Silphium mohrii

Germination

Sow in a cold frame in autumn. Can be sown directly in spring with prior cold stratification. In a cold frame, surface sow onto moist, well-drained seed compost. Just cover seed with a sprinkling of soil. Allow natural winter cold to offer ideal conditions for germination to occur in spring as the weather warms. For spring sowing, mix seed with damp soil and place in a zip-lock style freezer bag and cold stratify at 4°C, a fridge is ideal, for 6-8 weeks. The seeds can then be sown directly where spring warmth should offer germination in 2-3 weeks. Transplant seedlings when large enough to handle to final growing position, before the long tap root forms.

Growing

Prefers any ordinary, well-drained soil in full sun. Will tolerate poor soils. This plant may require staking. This plant may take several years to flower from seed. A tall, sturdy, rough plant on resinous stems. Split or broken stems will exude a gummy, bitter resin which was used by native Americans as chewing gum.

Cultivation

Propagate by seed. Deep tap roots make propagation by division difficult.