Oh, the delightful delphinium! The stalwart of many summer flower gardens, these showy perennials are grown for their long, colorful spikes in blue and other gorgeous hues.
Flowering all summer, delphiniums are butterfly and hummingbird magnets, too! Learn how to plant, grow, and care for delphiniums.
Delphinium is a genus in the Ranunculaceae family. (They’re often confused with larkspur, which are a different plant species.) There are more than 300 delphinium species, so there is quite a variety of heights, from dwarf hybrids to 6-foot tall beauties, so they can be planted in the front, middle, or back of a perennial border. The blue delphinium is most common, but varieties also come in gorgeous shades of violet, pink, white, red, and purple. They are popular in both cottage-style and cutting gardens.
Most delphiniums are short-lived perennials, lasting 2 or 3 years in the garden. Some varieties will bloom throughout the entire summer if the plants are cut back regularly. Other hybrids bloom from early to mid-summer and will produce a second flower display in late summer or early fall if you cut off the old flower stalk.
What’s important to know about delphiniums is that they will thrive if you meet their specific conditions. Delphiniums prefer moist, cool summers; they do not fare well in hot, dry weather or sudden wind or rain, which can knock them down. Most varieties will need staking. See more details below.
Are Delphinium Poisonous?
Yes, delphiniums are highly poisonous. If seeds and seedlings are ingested, they can cause nausea, twitching muscles, paralysis, and even death. This is mainly a concern for grazing animals such as cattle, horses, and sheep, and it is also a caution to gardeners with small children.
Growing
- Delphiniums are heavy feeders. Apply a balanced liquid fertilizer starting in early spring every 2 to 3 weeks.
- Insert sturdy stake supports no later than mid-spring or when the plants reach 12 inches high.
- Do not allow the soil to dry out, but avoid puddling. Water plants during the summer if rainfall is less than 1 inch per week.
- For ideal flower spikes, thin side shoots at 3 inches high, leaving 2 or 3 shoots on young plants and 5 to 7 shoots on mature, well-established ones.
- Deadhead by cutting spent flower spikes back to small, flowering side shoots.
- After delphiniums have finished blooming, cut flower stalks to the ground, and new, though smaller, flower stalks will develop. The flowers will survive the coming cold days and even light frosts. (See local frost dates.)
- Every 3 to 4 years, divide plants in spring: Remove and replant the new little plants growing around the outside of the clump. Discard the hard old heart.
Types
- Belladonna Group: blue flowers native to North America; easier to grow and longer-lived than varieties in the Elatum Group (below); upright, loose, and branching perennials; secondary flower spikes extend bloom period into autumn; 3 to 4 feet tall. ‘Blue Donna’ has clear, blue flowers.
- Elatum Group: tallest varieties in shades of violet, blue, pink, and/or white; short-lived; reach 6 feet tall or more. ‘Aurora Deep Purple’ has purple flowers with a white center.
- Pacific Hybrids: 3-inch violet, blue, and pink flowers; short-lived; tolerate warm/hot climates as annuals; giant (3- to 6-foot) heirlooms and dwarf hybrids. ‘King Arthur’, 5 to 6 feet tall, has plum flowers with white centers.
More Like This
Delphinium are only harmful if ingested, so rabbits and deer would be most likely to be affected. Generally, these animals will only take a nibble of the plant (not enough to harm the animal) and then be turned off by the unpleasant taste. If these grazers visit your garden regularly, consider covering the delphinium while they're young (and most toxic) or planting them in a container that can be placed out of reach.
Both plant are considered deer-resistant and good choices in gardens without fencing. (Just keep in mind: NO plant is truly deer-resistant if deer are hungry enough; however, some plants are more resistant than others.)
No worries. Delphiniums are a hardy herbaceous perennial, which means they are fully hardy down -10 to -15C and between 5 - 14F. In late autumn and winter they die back completely to bare earth and regrow each spring. Note: They do need shelter from winds and best planted in a sheltered spot away from winds. They have heavy flower heads supported by hollow stems. Also, all delphiniums need staking as soon as they have put on growth and are getting established.
Kudos for getting sprouts, Jack. Height is a consideration but you want seedlings with "true" leaves, not just the two that initially appear. True leaves appear early, so if your plants have a couple to a few inches, you're probably well past that stage. As for height, we've see suggestions of 12 to 15 inches but it depends on the strength of the plants. Before transplanting you also want to harden off the plants—get them used to the world. Here is some advice on that https://www.almanac.com/video/how-harden-plants and another https://www.almanac.com/news/gardening-news/time-get-tough-hardening-plants (these are about vegetables but the process is the same).
We hope this helps!
- « Previous
- 1
- 2
- …
- 10
- Next »
Comments