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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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I recently purchased and planted my Larkspur in a large pot on my patio The flowers are blooming, but the leaves appear to be burning. It gets morning and mid day sun. Any suggestions?
If by burning you mean turning yellow, your plant could be afflicted with a disease and, honestly, there are too many options to cite here. At this link << http://extension.psu.edu/pests/plant-diseases/all-fact-sheets/delphinium-diseases >> you will find a number of conditions, symptom descriptions, causes, and remedies. We hope you can find a solution…without having to destroy the plant. However, if that appears to be the best 鈥渕anagement鈥 as it’s called on this chart (at the link), you should consider returning the plant to the vendor, as the disease may have originated there, or at least telling the vendor of your experience.
I bought one and it is dying I keep it watered what am I doing wrong
I bought one and it is dying I keep it watered what am I doing wrong
I cut my first set of very tall and bountiful blooms down and the shoots that are coming up now are already set to flower. However the spikes are significantly shorter and have many less buds. Are they usually supposed to have this happen?
It is typical of delphinium’s second bloom stalk to be smaller than the first. Take heart in the fact that you are doing everything right: Some gardeners find this a difficult plant to grow!
I live southeast Houston and I purchased my delphinium about a month ago. I had to cut down one spike that had already flowered a week after while another was shooting up. I also managed to get rid of its cyclamen mite infection by giving it a hot water bath for 30 minutes. My question is regarding the new growth that is yellow with green veins and a lot of is drooping. The other spike is now flourishing but shows no sign of distress. I have given the plant plenty of compost and regularly bury 3 banana peels in the soil every week. Could it be that I didn't water it enough? Could it have anything to do with the very small amount of diluted urea I gave the plant two days ago? Am I applying too much neem oil? Also, what is 1 inch of rain per week in gallons?
All in all, the plant has been through a lot during its month in your care: A stalk was amputated. It was soaked in hot water. Why the bananas? These are traditionally said to benefit to roses (and some dispute this). Diluted urea? Why? Neem oil? Why鈥攄oes it have looper worms? (Search 鈥渘eem鈥 on this page for more on this.) Has the plant had time to get acquainted with its new home? Does it get sun? It sound like you’ve watered it plenty. Is the soil damp? If so, it’s watered. One-inch of rain per week is watering until the water soaks down 1 inch. You should just water when it is dry. Delphiniums do not like 鈥渨et feet.鈥 We suggest that you read the care tips above and the reader comments and our responses below.
About the new growth that is yellow with green veins and is drooping: this may be a sign of an iron or magnesium deficiency and/or it could be a sign of improper pH. Do a soil test; you want a pH that is at least slightly alkaline.
You should also consult your local cooperative extension. Click here http://www.almanac.com/search/site/cooperative%20extension chose your state, and find the service nearest you. The folks here are very helpful!
After the other stalk had been spent, I decided to cut it to make another shoot sprout later in the year. I gave it banana peels because I read that they are great organic fertilizers with high potassium and phosphorous amounts that encourage healthy blooms. I gave it diluted Urea for the high nitrogen count and Neem oil to prevent the return of the Cyclamen Mites, powdery mildew, and other diseases. I've also applied an iron/magnesium/zinc solution to the foliage per the label's instructions for faster and safer absorption. It was a very damaged plant when I first bought it so I tried to give it extra care aside from the plants natural high demands. The PH is right around 6.2.
I tried to keep the soil moist per all the discussion posts I've read but it gets very hot and windy in Houston and the plant would often dry out so fast that I wouldn't be able to keep up with it. Anyway I kept it in partial shade and watered it each time 1 inch of topsoil dried out.
The problem is that I was advised to never let it dry out but constantly keeping it moist might have let to root or crown rot. However I don't see any fungus, there's no pungent smell, and the plant is otherwise flowering through side shoots off the second stalk. I've tried to control its environment but this Delphinium has been a very challenging experiment. I'll apply some more iron application and keep the moisture level even but is there any other preventative measures I can take?
Our only thought is, as noted above, to contact your local cooperative extension and ask the advice of experts there. Being 鈥渙n the ground鈥 and familiar with local conditions they may have insights or comments.
