Delightful Delphinium

Nothing says summer in a cool-climate garden quite like the tall spires of Delphinium elatum. I included delphinium early in my gardening efforts here, but my early attempts to grow these plants were those of a serial delphinium killer. I would buy a delphinium in bud from a local nursery and stick it in the ground. The delphinium would grow and bloom and look beautiful, and then it would disappear. The next year, I would go out and buy another one and do the same thing all over again. Occasionally, one would come back a second year, but that was rare. Eventually I learned something about what these plants needed to thrive (rich, moist, sweet, well-drained soil), realized that (except for the well-drained part) I wasn’t providing any of that, and stopped trying to grow them.

I didn’t give up my desire for delphinium, though, and when I began to plan the blue and yellow border in the back garden, I decided to make an extra effort to create a hospitable home for these plants. This flower bed is fairly large, and I set aside an area of about 40 square feet for delphinium. There, I dug in extra manure for richer soil and an extra measure of wood ash to sweeten my acidic soil.

Unlike the vegetative propagation typical of most perennial cultivars, delphinium varieties are usually grown from seed and identified by their seed “strains.” My early delphinium growing attempts were with the strain most widely available in the United States at that time, the Pacific Giant varieties, which were bred in the Pacific northwest and particularly well suited to that climate. By the time I was ready to try delphinium again in 2004, I found that my local nursery no longer offered the Pacific Giants, but was instead growing and selling the New Millennium strain developed in New Zealand by Dowdeswell’s Delphiniums. Like other delphiniums, these come in a lovely array of colors in the blue-violet-pink range. I currently have four different varieties growing in my garden: ‘Double Innocence,’ ‘Blue Lace,’ ‘Royal Aspirations’ and ‘Pagan Purple.’ Not only are the delphinium spires a stunning presence in the garden, but the individual flowers are also beautiful.

I am enthralled by the soft mix of pastel hues in ‘Blue Lace,’

by the black “bees” at the center of ‘Royal Aspirations,’

by the Galanthus -style markings on the flowers of ‘Double Innocence,’

and by the rich mixture of blue and violet in these ‘Pagan Purple’ flowers.

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The New Millennium delphiniums have been widely hailed as being tougher, more vigorous plants than the Pacific Giants and more tolerant of heat and humidity. Dowdeswell’s rates them for USDA zones 3-8. In many climates, if they are deadheaded after the first bloom, they will send up new growth and produce a new set of flowers later in the season.

Like all delphinium, however, these are not carefree garden plants. Delphinium tend to be relatively short-lived and seldom survive more than five years. They are also heavy feeders; I find they are more likely to thrive if I fertilize them twice each season, once in spring and once when the second flush of growth begins. Donna and Steve Palmer at Plainview Farm, where I buy mine, recommend limiting the number of flower stems in the first years as the plants are getting established. Their formula is to allow only two stems to develop in the first year, three stems in the second year, four stems in the third year, etc., and never more than five stems on a single plant. Allan Becker recommends dividing the plants every three years.

Delphinium are probably not a good choice for gardeners who hate to have stakes showing in their gardens; because these plants absolutely must be staked. The blooming inflorescences alone are typically 30-36” tall, and that is on top of stems averaging more than 3’.  I use one sturdy 6’ bamboo stake for each 1-2 delphinium stems. It is important that the stake be strong enough to support the weight of the fully blooming spire and that it be long enough so that, after about 1’ is sunk in the ground, the stake is still tall enough to reach the lower part of the inflorescence. I tie each stem to the stake at several points along its length, with the top tie in the bottom part of the inflorescence.

If, despite my best efforts, I look out after a heavy rain to find a bent stem and a delphinium spire pointing at the ground, I go out with a pair of scissors, cut the stem, and bring the blooming delphinium in as a cut flower for the house. Because, whether inside or out, delphiniums are delightful.