Delphiniums: Everything You Need To Know About Planting and Care

As an avid gardener who has grown delphiniums for several years, I know the best ways to plant and care for these stunning flowers. Delphiniums, with their towering spikes of vibrant blooms, can transform any garden into a breathtaking display. However, many homeowners have trouble growing them. In this guide, I’ll walk you through the steps to successfully plant and care for delphiniums, so these eye-catching perennials will make your garden flourish.

How To Plant Delphiniums

You should plant delphiniums in nutrient-rich, well-draining soil to keep them healthy and prevent root rot. Find an area with full sun and no shade. They’re more prone to illness and problems with fungus and powdery mildew when you plant them in shaded areas where they can’t properly dry out. I recommend leaving 1 to 3 feet of space between plants, and many people plant them in the back of the garden so they don’t overshadow other flowers in their garden design.

You can grow delphiniums in USDA plant hardiness zones 3 to 7, but these plants do best in mild weather and tend to die in excessively hot temperatures. They’re usually a good choice in regions known for cooler summers without excessive humidity or dryness and typically bloom in late spring or early summer. Most newly planted delphiniums don’t bloom in the first year.

Caring for Your Delphinium Flowers

Caring for delphiniums is a bit more hands-on than with some other garden plants. To grow healthy, thriving delphiniums, here are some tips to keep in mind:

• Moist soil is important for facilitating healthy delphiniums, so you’ll need to water regularly. Add mulch to the soil if you’re having trouble maintaining its moisture.
• Water at the base of the plant to keep the leaves dry and prevent issues with fungus and mildew.
• For taller varieties, you’ll often need to provide support to keep tall delphinium upright. Staking is helpful. Without it, delphinium will often break or fall over, especially in areas that are subject to a large amount of rain and wind. In fact, it’s best to plant them in an area that’s sheltered from strong winds.
• Deadhead delphinium after it’s bloomed for the first time to encourage another bloom time in the mid-summer or fall.
• Delphinium are prone to problems with mildew, crown rot, botrytis blight, leaf spots, and slugs. If you grow the plant in a sunny area, it’ll better resist mildew, though excessive heat and sun aren’t ideal.

Propagating Delphiniums

Propagating delphiniums is a rewarding way to expand your collection. The most common ways to propagate them are division and seed propagation. To divide, carefully dig up the plant in early spring or fall and separate the root ball into sections. Each section should have healthy shoots and roots — replant immediately.

For seed propagation, collect delphinium seeds from spent flower spikes in late summer, sow them in trays filled with seed-starting mix, and keep them moist until germination occurs, typically within 14 to 21 days.

Overwintering Delphiniums

Proper overwintering helps delphinium survive in colder regions. After the first frost, cut back the foliage to about 6 inches above ground level. Apply a thick layer of mulch around the base of the plants to protect the crown and roots from freezing temperatures and wind.

If you have harsh winters, I recommend adding an extra layer of protection by covering the mulched plants with burlap, dried leaves, or evergreen branches. Then, remove these coverings gradually in spring as temperatures warm up.

Delphinium Varieties

Delphinium grow in more than 300 varieties of annuals, perennials, and biennials. Here are a few types you may want to experiment with growing in your garden.

Guardian Lavender Delphinium (Delphinium Grandiflorum ‘Guardian Lavender’)

This perennial produces delicate light blue, lavender, and mauve-colored blooms that are stunning and make an excellent addition to a bouquet of cut blue delphinium flowers. They are also deer-resistant, so they’re ideal for those looking to keep critters out of a garden.

Summer Stars Delphinium (Delphinium Grandiflorum ‘Summer Stars’)

This type of delphinium is unique in that it grows lower to the ground than other varieties. Typically producing white flowers, this dwarf variety of delphinium rarely exceeds 12 or 14 inches tall.

Summer Morning Delphinium (‘Delphinium Grandiflorum ‘Summer Morning’)

These are another smaller and shorter variety of delphinium that usually grows only around a foot tall. They yield delicate light pink flowers that look wonderful in rock gardens or in containers.

Candle Delphinium (Delphinium Elatum)

Often known as candle larkspur, this perennial delphinium variety usually appears in shades of deep blue or purple (but can also be red or orange) and can grow up to 5 feet tall.

King Arthur Delphinium (Delphinium ‘King Arthur’)

These delphiniums feature bluish or purple flowers with a contrasting white center. They can grow up to about 6 feet tall and prefer full sun (that is, at least six hours of direct sun each day) and well-draining soil, like most other delphinium varieties.

Final Thoughts on Delphiniums

Planting and caring for delphiniums requires attention to detail and a bit of patience, but the results are well worth the effort when you have a perfect cottage garden or flowering yard. By following my guidelines, you’ll be able to successfully grow these magnificent flowers. Remember, the key to thriving delphiniums lies in providing them with the right growing conditions, consistent care, and protection from pests and diseases.