Delphiniums

Nothing quite beats the drama of delphinium flowers. In June and July, they produce towering flower spikes that can reach over 2m tall. They’re probably best known for their vivid sapphire blue flowers, but they also come in mauve, pink, white and even red. Delphinum flowers can be single or double, depending on the variety.

Delphiniums are a cottage garden and herbaceous border staple, bringing height and colour to displays and mixing well with roses, peonies and other vertical flowers such as lupins and verbascums. The flowers are loved by bees and look stunning in a vase.

Delphiniums are in the buttercup family (Ranunculaceae) and have been grown in the UK for centuries. The word delphinium comes from the Greek delphinos, meaning dolphin, probably because of the shape of the opening flowers. Their common name, larkspur, dates back to Tudor times.

Most delphiniums are hardy perennials, but annual and biennial varieties are also available. The Elatum Group of delphiniums are the most commonly grown and are the tallest type, with spikes of single or double flowers reaching up to 2m. Belladonna delphiniums are shorter, with a looser, more branching habit and single flowers. ‘Pacific Hybrids’ were developed in the 1950s and 1960s, and are short-lived perennials or biennials. They look similar to ‘Elatum’ delphiniums but are shorter. The ‘Magic Fountain’ series of delphiniums are short and more compact, suitable for smaller gardens.

Delphiniums need care to keep them looking good. They need protecting from slugs in spring, staking, moist soil and plenty of feeding. If you cut them down to the ground after flowering, you may be rewarded with a second flush of flowers in September.

How to grow delphiniums

Grow delphiniums in moist but well-drained soil in full sun. Delphiniums struggle in wet winter soil, so aid drainage by adding grit to the planting hole if you have heavy soil. Protect emerging shoots from slugs in spring and stake as soon as they start to grow. Feed weekly with a high potash fertiliser. After flowering, cut stems back to encourage a second flush of blooms. Mulch in autumn with well-rotted manure or leaf mould.

More on growing delphiniums:

For best results grow delphiniums in moist but well-drained soil in full sun. Delphiniums are tall plants, so do best at the back of a sunny border. Avoid windy spots, as wind can blow the plants over.

How to plant delphiniums

You can plant a delphinium at any of time of year, but spring or autumn is best as the soil will be warm and moist. Dig a planting hole and add compost or well-rotted manure in the bottom, for a nutritious boost. Delphiniums struggle in winter wet, so add grit to heavy soils to aid drainage. Plant your delphinium at the same depth it was growing in the pot, and back-fill with soil, firming in gently. Water in well.

How to care for delphiniums

Delphiniums are hungry plants, which means that they need feeding regularly. Apply a liquid fertiliser every couple of weeks once the first shoots appear to encourage strong growth.

Spring is also the best time to stake taller varieties, either with canes or using a frame that plants can grow up through. Delphiniums thrive in cooler temperatures, with slightly moist soil in summer, so make sure plants don’t dry out in hot weather.

Although they have a relatively short flowering season, cutting delphinium flower spikes back as soon as they have faded can encourage plants to produce a few flowers in late August or September.

To cut back a delphinium:

As soon as the flower spikes starts to look tatty, cut every flowered stem right down to the ground, leaving any developing side shoots, and the remaining foliage at the base then water the plant well.

In autumn, once the plant has finished flowering, cut the plant back down to the ground.

To keep plants flowering well, you can divide them every few years, in spring.

Source: https://www.gardenersworld.com/how-to/grow-plants/how-to-grow-delphiniums/