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Delphiniums

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Botanical name: Delphinium

Plant type: Flower

USDA Hardiness Zones: 3, 4, 5, 6, 7

Sun exposure: Full Sun, Part Sun

Soil type: Loamy

Soil pH: Alkaline/Basic


Flower color: Pink, Blue, Purple, White

Bloom time: Summer

Delphiniums are perennials grown for their showy spikes of colorful summer flowers in gorgeous shades of blue, pink, white, and purple. They are popular in cottage-style gardens and cutting gardens.

Delphiniums are a favorite of many gardeners and sometimes a challenge. They prefer moist, cool summers and do not fare well in hot, dry summers. The plants also dislike sudden wind or rain. 

Except for the dwarf perennials, most delphiniums need staking.

Planting

  • Grow in fertile, well-drained soil in full sun to light shade, with shelter from strong winds.
  • Plant in the spring. Prepare the soil, mixing in 2 to 4 inches of compost.
  • Delphiniums are very difficult to grow from seed. Buy as a potted plant at the nursery.
  • Dig a hole twice the diameter of the plant's container. When planting, ensure that the top of the root ball is level with the soil.
  • In the spring, broadcast lime, wood ashes, or a mixture of the two over this alkaline-loving perennial.

Care

  • Insert supports no later than midspring or when the plants reach 12 inches high. Stake the low-growing perennials with twiggy, brushwood support. The taller, large-flowered delphiniums need sturdy stakes.
  • Soil should not dry out. Water plants during the summer if rainfall is less than 1 inch per week.
  • For good-quality flower spikes, thin shoots when 3 inches high; leave a minimum of 2 or 3 shoots on young plants, and 5 to 7 shoots on well-established ones.
  • In growth, water all plants freely, applying a balanced liquid fertilizer every 2 to 3 weeks.
  • 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.
  • If delphiniums need to be divided in the spring, remove and replant the new little plants growing around the outside of the clump. Discard the hard old heart.

Pests

  • 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, and damping off occur.

Harvest/Storage

  • This elegant flower is good for a cutting garden. If you take the blooms into the house as soon as they open, they will bloom again.
  • Add sugar to arrangements of delphinium.

Recommended Varieties

There are dwarf-sized delphiniums and medium-sized as well as tall ones (growing up to 6 feet and higher).
  • Belladonna Group: Upright, loose and branching perennials with single flowers that grow 3 to 4 feet tall. 'Blue Bees' is a Belladonna producing clear blue flowers with white centers.
  • Elatum Group: These are the tallest spiked hybrids growing to 6 feet or more. 'Blue Nile' is a medium plant bearing semi-double, bright, and mid-blue flowers with white centers (called bees). 'Bruce' is a tall Elatum bearing semi-double, violet-purple flowers, paler towards the center, with brown bees.
  • Pacific Hybrids: Similar to Elatum Group, although not as tall, this hybrid is short-lived and often grown as annuals or biennials. 'King Arthur' bears plum flowers with white bees with 5- to 6-foot tall flower spikes.

Wit & Wisdom

  • Very young delphinium plants and delphinium seeds are poisonous. If ingested, they can cause nausea, twitching muscles, paralysis, and even death.

Free E-Card

Send this beautiful blue delphinium to friends and family.

 

 

Comments

By Anonymous on May 5

I am searching for information on delphiniums and what variety might be best to try for my Midwest (Iowa) zone. It sounds like a dwarf variety might be less finicky! Thanks to everyone who comments.

By Anonymous

I have newly potted delphiniums putting out flowering spikes. Should I pinch back or allow to flower?

By Almanac Staff

With newly potted delphiniums, think out flower spikes if they are thinner than a pencil. Leave 1 to 3 spikes per pot. The more vigorous your delphiniums get, the more spikes you can leave.

By Anonymous

My favorite flower! When the first bloom finishes, I cut them back to the ground, and they bloom all over again, I even cut them back after the second bloom and they do it all over again. Always just as spectacular as the first time.

By Anonymous

In front of my house in UK (Kent), there are Delphiniums either side of the front door...was there when we bought the house 20 years ago and are still there. We are now in Bulgaria, where our Delphiniums which we sowed from seed 10 years ago, flower throughout the year and seems to love the intense summer heat....to our great surprise. When Delphinums appear not to be doing anything, or not flowering, dig them up and separate the roots, they are telling you they are rootbound...then you will have loads more to enjoy.

By Almanac Staff

Thanks for the great advice!

By Anonymous

This has been my second year with a delphinium plant bought from a garden centre
This is its second year running producing no flowers, it is strong and healthy and green why is this happening

By Anonymous

Try scratching in a couple tablespoons of garden lime all around the plant, it sounds like the soil is also too acid.

By Almanac Staff

Is your soil poor? Delphiniums enjoy amended soil rich in organic humus. Also, make sure the soil is well drained and not too heavy as this plant doesn't like "wet feet."

By Anonymous

Does anyone know why my delphiniums did not come up this year? Are they gone for good?

By Almanac Staff

If your perennial is over 2 years old then there's a chance that you may need to replace them.

Unfortunately, delphiniums are short-lived and generally do not do well after 2-3 years.

Thank you for your interest in the Old Farmer's Almanac and our Web site.

By Anonymous

I've had a Black Knight Delphinium since 1998, a real beautiful eye catching display in front of my house, south of the porch entrance. Last week the plant is about a foot high, lush green, and I'm visualizing another year of beauty from this plant. Three days later its' leaves are eaten up. Just stems looking at me with a dead appeal. A search reveals greenworms all sizes. I picked them all, some 40 of them. What are they, where do they come from. Have not touched other perrennials next to this delphinium. My corner is naked and feel like I've lost a best friend.

By Almanac Staff

We feel for you. These worms are called green loopers (Autographa biloba). We don't always see problems with this insect but it seems to be very wide spread this year. They not only affect Delphinium, but also Geranium, Salvia, verbena, and other perennials. As you indicated, they should be hand picked, if not too extensive. The worms can be well camouflaged. In the future, there are some sprays you can use, if you're willing, including Sevin, permethrin, orthene. Or, if larvae are under one inch, B.T. sprays such as Dipel or Thuricide are effective. Follow the directions closely.

By Donna Little

Several years ago I planted a Blue Butterfly Delphinium in one pot on my patio. This has become one of my favorite flowers. I've become very acquainted with their foliage and each year I'm thrilled to find them coming back. They have thrown seeds and have naturalized, coming up against a rock wall or on the other side of the house, completely away from the mother plant. In fact, I dug up a wayward plant and transplanted it into a pot in my courtyard. That plant is thriving, too! This plant seems to defy all the recommendations for optimum care. We live in the mountains of New Mexico in an area plagued by high winds, but this little plant refuses to give in. I water it a couple times a week and fertilize it maybe a couple of times during the summer. It provides so much joy each year with it's gorgeous blue blooms. I wish I could have a yard full of it!

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