Grow Rocket Larkspur From Seed with Our Easy Germination Tips

Rocket Larkspur is a beautiful heirloom flower with spikes of colorful blooms that can grow up to 3 feet tall. When grown in masses, larkspur makes a statement along a fence or in the back of a flower border. But the unusual flower shape deserves further close-up inspection. Learn how to grow this unique and beautiful flower in your garden.

Although sometimes called Wild Delphinium, Rocket Larkspur is a unique flower with a few differences.

Rocket Larkspur is an annual heirloom with airy and fern-like leaves. The blossoms grow on a spike like delphinium, but they are more loosely spaced on the stem.

The shape of each larkspur blossom looks like the claw of a lark or the spur on a boot, which its name describes. Rocket Larkspur flowers are appreciated for their long-lasting blooms in cut flower arrangements. It also makes a beautiful dried flower. Their unique shape and colors make Rocket Larkspur a favorite for many flower growers.

Larkspur is an easy flower to grow, and with our seed-starting tips, you’ll soon be enjoying this delightful flower in your garden.

Larkspur seeds can be directly sown outside in the late fall or early spring.

To sow Larkspur seeds outdoors, choose a sunny spot with well-draining soil. In growing zones with mild winters, Larkspur will grow and bloom year-round. Temperatures between 50 and 65ºF are optimal for germinating and growing Larkspur.

When sowing Larkspur outdoors in early spring, sow seeds when soil temperature is above 50º and less than 65ºF.

Larkspur seeds can be started indoors 8-10 weeks before the last frost date.

• Chill Larkspur seeds in the refrigerator for 7 days.

• Plant seeds ⅛” deep.

• Keep seeds dark and moist until they germinate.

• Be patient. Larkspur seeds can take 14 to 30 days to germinate.

• Keep soil temperature cool - Less than 65ºF (55ºF is optimal).

• Keep seedlings cool until planting outside.

Larkspur seedlings are ready to transplant once they have one set of true leaves.

Hardening off seedlings is a crucial step for helping indoor seedlings survive the transition to the garden. Start with placing the Larkspur seedlings outside for an hour a day. Increase the time by an hour each day while keeping them sheltered from extreme sun and wind.

After all danger of frost has passed, transplant the Larkspur seedlings into well-draining soil with plenty of organic matter. 

Space plants about 6 to 12 inches apart in full sun.

Rocket Larkspur needs full sun to bloom but is also a cool-weather flower. It will bloom and grow better when temperatures are moderate.

In hot weather, keep the soil moist and cool. Using mulch can help conserve moisture and keep the ground from heating up. Even some afternoon shade can help.

Larkspur are tall flowers that can be knocked down in the wind. You can use flower netting to help hold them upright. Some flower gardeners like to plant them close together, about 6 inches apart, so that they can help hold each other up.

Larkspur isn’t susceptible to any specific diseases other than those commonly found in overly wet soils. 

Growing Larkspur in full sun and watering plants without wetting the leaves will help avoid powdery mildew, crown rot, and botrytis blight.

Larkspur is toxic when ingested, so deer, rabbits, and other animals will avoid it.

However, aphids and slugs can be a problem. If you notice aphids on your Larkspur plants, use natural methods to get rid of them.

Larkspur flowers are beautiful in cut flower arrangements. They can be used fresh or dried.

Rocket Larkspur blossoms open from the bottom to the top. When harvesting Rocket Larkspur for fresh flower arrangements, cut the stems when about ⅓ of the blooms are open.

The best time to harvest Larkspur flowers is in the morning after the dew has dried but before it gets hot. For more tips on cutting flowers, read here.

Larkspur is also beautiful as a dried flower. When harvesting it for drying, cut the stem when almost all the blooms are fully open. Pull off all the extra foliage and hang upside down to dry.

At the end of the season, you can let the Larkspur go to seed. You can either collect the seeds to plant or allow them to fall, and they’ll sprout and grow in the spring.

Larkspur are annuals but will drop their seeds and sprout again in the spring.

One main difference between Rocket Larkspur and Delphinium is that Larkspur is an annual, and Delphinium is a perennial. The blossoms on a delphinium are closer together than on Larkspur. Larkspur is also a little easier to grow. And if you grow heirloom Larkspur, it will self-seed and come back.

Rocket Larkspur can grow up to 3 feet tall. They will spread more if spaced out.

Larkspur is toxic to both humans and animals when ingested.