Adding splendor and architectural height to borders, Delphiniums (Larkspurs) are elegant and stately perennials, biennials or annuals, which form incredibly eye-catching spikes of single or double flowers in early-mid summer and often rebloom in late summer or early fall. Profuse bloomers, their regal blooms come in an array of gorgeous colors including blue, white, pink and violet, the blue varieties being highly prized by gardeners. Rising from a mound of divided, pale to dark green foliage, hummingbirds are endlessly attracted to them - as most onlookers!
- Delphiniums may be planted in spring
- Delphiniums grow best in cool and moist summer climates, and do not fare well in hot, dry summers
- Delphiniums need at least a half-day of sun (minimum of six hours of sun a day). Full sun is ideal as Delphiniums bloom best in sunny spots except in the South, where afternoon shade is appreciated.
- These plants require excellent drainage. In poor or heavy soil, add organic matter at planting time to improve drainage.
- Delphiniums love fertile, rich, moist soils. They are heavy feeders so the more compost you add to your flower bed the more spectacular your Delphiniums are likely to be.
- Provide a site sheltered from strong winds and sufficient space to ensure good air circulation. Don't let your Delphiniums be shaded or crowded by their vigorous neighbors.
- Loosen your garden soil with a garden fork or tiller to a depth of 12-15 in. (30-37 cm), then mix in 2-4 in. (5-10 cm) of compost.
- Space your plants 1 to 3 ft. apart (30-90 cm), depending on the variety.
- Dig a hole twice the diameter of the pot your Delphinium is in
- Place your plant in the hole so the top of the root ball is level with the soil surface.
- Backfill the hole and firm the soil gently. Water thoroughly.
- Delphiniums may be grown from seed, but this can be quite challenging. Seed should be started indoors early in the year, and those plants will flower the first year. If seeds are sown directly in the ground, those plants will not flower until the following year.
Caring for Delphinium
- Delphiniums require regular watering, specifically during the dry summer months. Soil should stay just barely moist and never dry out, nor become soggy.
- Apply a balanced liquid fertilizer every 2-3 weeks.
- Apply a thin layer of compost in the spring as well as a 2 in. layer of mulch to keep moisture and control weeds.
- Stake tall varieties, no later than mid-spring or when the plants reach 12 in. high (30 cm) to prevent the flower spikes from flopping over in case of winds. Grow-through supports work well for Delphiniums, as do cages.
- Thin shoots when 3 in. high to ensure good-quality flower spikes. Leave at least 2-3 shoots on young plants and 5-7 shoots on well-established plants
- Remove spent flower spikes to promote additional blooms.
- After the first killing frost, cut stems back to the ground.
- Divide plants every 3 to 4 years as new growth begins in the spring, lifting plants and dividing them into clumps.
Pests & Diseases
- Susceptible to slugs and snails as well as cyclamen mites.
- Powdery mildew, Southern blight, bacterial and fungal spots, gray mold, crown and root rot, white rot, rust, white smut, leaf smut
- To avoid most of these diseases and pests, practice good sanitation around the plants and keep their area well drained and clear of debris.
- All parts of the plant may cause severe discomfort if ingested.