Southernwood is a woody perennial herb that is hardy through USDA Zone 4. This plant does not come reliably true from seed; most of its seeds are infertile. The best way to cultivate southernwood is by root division. Find small starter plants from nurseries specializing in herbs. Its foliage has a slight lemony fragrance, and it is used in sachets to repel moths and other insects from clothing and linens. In ancient times, clean laundry was draped over southernwood to absorb its fresh, clean insect-repelling scent while drying.
Pick a spot in full sun. Southernwood will grow in soil that is dry and poor.
When preparing the planting site, it is not necessary to improve the soil with soil amendments. Turn over the soil with a shovel to loosen it, and then rake the area smooth.
Dig a hole that is slightly larger than the transplant's root ball. Insert the roots into the hole and back fill with soil. Firm the surface of the soil gently, but firmly.
Water the newly transplanted southernwood with a watering can. Water weekly until the plant is adjusted to its new home and showing new growth. Thereafter, the plant will grow without additional watering. Natural rainfall is sufficient for them, except in times of extreme drought.
Cultivate to control weeds or apply a thin layer of organic mulch. Southernwood like hot, dry soil conditions. If you do apply mulch, put down only a 1-inch layer of straw or hay for weed control.
Side dress with finished compost in early spring. Pull back mulch (if any) and spread 1/2 inch of compost around the base of the plant. Replace mulch. Southernwood does not need any additional fertilizer.
Wait until the plant begins to grow in early spring before pruning, then remove any dead or diseased wood. Cut southernwood back by half when it is 3 years old to maintain its shape and size, if desired.