Germination temperature
Needs warmth: nothing below 10 °C (50 °F); best with days around 30 °C (86 °F) and nights around 15 °C (59 °F).
Visit deodar-seeds.in Herb growing guide
Great mullein is a biennial that makes a silver-woolly rosette in its first year and a tall yellow flower spike in its second. Sow the tiny seed on the surface in warm conditions and grow it in sun on poor, free-draining soil.
Needs warmth: nothing below 10 °C (50 °F); best with days around 30 °C (86 °F) and nights around 15 °C (59 °F).
Surface; cover no more than 0.5 cm (1/5 in).
About 7-10 days on bare, moist soil.
Needs light to germinate well; full sun for plants.
None needed.
Either; transplant while plants are small.
The seed is dust-fine (0.4-0.8 mm). Mix it with a little dry sand so it spreads thinly.
Not needed.
Not needed for sowing. Winter chilling of seed lying on the soil lowers the temperature it needs, which is why self-sown seed comes up early in spring, but sown seed germinates well without it.
Not needed. Soaking such small seed makes it clump and harder to sow.
Fresh seed germinated 0% at 15/6 °C (59/43 °F), 8% at 20/10 °C (68/50 °F), 97% at 30/15 °C (86/59 °F) and 95% at 35/20 °C (95/68 °F). Sow in late spring or summer outdoors, or indoors in warmth.
Press the seed onto the surface and, at most, dust it with fine soil or sand. Germination falls with depth and stops at 4 cm (1.5 in).
Gritty, free-draining seed mix or open, bare soil; avoid sowing into grass or thick vegetation, where emergence is much slower.
Keep the surface moist with a fine spray or by watering from below; do not wash the seed in.
Light matters: in one test 93% germinated in light against 35% in darkness. Do not cover trays with anything opaque.
About 7-10 days on bare, moist soil; under a grass cover emergence can take a month.
Prick seedlings out into small pots at two or three true leaves and plant them out when the rosette is still small; mullein makes a deep taproot and resents being moved later. Plant after frost in cold climates.
The plant forms a flat, woolly rosette. Rosettes need to reach a good size before winter to flower: in one study none under 9 cm (3.5 in) across flowered, and all over 41 cm (16 in) did.
A single spike rises and flowers from early summer to autumn; after setting seed the plant dies. In warm climates without winter cold, some plants flower in their first year.
Cause: seed covered too deeply or sown in cold soil. Fix: sow on the surface in warm weather and keep it in the light.
Cause: mullein moth caterpillars feeding on the rosette and spike. Fix: pick them off by hand; tolerate a few if you want the moths.
Cause: powdery mildew, usually on dry, stressed plants. Fix: give an open, airy site and remove badly affected leaves.
Cause: wet, heavy soil. Fix: grow on sandy or gravelly, free-draining ground.
Cause: a single plant can shed 100,000 or more seeds that stay viable in the soil for decades. Fix: cut spikes after flowering unless you want seed.
Sandy, stony or chalky ground in full sun suits it best; do not feed. Water a new plant once to settle it, then only in long droughts.
Because each plant flowers once in its second year, sow two years running to have spikes each summer, or let a few plants self-sow.
Great mullein is native to the Himalaya and suits hill gardens best. On hot plains choose a sunny, well-drained spot and expect a shorter life.
Garden verbascums with white, pink or purple flowers are other species and hybrids; their seed is sown in the same way, on the surface in warmth.
Sow mullein on the surface in a sunny, well-drained spot for tall yellow spikes next summer.
Great mullein is a biennial: it makes a rosette in year one and flowers in year two. Large rosettes flower reliably; small ones may wait another year.
No, or only very lightly. The seed needs light to germinate well and fails when buried a few centimetres deep.
On bare, disturbed ground it can, because each plant sheds huge numbers of long-lived seeds. Cutting the spikes after flowering prevents it.