Growing Delphiniums
Planting
Choose a site which is not waterlogged during the winter. Water your
plant well and prepare the ground thoroughly by incorporating organic
matter or compost. Plant at the correct depth so that the compost is level
with soil. Firm the plant in securely so that the roots can e
stablish
quickly. Water in well and try not water the leaves if possible. Delphiniums
grow in most soils but need plenty of food and moisture to perform well
so make sure you water regularly until the plant is established.
Flowering
Delphiniums usually flower May to July but young plants often have their first flowering in late summer, after their roots have established. After flowering cut the spike down to the level of the foliage. This stops the plant setting seed and directs its energy to the roots.
Staking & Tying
This may be necessary on a windy site and with larger varieties. It is best to start when plants are still small and use a square or triangle of 120cm (4ft) canes close to the plant and tied together with twine. Place the canes 30cm (1ft) in the ground taking care not to damage the crown or the roots of the plant. This allows the spikes some movement. Birch twigs can also be used successfully and are less obtrusive. Start tying the plant at about 15cm or 6 inches with the final tie just below the florets. Tie firmly but not too tightly and always allow the plant some movement so that spikes do not snap in the wind.
Over Wintering
Once the foliage has died back in the autumn stems can be cut down to ground level and all staking removed. On wet soils particularly slugs and snails will over winter near plants and eat the fresh shoots as they appear. These must be controlled with slug pellets or a range of other methods.
Spring Treatment
New growth should appear in Spring and as soon as this appears plants can be fed with a good balanced compound fertiliser such as blood fish and bone meal. Keep a sharp eye out for slug and snails at the time!
Problems
Apart from protecting your plant from slugs and snails there are few problems with Delphiniums. Mildew (a grey mould on the foliage or flowers) can cause concern in humid weather when plants dry out. To guard against this you can make sure your plant does not get too dry and spray with a fungicide early in the season, then as per manufacturer’s instructions.