How to grow delphiniums

Fast facts about growing delphiniums

How to grow delphiniums

Step 1

Choose a spot in the garden that receives regular full sun (no shorter than 3 hours of direct sunlight).

Step 2

Add in a compost fertiliser or a potting mix that is high in potassium.

Step 3

Sow delphinium seeds directly into the ground. Lightly cover with soil and press down.

Step 4

Water generously.

Step 5

Cover with a newspaper, or pieces of cardboard so seeds are not overexposed to the sun. This is only until the seed is established and grows about 5cm above ground.

Step 6

Once established, feed every week or so with a high potash fertiliser.

How to prune and maintain delphiniums

Delphiniums are short-lived perennials. In their first spring, they send up spikes with several shoots.

Thin back to one or two shoots per stalk, then three or four shoots in their second year and five to eight shoots in their fourth year, when they reach their peak.

They bloom all summer long and you can keep them blooming longer by deadheading spent flower spikes back to small flowering side shoots and, when blooming has finished, cut stalks to the ground.

New, smaller flower stalks will develop that will survive light autumn frosts.

Do delphiniums spread?

Delphiniums are prone to spreading and do not like competing for space with other plants. Because of this, it is best to plant is spread out areas, and alleviate overcrowding by thinning them out.

Do delphiniums need a trellis?

Delphiniums do not usually need a trellis, however, they do grow best when supported with a stake. This is because the stem of a delphinium is actually hollow, which means it can easily fall over or break in the wind.

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