Delphinium hybrids are among the most dazzling and dramatic flowers that can be grown in your garden. Their tall flower spikes add vertical accent in some amazing shades and make stunning cut flowers. The blues are particularly magnificent.
Modern hybrids also include shades of pink, purple, lavender, white and yellow as well as many beautiful mixed combinations. New introductions in Northern hemisphere include bright red, gold and orange hybrids!
The origin of delphiniums appears to be a series of cross pollinations between several European and Siberian larkspurs. Hundreds of hybrid strains have resulted from 1m dwarfs to 4m giants. The English Wrexham hybrids and (U.S.A) Pacific Coast Giants are among the best known. New Millennium and F1 N.Z. Hybrids are superior for New Zealand's climate.
These are cool weather plants that can withstand winter freezing much better than subtropical heat and humidity. They enjoy a cool root run in an organically rich, slightly alkaline, moist soil that drains well. Deeply dug (to60cm), fluffy soils free of overcrowding roots provide ideal conditions for their root system to spread.
They love the sun, producing their most robust spikes in open locations sheltered from winds not deeply shaded by trees or crowded by other plantings. In subtropical climates provide at least some midday or afternoon shade from scalding sun.
Delphinium does very well in large containers and tubs as well as within congested garden borders but spikes will be smaller. Some varieties will flower, although not as well, in light shade.
Staking is very important from the time spikes develop. Young bud spikes are often brittle in cool, wet conditions. Fully developed flower heads become very heavy if laden with rain and whipped about by winds. Stake securely below and within the spike.
Late summer and autumn are good times to plant delphinium seed. Lightly cover the seed with a fine potting mix in flats or small pots. Keep moist, sheltered, partly shaded and guarded from snails. Seedlings will be ready for planting next spring or autumn. Some varieties will flower next summer but most will be at their best the year after.
For those looking for more immediate results, autumn is the ideal time to establish advanced seedlings and young (first year) crowns. These can be purchased for a few dollars from a specialist grower. Transplanting into permanent positions now insures the plants will be well established for a spectacular display from late spring to autumn.
Plant crown at ground level. Crown can be slightly higher in wet situations. Where severe freezing could be a problem plant a little deeper and provide a winter mulch. Water by flooding the ground rather than overhead. This is especially important as flower spikes develop.
When in active growth feed around the plant with a well balanced commercial plant food mixed with blood and bone and compost. Add a little dolomite lime when feeding into acid soil. Spread this mix lightly and evenly around the plant taking care to avoid burning by not letting this contact the crown or flowering cane.
Once the first bloom fades remove it to the top leaf and smaller spikes will quickly develop. As these finish cut the cane back to just leaves until new growth appears at the base then remove the old cane entirely. The new growth will produce flowers for late summer and autumn.
When growth fades in autumn cut the plant back severely in readiness for winter dormancy. Advanced crowns can be divided then. Be sure to mark the spot as plants sometimes die away completely for a few months.
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