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Planting, Growing, and Caring for Delphiniums
Delightful delphiniums! 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.
About Delphinium Flowers
Delphinium is a genus in the Ranunculaceae family. (They鈥檙e often confused with larkspur, but these are 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.
Image: Edita Medeina/Shutterstock
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鈥檚 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
- Delphinium 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.
Credit: Arty Alison/Shutterstock
Catherine Boeckmann
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Yellow leaves with green veins is typically an iron or manganese deficiency, which are not typically found in commercial fertilizers. However, it may be that the pH is off and those micronutrients are in the soil, but not available to the plant. There are simple pH testing kits that you can buy at most gardening stores. Make sure that the pH is between 5.8 and 6.5, which is where most plants like it to be.
About 2 weeks ago I bought some Delphiniums at the local big box store. I wonder if they have leaf miners? All the older leaves have dead brown edges that curl under. I don't see little lines of eggs on the back, nor actual trails I can follow moving across the face of the leaf. But large areas of the leaves are covered with light tan speckles and thin lines. The area is thickened and very stiff, with a heavy, bumpy texture on the top surface. Can anyone confirm, please?
I live in North Florida and you can imagine the summers are hot and muggy. I know it's said that growing from seeds is difficult, but I'd like to try. Do you have any tips (if seeds do their thing) for care in this climate? I'm just concerned because: "They prefer moist, cool summers and do not fare well in hot, dry summers." and I'm a mix of the two...the better two I hope. Thank in advance.
I never had any luck until I planted them in a nursery bed in the fall and let them overwinter. I imagine in Florida you'd have to refrigerate the seeds before planting them out.
Use mycorrhizal fungi when planting and in watering. They are EASY to start and grow this way.
I have started these from seed and it is difficult but not impossible. I live in Idaho, started seeds in the early early spring. It would have been better if I had put plastic over the pot after planting seeds as a sort of hot house, you may not need to do this with your humid weather in Florida tho. Many came up but not many survived to transplant size. Good luck!
Jacksonville...I got about two months of beautiful blooms. Started in the fall last year.
Hi Chellina,
In Florida delphiniums are best planted in mid- to late autumn or very early winter for spring blooms during the cooler months. They will probably not survive your humid hot summers.
I purchased a couple of Delphinium plants from Lowes on clearance because they were a little brown. I assumed they were dry and just needed to be watered so I purchased them and mixed in Miricle Grow with the soil. I watered them and kept the soil moist. They did alright for a week but then they all turned brown (stalks and leaves). When I LIGHTLY pulled on the stalks they broke off at ground level. Did the Delphinium's die or will they come back next year?
I believe what happened is you put a fertile too high in nitrogen the best fertilizer for transplanting new plants is hastagro organic fertilizer or Bills Perfect Fertilizer because it reduces transplant shock. You need something around and (not exactly ) 5-10-12
