The Stately, Spectacular Delphinium
Question: I saw some beautiful tall flowers in a garden recently. I was told that they’re delphiniums. Can you give me some planting advice for them?
B.P., Santa Ana
Answer: Often towering above other plants, delphiniums are tall, stately flowers that deserve a place in many gardens. They grow from 3 feet to as high as 7 feet and are best placed at the rear of borders.
Four or five of them create a stunning display.
Though they are often associated with blue flowers, delphiniums also come in white, shades of red, pink, lavender, purple and yellow. Leaves are generally fan-like or lobed.
You will often find giant ‘Pacific Strain’ delphiniums, which grow tall, and shorter dwarf strains, which generally grow 3 to 4 feet and sometimes shorter. The dwarf varieties do well in containers.
Although they are perennials, delphiniums are often grown as annuals in Southern California and replaced every year. They are easy to grow from seed, but at this time of year, use plants from the nursery. Plant seeds in July or August and set out transplants in October.
Plant in rich, well-draining soil in full sun. If necessary, amend with bagged compost at a rate of 50%. Do not cover the plant’s crown when planting.
Delphiniums require constant moisture. You can save yourself some watering by using water-storing soil polymers when planting. These store water and release it to the plant as needed. Follow package directions and make sure to moisten the polymers before planting, as they expand quite a bit when wet.
Avoid overhead watering, which weighs down the flower heads and may lead to mildew.
To produce such magnificent blooms, delphiniums need plenty of food. Try slow-release fertilizer when planting, which will release nutrients to the plants for several months. Otherwise fertilize every two weeks.
If you are growing giant delphiniums, it’s important to provide them with sturdy, 6-foot-tall stakes to support the flowers so they don’t flop. Place the stakes at planting time so you don’t damage roots later on. As they grow, tie them to the stake.
When delphiniums finish blooming, cut the spikes back and leave two leaves at each plant base. Scatter an all-purpose granular fertilizer over the bed and water well. In a few weeks, they should start another bloom cycle and will flower again in late summer or early fall.
Protect from snails and slugs, which find them attractive.
Delphiniums make excellent cut flowers. For long-lasting blooms indoors, turn them upside down and fill the hollow stems with water; then plug with cotton before placing in water. Use caution around children, as delphiniums are poisonous.
Have a problem in your yard? University of California Cooperative Extension (UCCE) Master Gardeners are here to help. These trained and certified horticultural volunteers are dedicated to extending research-based, scientifically accurate information to the public about home horticulture and pest management. They are involved with a variety of outreach programs, including the UCCE Master Garden hotline, which provides answers to specific questions. You can reach the hotline at (714) 708-1646 or send e-mail to ucmastergardeners @yahoo.com. Calls and e-mail are picked up daily and are generally returned within two to three days.
