How To Grow Delphiniums
Delphiniums are hardy from zone 3-8. That covers most of the United States except for the warmest areas of the country. We think the real secret for growing Delphiniums reliably is to remember that they are heavy feeders.
Prepare your planting spot by turning the spot with a shovel as deeply as you can. Add as much compost as you can and this will make your delphiniums all the more magnificent. A little lime or wood ash is also beneficial if you know your soil is acidic. They like the soil pH to be neutral.
If you live on the warmer side of their range (heat and humidity are hard on them), you may want to allow some shade to fall on them during the day and mulch them to keep the roots cooler and consistently moist (not too wet or dry). Mulching in winter is not necessary but if you live in an area with little snowfall and the ground is subject to extreme heaving this will protect the dormant plant.
The tall varieties can get up to 6 Ft.! These are the ones that need staking. Tall bamboo rods are sold at most garden centers and they are not very expensive. The green ones blend in quite well.
In summary, How to grow Delphiniums:
- Plant in spring by preparing the ground well and digging the spot deep with a shovel.
- Add as much compost as you can for additional fertility.
- Spreading lime or wood ash in the soil is helpful if your soil is acidic.
- In warmer or drier conditions, give delphiniums part shade.
- Stake the tallest varieties.