Delphinium Dark Blue

Delphinium cultorum

Delphinium are a striking addition to the garden and ‘Black Knight’ offers an exceptionally deep blue-violet hue with a dark black center. The tall stems add color and height to the back of gardens and can be used in floral arrangements. Plants attract a variety of pollinators and are deer resistant.

Plant Height: 4-6’

Light Requirements: full sun

Soil Preference: rich, well draining soil, pH 6.5-7.5

USDA Zones: 3-9 (perennial)

How to Grow

Germination: 14-28 days at 65-70F

Seeding Depth: 1/4”

Plant Spacing: 2-3’

Days to Maturity: Flowers in the second year

Early-Season Seeding: Start seed indoors 4-6 weeks before the last frost date, transplant after the danger of frost has passed. Direct seed outdoors after the last frost date or when soil temperature is above 60F.

Late-Season Seeding: Start seed indoors or direct seed outdoors at least 12 weeks before the first frost date.

Growing Tips: Delphinium requires support of the tall stems in windy locations to prevent them from breaking. Plants may need to be replanted every 3-5 as their vigor can decline with age. Cutting flowers back after they flower in summer may result in a second flush of blooms in the fall.

Cut Flower: Harvest when the bottom ⅓-½ of the blooms are open. Flower food will result in a vase-life of 7-10 days.

Photo by @northernlight_garden