Come spring, what do you do with the perennial herbs in your garden? Check all of the woody perennials for new growth — mainly lavender, oregano, sage, tarragon, thyme, winter savory, and (if you’ve provided a bit extra protection in the central-Illinois hardiness zone) rosemary. Once the fear of hard frost is over, usually by mid-April, the time has come to prune the woody perennials that have survived the winter outdoors.
If you have regularly harvested during the previous growing season or pruned back dead wood last autumn, your woody perennial herbs may not need much pruning. If your woody herbs have been in the garden five years or longer, they may be too woody to salvage. It’s usual to replace woody perennial herbs after five years. Remember also that a few herbs are biennials and will produce flowers and seeds only in the second year. In other words, don’t trim your caraway plant that overwintered, because it will produce its seeds for harvesting in early July.
OK, back to spring pruning. Generally prune dead and scraggly growth on woody perennials, and clear out any debris or leaves around the bases of all plants.
Oregano requires pruning every spring to control plant spread. You may use a garden spade to sever roots around the plant (and these root divisions may be planted in another garden).
Lavender needs all-around trimming of at least one or two inches in the spring. If you didn’t remove flowers and dead stems in the fall, do it now, cutting back to where new growth has started.
Rosemary should not be trimmed until after it has flowered, after which it may be pruned severely. In warmer climates rosemary is grown as a year-round hedge. New rosemary plants are fairly easy to start from spring cuttings (roughly six to eight inches long, with the cut end trimmed of leaves and placed in sandy potting soil).
Sages require woody branches to be pruned. Some cultivars, such as tricolor sage, may be subject to severe die-back during the winter. Look for new growth — even wait until end of April — and prune back to those new spring leaves. Sages usually require spring shaping. Keeping flower buds trimmed off helps maintain a tighter-looking shrub. Also note that clary sage, a biennial, self-seeds after blooming in the second year.
Tarragon (use only French tarragon as a culinary herb) requires general spring pruning for shaping purposes. It only gets bigger and bigger every season, so consider dividing French tarragon by its roots in the early spring every three years, starting with “new” plants in your garden and sharing other root divisions with friends.
Thyme needs an early-spring pruning to remove dead woody sections, but wait until after the plant flowers to perform general light pruning — thyme doesn’t respond well to heavy pruning.
“Spring Wildflowers,” the latest program in the yearlong University of Illinois Extensive “Four Seasons” telenet series, will introduce you to the wonderful beauties found in our parks, forests, and back yards.
Identifying spring woodland wildflowers will be the focus of this program by Jennifer Fishburn, horticulture educator and Illinois Times columnist. Fishburn will also discuss some prairie wildflowers and offer tips on how to incorporate wildflowers into the home landscape.
“Spring Wildflowers” is offered at 1 p.m. Tuesday, April 19, and repeated at 7 p.m. Thursday, April 21.
In Springfield, the “Four Seasons” series is held at the U of I Extension Building on the Illinois State Fairgrounds. The telenet system allows live discussions between the instructors and gardeners throughout Illinois.
Please call 217-782-4617 to reserve a seat and information packet. Each session costs $2.