Larkspur, delphinium same but different
Q: Are larkspur and delphinium the same plant?
• Alice from Poland
A: The two plants look similar, but the answer is, no, in fact they are different species, but they are related.
Delphinium tends to be a perennial and larkspur is an annual that will reseed, making it appear as if it may be a perennial. Delphiniums are short-lived perennials, usually lasting two to three years.
Delphiniums are tall spikes of colorful flowers. The largest delphiniums are about six feet tall, perfect for the back of the garden or a stunning centerpiece of a large garden. The shortest ones are less than two feet tall. Delphiniums remind me of a classic English garden. The flowers are violet, purple, white, pink, red and even yellow. I have never seen red or yellow delphiniums, but they exist.
Sow delphinium seeds in fall. The flower spikes are hollow and brittle, so they may need to be staked because wind and hard rain may snap the spikes. Delphiniums bloom from early to mid-summer. Cutting the stalks back after the first bloom usually produces a second bloom. Cut just below the last flower and leave the foliage. New shoots should begin to appear at the base of the plant soon after the spent flowers have been trimmed. You should have a second bloom, but the flowers will be smaller.
Delphiniums prefer a deep, organic-rich soil, but will tolerate most any soil. Full sun makes them happy, and unlike most perennials they are heavy feeders. This is most likely due to the heavy flower production. They may be affected by powdery mildew, botrytis and crown rot, so give them some room and be sure the garden area is well drained. Slugs, aphids, leaf miners and mites are the common insect issues, but I have never had any of these problems. Water deeply and infrequently. I often see bees, butterflies and hummingbirds on my delphiniums. Delphiniums make a nice cut flower and have a good vase life.
Larkspur is another beauty. It has lovely, daintier flower spikes, fewer flowers and fine deeply cut leaves. For best results, put seeds in the freezer for one to two weeks. Sow in early fall in warmed, well-drained soil about a quarter inch deep. They will overwinter as small plants.
Next year, plan to thin seedlings as overcrowding can be an issue on plants that reseed and lead to some disease pressure. The colors are generally the same as delphiniums. Full sun is best. They also make good vase flowers.
Larkspur spikes can be dried to retain color for decoration. Harvest when flowers are about 80 percent of the stalk. Remove foliage, hang upside down in small bunches, in a dark but well-ventilated room. When the flowers feel like thin, dried paper, the stalks can be placed in a vase to finish the drying process.
Know that both plants are poisonous. My best advice — beware, and don’t add any to your salad. For details on delphiniums, go to http://go.osu.edu/delphinium.
McKinley is an OSU Extension Master Gardener volunteer in Mahoning County. Call 330-533-5538 to submit your questions to the plant clinic. Clinic hours are 9 a.m. to noon Mondays and Thursdays. Or visit go.osu.edu/mahoningclinic.