How to Grow Delphiniums
These Stately Plants are Worth the Effort
No other flower is as coveted for the home garden as the majestic delphinium, and with good reason. It can be one of the trickiest perennials to grow. While some gardeners have great results, with tall, strong plants, many of us end up with spindly, weak stalks with few flowers. What do they know that the rest of us don't?
The Right Climate
Delphiniums prefer cool, moist weather. While they love the sun, they will wilt and die in extremely hot weather. They will not tolerate wet soil, but will not survive drought either. The climates of England, the Pacific Northwest, and the coast of Maine are much to their liking. In areas of intense heat they may grow if they are provided afternoon shade. In cooler spots they are more apt to thrive in full sun.
Ideal Soil Conditions
Anyone who has successfully grown delphiniums knows that they need a humus rich, slightly alkaline soil that has been dug and loosened deeply. They will not grow in poor soil. Compost should be added now and then, as should bone meal, limestone or wood ashes, to sweeten the soil. Fertilizer can be added in the spring and summer.
Prevent Disease and Insect Damage
These plants are prone to certain problems, particularly fungal diseases and crown rots. Giving them plenty of growing room will help to prevent these, by allowing air to circulate around the base of the plants. Mites and slugs adore delphiniums, so the use of insecticides may become necessary. Mixing sulfur dust with rotenone powder and dusting on the leaves every few weeks throughout the summer will help to deter these diseases and insects, especially in humid weather.
A Few Tips
Most varieties of delphinium grow quite tall, with some, like d. elatum, reaching as high as six feet. These should all be securely staked. This helps to prevent them from toppling over as they grow. They should also be protected from wind, as the top heavy flower stalks blow over very easily. Other varieties such as d. belladonna and d. grandiflorum are much shorter and do not need to be staked. They are not as showy as the taller varieties, but tend to be much easier to grow, and they are hardier.
After the first bloom is over, cutting flower stalks off at the base will help to persuade them to re-bloom. Watering well with fish emulsion at this time will also encourage them to flower again. Delphiniums will need a thick covering of mulch in the winter. Even with this protection, many will not survive a hard winter. Those that do make it will most likely not live through a second winter. Therefore, many experienced gardeners treat the perennial delphinium as a biennial, replanting them every two years. This ensures that there will be a few of these beauties in the garden every year.
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