How to Grow Larkspur from Seed

Larkspur is a cool-season annual that blooms between late spring and mid-summer. Learn how to grow larkspur from seed in this article!

Larkspur is a gorgeous annual flower that produces tall stems with dense, spiky clusters of violet, blue, or white flowers. Blooms appear at the end of spring or early summer and typically peak around June. 

Larkspur is a member of the Delphinium genus and easily re-seeds and spreads once you plant it. However, it's easy to control by pulling up unwanted plants, so it’s not likely to take over the landscape.

Larkspur can be a bit fussy to grow, and taller varieties need staking. Nonetheless, it rewards you with stunning flowers that attract pollinator insects and hummingbirds.

Want to learn how to grow larkspur from seed? Let's get started!

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Larkspur at a Glance

Common Name	Larkspur
Botanical Name	Delphinium genus
Blooming Season	Late spring to mid-summer, peaking around June
Plant Type	Cool-season annual
Planting Time	Spring in cold regions; September or October in warmer areas
Soil Type	Well-drained, with moderate organic matter; slightly alkaline
Soil Preparation	Amend with compost, manure, or lime if needed
Sun Exposure	Full sun; protected from strong winds
Seed Treatment	Cold stratify in refrigerator at 35°F for a week
Seed Planting Depth	¼ inch, needs darkness to germinate
Seed Spacing	6 to 8 inches apart
Germination Time	14 to 21 days
Watering Needs	Moderate; avoid wetting leaves to prevent mildew
Pests	Slugs, snails, aphids
Common Diseases	Powdery mildew, leaf spot, crown rot
Special Care	Stake taller varieties; deadhead spent flowers; prune after flowering
Maintenance	Thin self-sown seedlings; avoid overcrowding
Lifecycle	Dies back in summer heat
Pollinator Attraction	Attracts pollinators like bees and hummingbirds

Larkspur Varieties

Larkspur is a native species with many hybrid cultivars, including annual, biennial, and perennial. You can often find larkspur blooming in the wild in cool woodlands and mountains, giving you an idea of the growing conditions it prefers. 

Many larkspur seeds and plants are hybrids, including white, mauve, and pink colors and semi-double and double flowers. However, when you save seeds from these types, the flowers of the next generation will likely revert to the purple or blue colors of the parent stock.

Here are a few of the many larkspur cultivars you can find:

• ‘Guardian Lavender’ is a medium-height, early bloomer with double flowers.
• ‘Dwarf Larkspur’ is a low-maintenance plant that does not need staking as it only reaches about a foot tall. It blooms early in April and May. 
• ‘Galahad’ is a long-lived variety with snow-white flowers that bloom from early to mid-summer. 
• ‘Red Lark’ is a rare red larkspur of medium height and early bloom time.

This year, I'm growing Smokey Eyes larkspur from Floret. It has cool lavender blooms on stems up to four feet tall that will look gorgeous along our front yard fence.

How to Plant Larkspur Seeds

These plants can be a little picky about their growing conditions. Keep these tips in mind when growing larkspur from seed.

Direct sow larkspur seeds outdoors

Larkspur has a long tap root and does not like being transplanted. Therefore, it’s best to sow seeds directly where you want them to grow. Choose a location with full sun, excellent soil drainage, and moderate amounts of organic matter.

If the ground lacks organic material, dig in some compost or aged manure. Larkspur likes slightly alkaline soil, so amend with lime to correct the pH if needed. Also, choose a site protected from strong winds or provide the plants with support, such as a fence.

Chill larkspur seeds before planting

For the best germination rates, chill your seeds in a zip-lock bag in the refrigerator at 35°F for a week before planting. This process is called cold stratification, and it replicates a winter season to signal the seed to start sprouting.

Another thing to consider is that the plants need a period of cool temperatures in early life to initiate flowers. Ideally, they should have temperatures above freezing but below 55°F during the first six weeks of development.

So, you must carefully time the planting to match temperatures in your area. You can often meet these requirements in warmer locations by directly sowing the seeds in September or October. In colder regions, planting seeds as soon as the soil is workable in spring usually gives them the cold period they need for optimum flowering.

Larkspur seeds need darkness to germinate

Space seeds 6 to 8 inches apart, and cover them with ¼-inch of soil because they need darkness to germinate. Keep the planting area evenly moist until the seedlings appear in 14 to 21 days. 

Caring for Larkspur

Since larkspur grows in the cool seasons, it usually does not need much watering. However, provide supplemental water if conditions are dry. Water the plants at the bottom without getting the leaves wet to prevent mildew. Also, watch for slugs, snails, and aphids damaging the plants.

Larkspur is prone to several plant diseases, including powdery mildew, leaf spot, and crown rot. To avoid these, establish plants in full sun with good drainage, and avoid planting the seeds too deeply in the soil.

If you let larkspur self-sow for next year, thin out seedlings to prevent overcrowding, or the plants will likely not thrive and flower much. With care, you can sometimes successfully dig up tiny seedlings and move them to new locations, but do so as soon as the seedlings have their second set of true leaves to avoid disturbing the taproot.

Larkspur does best with some maintenance, such as dead-heading spent flowers, staking tall plants, and pruning stems after flowering to encourage more blooms. When the summer heat arrives, the plants will die back and make room for those warm weather annuals!