Learn how to grow delphiniums to enjoy their stunning summer flowers.
These elegant plants also add a strong vertical element to cut flower bouquets.
This guide covers what you gotta know to grow delphiniums in your own garden.
Credit:David McDonald
Delphinium plants and seeds are toxic.Plant them in a location away from children and pets.
Plant delphiniums in well-draining soil in an area that receives6 to 8 hours of sun daily.
Use the plants in cottage gardens or anywhere you want to invite pollinators to your landscape.
Credit: Mike Jensen
How and When to Plant Delphiniums
Spring and early autumn are the best times to plant delphiniums.
Dig a hole the same depth as the plants nursery container and at least as wide.
They enjoy rich soil, soadd compostto the planting holes.
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Position each plant so the top of the root ball is level with the soil surface.
Light
Delphiniums should beplanted in full sunfor the best blooms and sturdiest stems.
In areas with hot summers, delphiniums benefit from some afternoon shade.
Credit: Greg Ryan
Standing water can lead to crown rot, which causes the plants whole base to rot and eventually die.
However, if there is ample rain, they shouldnt need supplemental watering.
If youre lucky, they may come back as the weather cools.
Credit: Marty Baldwin
In anythingwarmer than Zone 7, these plants are typically treated as annuals.
However, afternoon shade, mulching, and selecting heat-tolerant varieties can mitigate some of these issues.
Compost tea is also effective.
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Cut the flower spike off right above the first set of leaves below it.
Leave any side shoots and remaining foliage on the base of the plant.
After the plant is completely done blooming, cut the stems back to about 6 inches above the ground.
Credit: Mike Jensen
This will encourage fresh new growth and possibly a few more flowers in the fall.
Powdery mildew, botrytis, and leaf spot are all common problems that delphiniums struggle with.
Also avoid overhead watering as much as possible to keep the leaves dry.
Credit: Marty Baldwin
Instead, aim the water at the soil at the base of the plant or use drip irrigation.
Because these plants are tall, wind and rain can snap the flower stems.
Use staking or other supports to protect the flower spikes.
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Place stakes before flowers appear, and loosely tie the stems as they grow with twine.
Deer and rabbits aren’t usually a problem, but they may nibble your plants from time to time.
Delphiniums areknown to attract slugs.
Handpick them when you notice them, or useslug bait trapsto get rid of them.
Types of Delphinium
Several species and hybrids of delphiniums are available.
Here is a small selection to consider growing.
It tolerates heat better than other delphiniums, blooming through most of the summer.
It hasreddish-purple flowerswith a creamy white center called a bee.
Colors range from light blue to white, pink, and purple.
Zones 3-7
Summer Stars Delphinium
Delphinium grandiflorumSummer Stars is a dwarf variety that producespure-white flowersin summer.
It grows 12-14 inches tall.
Zones 4-7
Summer Morning Delphinium
Delphinium grandiflorumSummer Morning is the first truepink varietyof Chinese delphinium.
It grows 12-14 inches tall, blooming all summer long on well-branched plants.
It prefers moist soils, but its extensive root system tolerates drought well.
Its a large plant, growing 4 to 6 feet tall.
Like delphiniums, this perennial works especially well in cottage garden plantings.
Numerous varieties are available that bloom in other colors such as pink or orange.
Plants grow about 2-5 feet tall in Zones 4-10.
The large clusters of pink, purple, or white flowers attract pollinators, especially butterflies and hummingbirds.
Plants grow 2-4 feet tall in Zones 4-8.
Summer Cottage Garden
This eye-catching, long-blooming garden plan adds interest and drama to your yard.
Stately delphiniums are the backbone of this colorful cottage garden plan.
Garden size: 20 by 10 feet.
However, in warm areas, they are usually grown as annuals.
It depends on the variety you select.
The tallest of the delphiniums benefit from staking to protect them from wind damage.
North Carolina State University Extension.
