It's around this time of year when delphiniums begin to stand tall and proud as they bloom amongst our borders. With their vibrant colours and bold heights, these are certainly a flower we look forward to seeing every year.
We asked Chief Horticultural Advisor from RHS Wisley, Guy Barter, to share his top care tips.
Growing and planting…
- There are two ways to begin your delphinium journey - through seed raising and through propagation by cutting.
- Barter prefers cutting a shoot in spring as opposed to raising seeds every time as this is more likely to result in beautiful, tall flowers.
- If you prefer to plant seeds, make sure they are fresh - Delphinium Societies are a great place to purchase.
- For optimal results, it is best to grow them like cabbages and have a dedicated patch with very fertile (slightly alkaline) soil, lots of sun and water.
- It is very important to keep delphiniums constantly moist and not to let the plant dry out - this could cause mildew to grow which can ruin the plant.
As they grow...
- Support delphiniums with canes as they grow tall.
- They are very heavy feeders and require a lot of nutrients. At the start of the season, use mulch with manure to help keep them nourished.
- Thinning is very important for the plant's health. A newly planted one-year-old should have one spike, two-year-olds should have three spikes and an eight-year-old can have anywhere from 20 to 50 spikes.
Slugs are a major problem for delphiniums. To find out how best to deter slugs, read our guide.
Barter recommends performing a garlic drench. You can either purchase this or make your own by boiling two pints of water and adding crushed garlic cloves. Boil for half an hour and then strain into a bottle. Keep the liquid in a cool place and add two teaspoons to a gallon of water and use to water the plants once a week.
To prevent powdery mildew from ailing the plants - a common problem in dry years - try planting them widely and thinning out the shoots as they emerge from the crowns early on.
Once your delphiniums have finished flowering, cut them to ground level and give them a sprinkling of fertiliser to help them grow healthily the following year. Continue this process for some years and they will blossom annually until they eventually get too tired.