1/8"; darkness needed for best germination.
Recommended. Start 8-10 weeks before planting out. Sterile germinating mix with vermiculite is the preferred growing medium to prevent fungal problems. Keep at about 65-70°F.
Direct sow in mid to late summer in areas where hardy, zones 7-9.
PLACEMENT & CULTIVATION
A rare delphinium that entered the lexicon of horticultural discoveries in 1805 when collected and described by an eminent Swiss botanist of the era. It hails from the Mediterranean region and thrives in sunny areas and well-drained, even gravelly soils. It is a biennial that can be grown as an annual in areas where it is not hardy if started indoors early. After bloom, allow it to self-sow to renew plantings.
Water regularly until established and during dry periods, but avoid saturated soils.
Slightly acidic to slightly alkaline; if soil is very acidic, add lime before planting.
Mix in 2-4" of compost prior to planting.
Diseases & Pests:
Prevent fungal problems buy planting in a location that has good air circulation and well-drained soil.
When to Cut for Bouquets:
Harvest when 1/2 of the florets are open.