Delphiniums Thrive with Pampering
Growing English delphiniums takes a little more effort than sticking them in the ground and watching them grow. But if you follow these suggestions, you’ll end up with plants you won’t believe.
– Plant in well-drained, friable soil amended with organic material. Raised bed is ideal. They don’t like to be waterlogged.
– Site in full sun and protect from wind. Avoid placing plants under large trees or tall hedges, which compete for water. Be choosy about where you put them; they don’t like to be moved.
– Plant in groups of threes, at least 2 feet apart for regular English delphiniums, 18 inches apart for dwarf varieties. Add two large handfuls of bonemeal to each planting hole, mixing in well. Tap plant out of pot and wake up roots by gently pulling them apart with your fingers. Position plant so that it is at the same depth as it was in the pot. Firm in well so that plant stands securely. Water in well and continue watering every day until seedlings are well-established.
– When new growth reaches 2 inches high, scratch in a balanced fertilizer (12-12-12) according to package directions. Or, feed with a mixture of 2 tablespoons ammonium sulfate and 1 cup bonemeal, lightly scratched in around each plant. Water in well.
– Slugs love succulent new growth. Hand-pick or bait in spring.
– Thinning is essential for vigorous plants. When spring growth is 2 to 3 inches high, select strongest shoots (one for newly planted seedlings; three for second-year plants; five for older plants). Cut off all others at ground level.
– Protected from strong wind, dwarfs should stand without staking; otherwise, it’s best to stake them when they get 9-12 inches high. Insert four thin, green bamboo canes (about 4 feet tall) into the ground, forming a square around the plant (three in a triangle can work, too). Tie twine tightly to the canes 10-12 inches from the ground. Tie a second strip of twine a bit looser to just below the first bottom floret.
– Don’t let plants dry out. Mulching with compost or well-rotted manure helps conserve moisture.
– After flowering, cut spent flower spike directly under lowest floret. When stems and remaining foliage turn brown, cut them off at ground level. You’ll get a second bloom about 12 inches high. Cutting down before it browns will shorten its life.
– When plants die down and become dormant in fall, cut stems at ground level. Remove leaves, debris, stakes and weeds around plants to eliminate hiding places for pests. Gently remove some of the soil around crown and cover with coarse gritty sand to keep slugs away. Cover cut-off hollow stems with a small piece of aluminum foil to keep water out and avoid crown rot.
– To make more plants, take what’s called an Irishman’s cutting when thinning: As you cut down unwanted shoots, scoop a little of the crown with it and use as a cutting. Or, wait till flowering is over, cut the whole plant back and wait a few weeks. When shoots start coming up, scoop up and use as cuttings.
To learn more
For an annual yearbook, access to the handbook “Simply Delphiniums” ($6) and a free package of English delphinium seeds, join The Delphinium Society of Great Britain by sending your name, address and $10 in cash (to avoid conversion charges) to Shirley E. Bassett, “Summerfield,” Church Road, Biddestone, Chippenham, Wiltshire SN14 7DP, United Kingdom.
Reprinted from the Oregonian’s Home and Garden section, March 22, 2001.