Spring in 2019 in Northern Virginia brought just the right amount of precipitation, and the air temperature warmed slowly and stayed in comfortable ranges for weeks. Consequently, spring flowers lasted for a long time, unlike years when the temperatures rise too quickly.
One plant that benefitted was Consolida ajacis, also known as rocket larkspur. At Green Spring Gardens, larkspur was a standout in garden beds, and we received many inquiries for the name of “that tall blue, purple, lavender … flowering plant out by the gazebo, in front of the glass house, by the traffic circle, etc.”
Consolida ajacis is an annual species, meaning it germinates from seed, grows, flowers, sets seed, and dies within one year. However, it self-sows so abundantly that crops can return year after year. New colonies also develop nearby because seed is transferred by wind, water, people and animals. Allow the flowers to go to seed, and you will have larkspurs year after year.
Consolida ajacis is native to Europe and Asia but was introduced to North America, perhaps by European settlers, and has naturalized in North America. It is grown as an ornamental plant in flower beds, as a cut flower and for drying. It’s not a plant commonly sold in pots in nurseries because it does not transplant well, however, seeds are available through catalogues.
Growing Consolida ajacis from seed is simple. Scatter fresh seed in a prepared flower bed in autumn, and lightly cover the scattered seed with a thin layer of soil or leaf mulch. Make sure the planting bed receives full sun and is moist but well drained. After sowing, lightly water the bed and let it be until spring when seedlings should start appearing. Seeds need darkness and the winter’s cold temperatures to germinate in spring. Once seedlings appear, gently thin them so the remaining seedlings have adequate space to grow. If you have a successful crop, simply let a few plants go to seed before removing them after they die in early summer. Most plants will brown out, die, and set seed in our area by mid-June.
Two species of larkspur are native to Virginia and, unlike Consolida ajacis, are perennials. The first, Delphinium tricorne, sometimes referred to as dwarf larkspur, is a spring ephemeral that breaks dormancy and flowers in early to mid-spring, then returns to dormancy when temperatures rise. It grows in woodlands where it takes advantage of spring sun before the tree canopy leafs out, but it still benefits from some shade. It has blue, sometimes white, and sometimes blue and white flowers, and it grows one to two feet in height. The second native species, Delphinium exaltatum, also known as tall larkspur, prefers full sun and blooms in summer. It can grow from 4 to 6 feet tall and has beautiful blue flowers. In hot, humid areas it does appreciate some afternoon shade.
Native larkspur can be purchased as potted plants or sometimes as dormant bare roots in autumn through specialty nurseries or online. All three species can be grown from seed.
Growing from seed starts in autumn. Seeds can be directly sown in garden beds, however, it may take a year or two for them to flower. It may be easier to care for the seedlings if the seed is sown outdoors in seed flats placed in a protected area or a cold frame. Protect seed flats from digging critters and downpours with a covering of mesh or screening material. Seeds also need the cold of winter to force germination. Once seedlings appear in spring and have developed true leaves, they can be transplanted into nursery pots or nursery beds.
All parts of all three species, including the seeds, are toxic if ingested. This makes them safe from deer and rabbit browsing, but keep them away from small children, pets and grazing livestock. It is best to wear gloves when handling all parts of the plants.
Author Alda Krinsman is the Garden Gate Plant Shop Coordinator at Green Spring Gardens.