Delphinium is a striking flowering perennial. Some varieties can grow up to 8 feet (2 m.) tall. They produce spikes of stunning small flowers in blue, deep indigo, violent, pink, and white. Delphinium is popular for cut flowers and cottage style gardens, but they do require a good deal of work. If you’re prepared to put in the time, start with seeds.
Growing Delphiniums from Seed
Delphinium plants are known for being high maintenance, but they reward you with stunning flowers. Knowing how and when to sow delphinium seeds will set you on the right path to growing tall, healthy, flowering plants.
Germinating delphinium seeds requires a cold start so put your seeds in the refrigerator for about a week before planting. Start seeds indoors about eight weeks before the last frost of spring. Alternatively, sow seeds directly in flower beds in early summer.
If sowing outside, you may want to let the seeds germinate first. Put the seeds on a wet coffee filter and fold in half so that the seeds are inside. Place this in an out of the way place but not necessarily in the dark. In about a week you should see little roots emerging.
Whether you’re sowing delphinium indoors or out, cover the seeds with about an eighth of an inch (one-third cm.) of soil. Keep the soil moist and at a temperature of about 70 to 75 degrees F. (21-24 C.).
How to Plant Delphinium Seedlings
Delphinium seed planting should lead to seedlings in about three weeks. Make sure they get plenty of light at this point if indoors. The seedlings should have two or more pairs of true leaves before they are transplanted outdoors.
When they’re ready for transplanting, harden off your seedlings by putting the seed trays outside in a sheltered area for about a week. Plant them in the flower bed with a spacing of at least 18 inches (46 cm.) between each one. Delphinium is a heavy feeder so it’s a good idea to add compost to the soil before putting in the seedlings.