Winterizing your herb garden isn’t difficult, but the actions you take will differ depending on the type of herbs you have planted. Just as with other plants and flowers, some are annual others perennials. That means they either die off with the cold weather or simply become dormant, to rise again the following spring.
Basil, for example, doesn’t do well in colder climates and will often not survive the winter. They can be grown indoors, or simply planted again next early spring. Sage and Thyme winter well on the other hand, though their leaves may wither and the stalks may appear dead. Try scraping the side of a sample and look for green material. That’s a sign that the plant is still alive and will blossom later in the season.
Most herbs require little or no fertilizer, since they do well in what would be considered poor soil for other plants. If you do fertilize, avoid adding any after early August. You don’t want to encourage a spurt of new growth that won’t have time to mature before winter sets in. That will leave the new growth vulnerable, making it hard to survive the snow or frost.
As growth slows, the plants prepare themselves for winter. Many lose their leaves. In some cases the stalks may actually harden and die. But, in the case of perennials, the roots are still alive even though dormant. As the snow clears and the ground warms, they’ll sprout again, rest assured.
A similar warning applies to pruning. Trimming back in August or September will stimulate new growth, those new shoots don’t have time to mature before winter, and often will not survive. That doesn’t help the herb’s chances the following spring, since that dead growth has to be cleared before new growth can takes its place.
Good drainage is important for almost all herbs, since most prefer slightly dryer soil. Peppermint prefers it slightly moister, but even there the key word is ‘moist’, not ‘wet’. Rosemary, Lavender, Thyme and others are Mediterranean natives so they’re used to rocky, dry soil and lots of hot sunshine. The coming of winter makes this point even more important.
Wet soil draws more heat out of the plant than dry. When it becomes cold enough, of course, it freezes. That can crack roots, cause frost heaving as the ground alternately freezes and thaws over winter, and other ill effects.
Adequate drainage is encouraged by the right mix of sandy loam and clay soil. The clay retains moisture that is later released to plants as the surrounding soil dries. Sandy loam provides lots of spaces for air to move around, while allowing excess water to pass through easily.
A good mulch will help the surface enormously. A mixture of pine bark and needles or a commercial mixture is great. Sawdust is helpful. In special cases, it can be helpful to build a small wire cage around the plant to help retain the mulch and (if lined with plastic) block excess cold wind.
Prepare for winter and you’ll find your herbs eager to sprout at the earliest opportunity in the spring.