relatives

Similar Cymbopogon species are less common in home gardening and are also tender enough to warrant winter protection. All have a greater value outside the kitchen than the more familiar lemon grass.

Citronella grass (C. nardus) is the source of oil used in perfumes and mosquito repellents.Ginger grass (C. martinii) and Indian lemon grass (C. flexuosus) are used medicinally and in cosmetics.

Rosemary McCreary, a Sonoma County gardener, gardening teacher and author, writes the weekly Homegrown column for The Press Democrat. Write to her at P.O. Box 910, Santa Rosa, 95402; or send fax to 664-9476.