How to grow Delphinium

Delphinium elatum · larkspur

Tall perennial with dense spikes of blue, purple, pink or white flowers, 0.9–1.5 m high, for borders and cutting. It flowers in early to midsummer and often again in autumn if cut back; plants raised from seed first flower in their second summer. All parts are poisonous to people and pets.

Quick facts

Type	Flower
Family	Ranunculaceae
Light	Full sun
Soil pH	6.5–7.5
Frost	tolerates light frost
Soil for sowing	from 5 °C
Germination	14 days
Seedlings ready	45 days
Where it grows	Open ground

When to plant

Sow for seedlings about 8 weeks before planting out.

It tolerates light frost: plant out in open ground about three weeks before your last spring frost.

Frost dates · When to plant

Care

Open ground

Stage	Watering	Temperature	Feeding
Seedlings	every 3 days	—	—
Growth	every 7 days	—	—
Flowering	every 7 days	—	potassium, at the start of the stage

Growing notes

Light

Full sun; flowering is poor in shade. In hot summers some afternoon shade helps, and plants do best where summers are cool.

Soil

Fertile, humus-rich, well-drained soil that stays moderately moist; neutral to alkaline soil suits it (about pH 6.5–7.5).

Care

Sow fresh seed in pots at about 13 °C in spring; seedlings appear in about 14 days and the plants flower about 18 months later. Protect young growth from slugs and snails. Plants 1.2 m or taller need stakes and shelter from wind. Water new plants through their first summer, and established ones in dry summer weather. A high-potassium feed such as tomato feed helps, especially in containers. Cut faded spikes back to the leaves for a second flush. Wear gloves, as the sap can irritate skin. Watch also for powdery mildew.

Pests and diseases of Delphinium

Sources

Figures checked against these sources.