Larkspur, also known as Delphinium, is a genus of about 300 species of perennial flowering plants in the family Ranunculaceae, native throughout the Northern Hemisphere and also on the high mountains of tropical Africa. The genus was erected by Carl Linnaeus. Larkspur foliage is silver green on tall stalks surrounded by flower covered spikes. Flower colors include blue, lavender, white and red. Depending on the variety, height ranges from dwarf plants to plants exceeding 6 feet tall. Larkspurs prefer rich, moist well-drained soil and thrive in full sun to partial shade. Dwarf-sized plants are used in borders, garden beds and containers. Taller varieties are often used as cut flowers and dried arrangements. This herbaceous perennial is hardy in USDA zones 4-8. The genus Delphinium is toxic to humans and livestock.
Larkspurs like well draining soil and full sun but can tolerate partial shade. For the best blooms, choose an area that gets full sun. Larkspurs can grow very tall and may need staking to support its heavy blooms. This plant self-sows by dropping seeds and will return the following season. If not properly monitored, Larkspur can take over a garden. It is a good idea to space each plant 16 inches apart from each other.
Larkspur is a fast growing flower and grows best in cooler weather. Typically, delphiniums need regular watering and should not be left to grow in dry soil. Continued moist soil will aid in faster growth. Adding a 2 inch layer of mulch will help to retain the moisture in the soil. During dry periods, water once or twice a week. Be sure that the soil is well draining so the plant is not left sitting in soggy conditions.
Larkspur is a fast growing plant with multiple blooms. Because of this, they are heavy feeders. Prior to planting, mix a general purpose fertilizer into the soil. Once the roots are established, fertilize again. After that, fertilize once a month with a balanced 10-10-10 (NPK) fertilizer until the blooms open. Water well after each application of fertilizer.
Larkspurs can benefit from a light pruning each season. Light pruning keeps the plant attractive and encourages a second bloom. Remove wilted stalks by cutting when ⅔ of the blooms have wilted. You can also deadhead spent blooms to prevent the plant from forming seeds. If you would like your Larkspur to reseed, the refrain from deadheading. A severe cutting in early summer can encourage a second bloom. Pruning helps to winterize the plant as well. Delphiniums are poisonous to humans and some animals. Properly dispose of excess plant material.
Caring For Larkspur in Pots
It is best to choose a compact variety of Larkspur to grow in a container or pot. Choose a sturdy pot that will not fall over from the weight and height of the stalks of flowers. Plants grown in containers tend to dry out more quickly. With Larkspur, it is important to keep the soil continually moist but not soggy. Your container should have good drainage holes. Once the plant is established, staking may be needed to support the plant.
Winter Care for Larkspur
As winter approaches, continue to water the plant regularly until the ground freezes. This gives the roots a chance to store water for the cold weather months. After fall flowering, cut the plant to the basal leaves, leaving the foliage in place. Mulch around the plant to help preserve moisture and insulate the roots. During winter, if the ground thaws, your Larkspur will appreciate a drink of water.