Delphinium: Everything You Need to Know About Planting and Care

By Beth Krietsch

With eye-catching colorful blooms that extend upwards in tall spires, it’s hard to deny the unique beauty of delphinium. Growing upwards of eight feet tall, this stunning summer bloom (you’ve probably heard it referred to as larkspur), is a great way to add a colorful vertical element to your garden. It looks beautiful when mixed among other types of plants, both in a garden or as cut flowers.

While delphinium is most commonly seen in shades of blue, there are varieties that produce coral, red, pink, and yellow blooms. Well-loved by hummingbirds, delphinium can be a great choice if you’re looking to attract hummingbirds to your garden. They typically bloom twice each season, once in the early- or mid-summer and then again in the late summer or fall.

One interesting tidbit about delphinium is that they can be toxic to humans if ingested. So this is definitely a flower to leave off your summer salad. Though delphinium aren’t the simplest to grow and care for and do require a bit of attention, their dramatic beauty makes the effort well worth it.  

How to plant delphinium

  • Delphinium should be planted in nutrient-rich, well-draining soil in order to keep them healthy and prevent root rot.
  • Find an area with full sun, as they are more prone to illness and problems with fungus and mildew when situated in an area with lots of shade where they can’t properly dry out.
  • It’s best to leave one to three feet of space between plants, and many people plant them in the back of the garden so they don’t overshadow other flowers.
  • Delphinium can be grown in plant hardiness zones 3–7, but does 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.

Caring for your delphinium

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

  • Moist soil is important for facilitating healthy delphinium, so you’ll need to water your delphinium 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, and 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 has bloomed for the first time in order to encourage another bloom in the late summer or fall.
  • Delphinium are prone to problems with a mildew, crown rot, botrytis blight, leaf spots, and slugs. Delphinium grown in areas with more sunlight are better at resisting mildew, though excessive heat and sun isn’t ideal

A few favorite varieties of delphinium

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 blue, lavender, and mauve colored blooms that are just stunning and make an excellent addition to a bouquet of cut flowers. They are also deer resistant, so great 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 small 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.

Macro of blue delphinium flowers, early morning, June 30, summer, shallow depth of field

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 five feet tall.

King Arthur delphinium (Delphinium ‘King Arthur’)

These delphinium feature bluish or purple flowers with a contrasting white center. They can grow up to about six 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.  

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