Creeping Thyme

In spring, lift the whole root ball of an established plant and pull or cut it into smaller parts, making sure every piece keeps rootlets attached. Replant the divisions 8 to 12 inches apart in gritty, well drained soil and water them in. Thyme is slow and erratic from seed and can take years to fill in, but division carries mature roots and true-to-type growth, so it re-establishes fast. It is also the cheapest way to renew a patch that has gone woody, using the young outer growth and discarding the old center.

As new growth starts in spring, shear the mat back hard, cutting into the older stems but leaving some green shoots on each one. Do this every few years, or yearly on patches that have gone bare and twiggy in the middle. Creeping thyme is a sub-shrub: its stems lignify with age, and old wood carries few leaves, so an unpruned mat thins to bare wood at the center while it creeps outward. Cutting back forces fresh leafy growth from the base before the plant has to be replaced.

Through hot, humid stretches, check the mat for patches that brown and collapse from the center. Shear the affected plants back rather than pulling them: melted-out thyme usually recovers from a hard cutback. Only dig out a plant whose crown has actually rotted through, and fix the drainage before replanting that spot by working in coarse grit or raising the bed. Separately, in hot, DRY stretches look on the undersides of leaves for the fine stippling and webbing of spider mites, and knock them back with a hose spray and by relieving drought stress. Thyme evolved on thin, rocky, dry ground and has no tolerance for wet feet, so warm wet soil invites root rot and the mat melts out from the center; Iowa State reports that cutting plants back helps them recover, so a collapse is not automatically a death sentence, and only a crown that has truly rotted needs replacing. Spider mites run the opposite way, building up on plants already stressed by hot, dry weather rather than humid weather.

When the flower buds have formed but before they open, cut the leafy stem tips on a dry morning, before midday heat. Hang the cuttings in small bunches in a dark, warm, well ventilated place to dry. The essential oils that carry thyme's flavor peak in the leaves just before bloom, then drop as the plant shifts its energy into flowering and seed. Cutting on a dry morning after the dew has burned off but before the day's heat means the oils are still in the leaf and the foliage is dry enough not to mold as it dries.