Planting Delphiniums 

Planting Delphiniums

1. Water well before planting. 

2. Dig a hole that is slightly bigger than needed and incorporate some compost into the soil at the bottom of the hole. 

3. Take the plant out of the pot and hold it in position as you back fill with soil/compost.  Adjust the height so that the finished soil level around the plant is the same as it was in the pot. 

4. If you use granular fertiliser, sprinkle some liberally on the surface of the soil around the plant. 

5. Water the plant in and this will start to filter nutrients from the fertiliser into the rootzone of the plant. 

6. If you don’t have any granular fertiliser, put some liquid feed into the watering can when you water the plant in to give it a boost. 

Where to Plant

Delphiniums grow well in a sunny situation where the soil is free draining.  They will benefit from soil that has been enriched with compost or organic matter. We recommend supporting the plants with canes or stakes to prevent wind damage. 

Compost and Feed 

In Spring and early Summer Delphiniums are fast growing plants and benefit from regular applications of fertiliser.  Feed them well when planting with a granular or pelleted feed such as bonemeal, Growmore, Vitax Q4 or similar.  Then every couple of weeks between April and July add some liquid feed such as Miracle Gro or seaweed fertiliser (e.g. Maxicrop) into your watering can and you will find the growth is greener, stronger and more vigorous – and there will be a greater number of taller flower spikes per plant. 

Caring for Delphiniums

Delphiniums can flower twice in a season if they are treated well.  The first flowers come in early June and last for 3 or more weeks.  If they are then cut back at the base towards the end of June and given a good feed, they will shoot again from the base and flower again in August.   

Often gardeners recommend thinning out the stems when they get to about 30cm tall, favouring the best 3 or 5 stems.  This opens up the crown, reducing the tendency for a white powdery mildew to creep in and leads to stronger stemmed flowers.  

If the stems of your plants do become mildewy, spray them with the following mix:  

• One rounded tablespoon of bicarbonate of soda dissolved in half a litre of water 
• plus a couple of teaspoons of vegetable oil thoroughly shaken up together 

This should stop it in its tracks.  If not, don’t despair.  Cut the plants right back, remove all the diseased plant material, feed the plant and see it grow back again.