Native to England, home flower gardeners are growing delphinium — also known as larkspur — for their beautiful feathery leaves and tall spires of blossoms that bloom all summer long. Available in almost every color, they add grace to borders and are spectacular when planted along a stone wall or garden fence.
Delphiniums (Delphinium elatum) can be difficult to grow even under the best of conditions. However, both tall and short varieties have long been a favorite in cottage-type gardens, mixed perennial beds and floral bouquets. Impressive plants with showy single or double flowers stand up to 6 feet tall. This short-lived perennial prefers partial shade and always draws oohs and aahs from the neighbors. Plants are toxic to humans and livestock, but attractive to hummingbirds.
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Quick Guide: Planting, Growing & Caring for Delphiniums
- Delicate blue, pink, white or purple flowers will be a highlight of your garden
- Need rich soil and full sun to part shade; prefer cooler climates
- Plant from nursery stock or division; sowing seed requires some attention
- Provide consistent water and support for tall varieties
- Expect blooms in midsummer
Sunlight: Full sun to partial shade
Maturity: 85-125 days from seed to flower
Height: 2 to 6 feet
Spacing: 12 to 36 inches apart in all directions
Site Preparation
These “needy” plants do best in sunny locations with rich, well-drained soil. Prior to planting, work a couple shovelful of organic compost and a dry fertilizer into the soil. This helps condition the soil, which improves drainage and will keep roots cool (watch our video 6 Tips for Growing Great Flowers).
Delphiniums are one the first perennials to show new growth in the spring and can tolerate some frost. Large varieties will require support and protection from the wind. Plants do not like hot weather and dry conditions.
How to Plant
May be propagated from divisions or from seed. If planting from seed, sow outdoors two weeks before the last frost, just beneath the soil surface (see Sowing Seeds Directly In the Garden). Seeds will germinate in 14-21 days.
Tip: Chill delphinium seed for a 1-week period prior to planting to improve germination by putting them in the refrigerator. Read our article How to Stratify Seeds and Improve Germination here.
If propagating by division, separate clumps every 2-4 years in early spring. Delphinium will benefit from the cool, wet weather and be well established before the heat of the summer kicks in.
Water well throughout the gardening season and feed with a liquid flower fertilizer to keep plants strong and productive. Pinch off the faded blossoms to extend the flowering season. Mulch to prevent weeds, conserve moisture and improve aesthetics.
Most perennial flowers benefit from division as they get older and begin to lose vigor, plus you get more plants to spread around the garden or share with friends.
Insect & Disease Problems
Slugs and aphids will occasionally attack delphinium. Watch closely and apply diatomaceous earth or other OMRI listed pesticide if aphids are found.
Large irregular holes in foliage and partially eaten seedlings are signs of slug damage. Scatter Sluggo®, an organic iron phosphate bait, around plants to kill slugs and snails without harming people, pets or wildlife.
The leaves and stems of plants are also susceptible to attack by powdery mildew, rust and gray mold. To reduce common plant diseases found on delphinium:
- Avoid overhead watering whenever possible (use soaker hoses or drip irrigation)
- Properly space plants to improve air circulation
- Apply copper and sulfur sprays to prevent further infection
Seed Saving Instructions
Not available
Eric is now retired, but is still a renowned gardener known for his expertise in composting, organic gardening and pest control, utilizing pesticide-free options, such as beneficial insects.
Eric believes when you do something good for the environment, the effects will benefit generations to come.
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