Delphinium
Delphinium – a sliver of sky blue
Delphinium has travelled to the Nordic countries from both Asia and North America. There are many different varieties and crosses of delphinium. Some are hardy in Sweden and are grown as perennials. Others, such as the Chinese and Roman delphinium, are grown as annuals. Many of the varieties we grow today are bred hybrids.
There are several legends about the origins of delphinium. Among North American Indians, it is said that delphiniums are actually shards of the blue sky. These shards fell down one day when a creature from the other side of the sky wanted to look at us humans. In Greek mythology, it is said that delphiniums grew from the blood of the fallen warrior Ajax.
In Sweden, delphiniums have been cultivated since the 16th century. The plant gets its name from a small growth on the flower. It resembles a spur used in horse riding.
Different ways to sow delphinium
- Propagating delphinium
Sow delphinium indoors in April-May. The light-growing seeds should only be covered with a thin layer of soil or perlite. Keep the soil surface moist during germination. Protect the seeds from drying out by using a transparent cover or plastic with air holes. Spray with water if the soil becomes dry. Delphinium seeds germinate at room temperature. Place the seedlings in a bright, cool place once they have emerged. Then they will not be gangly but will grow nice and compact. The roots of the delphinium are a little sensitive. So be careful when replanting.
- Direct sow delphinium
Delphinium can be sown directly outdoors in spring as soon as the soil is ready.
- Sow delphiniums in autumn
Delphinium can also be sown in autumn in Sept-Oct. Overwinter the seedlings outdoors in a sheltered position. Plant them the following spring in their final location. They get a jump start on the season and flower early.
Planting out delphinium
Plant out pre-grown delphinium in well-fertilised soil when the risk of night frost is over. Harden off the plants by leaving them outdoors for longer and longer periods over a few days.
Delphiniums thrive best in a sunny spot, but a semi-shady position also works well. They do not like to grow in acidic soil.
Most varieties of delphinium grow tall and need plant support. Grow them against a wall, tie up the stems with garden string or support them with a trellis, bamboo sticks or branches. Another option is to plant delphiniums together with plants that provide them with support. A well-proven combination is the co-cultivation of delphiniums with roses.
Caring for delphinium
Provide nutrient supplements when the delphiniums are in flower. Place grass cuttings or other organic material between the plants. This will keep moisture in the soil, smother the weeds and provide extra nutrition as they decompose.
Avoid powdery mildew by watering delphinium in dry weather during spring and early summer.
Remove wilted flowers to stimulate new flowering. If you want fewer and stronger stems, you can thin out the weakest ones.
Beautiful cut flower and durable everlasting
All parts of the knight’s spurge are poisonous, especially the seeds. But you can enjoy the flowers with your eyes in flower beds and bouquets. The long stems make delphinium a beautiful cut flower. The flowers are also durable to dry as an everlasting in a pastel-coloured winter bouquet.
Author: Johanna Damm
Fact-checked by Erik Hoekstra
Last updated 2022-10-14