Propagation: seed, cuttings, division and stratification

Most propagation failure is a mismatch between the seed's dormancy mechanism and what the grower did. Seed dormancy is not a defect — it is the plant's mechanism for not germinating in the wrong season, and it has to be satisfied deliberately.

The four dormancy mechanisms you will actually meet.

Cold-moist stratification. Many perennials from temperate climates require a period of cold, moist conditions before they will germinate. Echinacea, valerian, milk thistle and lavender all fall in this group. The practical method is either winter sowing outdoors, or refrigeration in moist media for a set period before sowing. Sowing these indoors in warm conditions in February and waiting is the classic failure.

Light requirement. Some small-seeded species need light to germinate — chamomile, lemon balm and many mints. Those are pressed into the surface rather than buried.

Scarification. Hard-coated seed needs the coat breached — physically nicked, or treated with hot water. This is what happens naturally in a bird's gut or a freeze-thaw cycle.

Double dormancy. Some species need warm followed by cold. Slower, and worth knowing rather than concluding the seed is dead.

Vegetative propagation is faster and clones exactly. A cutting or a division produces a plant genetically identical to the parent, which matters for two reasons: it preserves a plant that performs well for you, and it skips the dormancy and juvenile period entirely. Softwood cuttings in early summer root quickly in rosemary, lavender, sage, thyme and mint. Division is the fastest route for anything that spreads by runners or crowns — mint, lemon balm, valerian, yarrow, chives — and it is best done in early spring or autumn.

Which method for which plant.

| Plant | Best method | Difficulty | |---|---|---| | Mint, lemon balm | Division, or cuttings | Very easy | | Calendula, borage, basil, dill, fennel | Direct seed | Easy | | Chamomile | Surface-sown seed | Easy | | Rosemary, lavender | Cuttings | Moderate | | Thyme, oregano, sage | Cuttings or seed | Moderate | | Echinacea, valerian, milk thistle | Cold-stratified seed | Patient | | Garlic | Cloves | Easy | | Ginger, turmeric | Rhizome pieces | Easy, needs warmth | | Elderberry, hawthorn, rose | Cuttings or bare-root | Moderate | | Comfrey | Root cuttings or division | Easy, and invasive |

Hygiene in propagation matters more than in the garden. Damping-off in seedling trays is a fungal problem that a sterile medium, clean containers and good airflow prevent. Do not reuse soil from a failed tray, and water from below where possible.

Temperature governs timing, not the calendar. Germination and rooting rates respond to soil temperature, so a cold spring delays everything regardless of the date. A heat mat under seedlings is the cheapest large improvement available for someone starting plants indoors.

Harden off before transplanting. Plants raised indoors have thin cuticles and no wind resistance. A week of progressively longer outdoor exposure before transplanting is what prevents transplant shock.