Propagation: seed, cuttings and division

01Seed: the cheap route

Seed is the cheapest way to build a herb garden and the best way to get named species. Use fresh seed where possible; carrot-family seed in particular loses viability quickly. RHS seed-sowing guidance is to sow into a clean, free-draining mix, label the tray, and keep the medium moist but not saturated (RHS).

Depth matters. Small seed is pressed onto the surface and barely covered; larger seed is covered to about twice its diameter. Water from below or with a fine rose so the seed is not displaced. Keep the tray warm and bright, but out of harsh midday sun.

02Pretreatment: cold, scarification and light

Some seed needs a signal before it will germinate. Dong quai and other umbellifers benefit from a cold, moist period. Astragalus and licorice have hard coats and germinate more evenly after scarification. Chamomile and codonopsis need light to germinate, so do not bury them.

03Cuttings

Cuttings preserve a named plant and are the standard route for rosemary, lavender, sage and thyme. RHS recommends semi-ripe cuttings of non-flowering shoots, inserted into a gritty mix with the lower leaves removed (RHS). Take 7–10 cm in late spring or late summer, cut just below a node, and keep at least one node below the surface.

Keep the humidity high but the compost not wet. A clear plastic bag over the pot works, as long as it is opened daily for air. Roots usually form in three to six weeks; tug gently to test. Pot on when the roots are 2–3 cm long, and overwinter the young plant under cover.

04Division

Division is for clump-forming perennials: mint, lemon balm, oregano, yarrow, motherwort, elecampane, peony and chrysanthemum. RHS lists division as a standard route for hardy herbs, with spring or post-flowering lifting (RHS). Lift the clump, split it with two forks or a sharp spade, and replant the vigorous outer pieces. Discard the woody or exhausted centre.

Peonies are the exception to the general rule: divide them in early autumn, replant with the buds only 3–5 cm below the surface, and expect a season or two of reduced flowering. Do not divide a peony in spring if you can avoid it.

05Runners, rhizomes and suckers

Mint, sweet violet and some grasses spread by runners. Lift a rooted runner with a slice of soil and pot it on; it is the easiest propagation in the garden. Ginger and turmeric are divided by breaking the rhizome into pieces with at least two buds each, then planting them just below the surface.

Goji and jujube can sucker. A sucker with roots can be severed and moved, but check that it is coming from the cultivar you want and not from the rootstock below a graft. For grafted trees, named cultivars are best bought as plants rather than propagated at home.

06Aftercare

New plants need less sun and more attention than established ones. Harden seedlings off over a week before planting out. Water cuttings and divisions consistently for the first season, and mulch to keep the root zone cool. Do not feed heavily; roots before leaves is the rule.

Label everything. A tray of unlabelled seedlings is a guessing game, and a herb garden is the wrong place for a guessing game. Record the species, the cultivar, the date and the parent plant.