Delphiniums – who hasn’t seen these glorious flowers and wanted more for their own garden?
They are truly the monarch of perennials.
Delphiniums spp. are thick-stemmed and up to six feet tall. Their sturdy stalks are covered with divided, maple-like leaves.
Each flower has five petal-like sepals in shades of blue, purple, white or pink, the top one bearing a curved spur. In the center are two or four fuzzy true petals that give the flowers a ‘bee’ look.
Most cultivated delphiniums are hybrids, with Delphinium elatum as their parent.
Natives of high, cool and moist areas, delphiniums do not like hot summers and dry soils. They need lots of nutrients to build their towering blooms. So dig the soil deep and loose with lots of compost, enough wood ashes, limestone or bone meal to sweeten it. They do not like to have wet feet. Mulch to keep their roots moist and cool.
They need at least six hours of full sun a day. Too much shade can cause the spike to grow tall, but leave bare spots. Plant them in an area sheltered from wind. If planted too deep, they can get crown rot in a wet winter.
For a nice show, plant three in a group at least two feet apart. In the spring, when they reach two inches high, apply a balanced fertilizer such as 12-12-12 according to directions. Water if there is no rain.
Thin your plants each year. Thinning encourages dense, luxurious flower spikes. Selective thinning also prevents the plant from blooming itself to death. First-year plants will have one spike, thin second-year plants to three spikes.
Older plants should have only five. The time to thin is when new growth is two to three inches high. Pick the strongest stems to stay, plus one for good measure; cut others off at ground level. The extra one you saved earlier will be cut off at staking time.
To stake, contain the stems, not the flower spike. When they are nine to twelve inches tall, place four 4-foot stakes into the ground forming a square around the plant. Take a string and bind it tightly to the stake ten to twelve inches from the ground. Make a second tie twenty four inches from the ground, (just below the first bottom floret). This allows the heavy spikes to move inside the twine without breaking. Remember, they do not like to be dry, but never water the flower heads. The extra weight can cause breakage.
After they bloom, cut off the spikes under the first bottom floret and let the leaves die naturally. If you cut too soon, before it browns, the plant can die sooner. Many time you will be rewarded with a second bloom that season.
You are able to review fact sheets at our website cceoneida.com or call our horticultural hotline at 315-736-3394 between 9 a.m. to noon on Wednesdays and Fridays.