Gardening Articles: Flowers :: Perennials
Delightful Delphiniums (page 2 of 3)
by Charlie Nardozzi
Many Sizes, Stately to Compact
Unlike their relatives the larkspurs (Consolida), delphiniums are true perennials. Most delphinium varieties are listed as hardy to USDA Hardiness Zones 3 through 8, but they thrive best in zones 3 through 6 or in cool-summer areas of zones 7 and 8. The tall hybrids are the most sensitive to heat (days consistently in the 90s), but they can be grown in warm areas if planted in fall and treated as annuals. However, heat causes the flower stems to be shorter. Many of these hybrids were developed from seed, so actual flower colors may vary slightly. Let's look at some popular varieties grouped by their heights.
Tall (4 to 6 feet). English hybrids are probably the most dramatic of all the delphiniums. They come in a range of colors, and produce two or three flower spikes per plant the first year, twice as many in subsequent years.
The best known of the tall hybrids is Pacific Giants (also sold as Round Table series), with dense, heavy spikes of 3-inch-diameter double flowers that require staking. Two of the most stunning varieties are 'King Arthur', with royal violet flowers and a contrasting white bee (a cluster of short petals in the center of each flower); and 'Black Knight', with a dark violet blue flower and a black bee. Although most hybrid delphiniums are blue, pink, violet, or white, 'Beverly Hills' offers scarlet red flowers on 4- to 5-foot-tall plants.
The newest delphinium varieties come from New Zealand, where Dowdeswell's Delphiniums has developed the New Millennium hybrids. These plants compare favorably to Pacific Giants but are hardier and have stronger spikes, more petals per flower, a broader color range, and better disease resistance and heat tolerance. Varieties include pink 'Blushing Brides' and purple 'Royal Aspirations'. These are a good option for gardeners in warm-summer areas who want to grow the tall, large-flowered varieties.
Summer trials in New Zealand showed Pacific Giants dying out after two years from heat and disease, while the New Millennium hybrids were still going strong after four years. The last two years of the trial were conducted during summer temperatures that were consistently in the 80s and 90s.
Medium (2-1/2 to 5 feet). In this group are varieties of D. belladonna, whose 3- to 5-feet-tall loosely clustered flower spikes don't require staking. These bushier plants survive better in summer heat than taller hybrids do, and flower spikes produce six or seven stems the first year, compared to two or three on the taller kinds. 'Belladonna' features sky blue single flowers. 'Casa Blanca' is a white-flowered version of D. belladonna. 'Bellamosum' has deep blue single flowers.
Connecticut Yankee, an older mix, is particularly tolerant of hot summers; its flower spikes are a mix of blue, violet, and white flowers on 30-inch-tall stems. Magic Fountains series, a dwarf version of Pacific Giants, features the same densely clustered, large, double flowers as its parent, but on 2- to 3-foot spikes. Two of the best varieties are 'Sky Blue', with a white bee, and 'Cherry Blossom', with a pink flower and white bee. Clear Springs is a new series whose height falls between Pacific Giants and Magic Fountains; its strong spikes make excellent cut flowers.
Dwarf (2 feet or less). If you really want short delphiniums, choose from varieties that reach no more than 2 feet tall. These don't have the large flower spikes of the tall types, but the plants are better adapted to warm-summer areas.
D. grandiflorum 'Blue Butterfly' has electric blue single flowers, loosely clustered on 15-inch spikes. 'Blue Mirror' has brilliant gentian blue single flowers on 2-foot spikes. Both can bloom all summer in zones 3 through 6.
Two other delphinium species are shorter lived and harder to grow, but feature unusual flower colors for delphiniums. D. zalil features compact plants with deeply cut foliage and single yellow flowers on 2-foot spikes, and D. cardinale, a California native, features red spurred flowers on 2-foot spikes.