RosemaryWinter is nearly here, and there's likely to be trouble in the herb patch. While it may be too early to see winter damage, you may have noticed that some herbs fail to thrive. And, each spring, you may expect some herbs to simply wither and die.
To avoid these problems, and to preserve the size, beauty and productivity of mature perennial herbs, we have to address poor drainage, cold snaps and sudden warm periods during winter.
Our clay soils and ample winter rains coupled with cold and sudden re-warming can mean a permanent early retirement for many herbs.
Whether fully hardy or not, perennial herbs will do much better if you work gravel, coarse sand and compost into the soil. Improve the drainage of your site, not just the planting hole. Work the amendments into the soil to a depth of at least 12 inches. If you have very heavy soil and/or standing water, consider planting elsewhere, planting in raised beds or using drain tiles to drain the site.
Less hardy herbs also need mulching to do their best year after year and to survive the occasional severe winter or a winter with sudden warming periods.
The mulch not only will help protect herbs from the cold, but also will keep the ground cool during unexpected warm periods. Warm weather can awaken a plant long enough to produce new growth that will be killed when the cold returns.
Another thing you can do to prevent damage to your herbs is to resist planting too late in the growing season. Allow at least six weeks for a plant to settle in before winter cold comes.
Also be careful with fertilizer: The overuse of nitrogen-rich fertilizer will produce herbs with tender growth more sensitive to cold and with less flavor and essential oils.
-- Homes & Gardens staff
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