Often delphiniums are thought of as
difficult and time consuming to grow. This is not the case.
While like all plants they thrive in ideal conditions, a few
basic growing techniques will ensure quality spikes in most
Soil: Delphiniums prosper in most
soil types. Amend the soil with compost before planting. Do not
allow waterlogged soil as this will promote crown rot. If
necessary, raise the bed slightly.
Transplanting: Delphiniums do not
like to be disturbed but if necessary move only young plants and
very early in the spring, just as they begin to grow.
Thinning: As the plants mature, if
they produce many stems, the weak ones should be cut off close
to the ground in early spring. The remaining stems will grow
stronger and produce a better display.
Watering needs to be consistent,
especially during the growing season. Delphiniums are shallow
rooted but a good soaking once a week should suffice for mature
plants. We are on a hill with south exposure and rely on well
water, so our watering is minimal. Mulch may be beneficial but
not directly on the crowns.
After flowering cut off the spikes
but leave the foliage until new growth starts at the base of the
plant, to promote strong roots. You may be rewarded in the
autumn with a second flowering but the spikes likely won’t be as
tall as in July.
Winter care: Cut off plant material
and clear the beds of debris before the winter, to reduce the
possibility of slug damage. Our Delphiniums are very hardy and
do not require winter mulch. They enjoy a good snow cover, if
Mother Nature provides it in your area.
Slug and Snail Control: A thin layer of coarse gritty
sand will help discourage these pests year round but be sure it
has an open texture and will not form a crust which would affect
new growth. Eliminate as many pests as possible by handpicking.
Evenings or early mornings are usually most productive for both
slugs and snails. In late autumn, cut the stems and foliage of
delphiniums to the ground. Remove all leaves, debris and weeds
from around the plants as slugs and snails winter over in these.
If your garden is heavily infested with slugs and snails, late
winter and early spring may be times of excessive damage. A
solution of aluminum sulphate (usually 2 oz. mixed in one gallon
of water is enough for 4 plants) may be sprayed over the area of
dormant delphiniums during the winter. Follow the manufacturer's
instructions for recommended strengths. This solution is
astringent and therefore is able to kill adult slugs and snails
as well as their eggs. Care must be taken to never spray a plant
drown directly unless it is dormant. Aluminum sulphate is a soil
acidifier so over use will change your soil pH and may require
an application of lime in the spring.