Delphinium plants can be either hardy or half hardy perennials.
Delphinium are very variable in height depending on the variety and can grow from anything from 15 cm to over 2 metres in height.
They bloom with tall spires with flowers of blue, pink, purple, yellow or white.
The timing of flowering is variable between species of Delphinium, and can be anything from the end of spring to autumn.
Tall Delphiniums photograph by cacophonyx.
Larkspurs - Delphinium, Huntington Library Gardens by DominusVobiscum.
When growing Delphinium outdoors from seed they should be sown either at the beginning of spring or the beginning of autumn; simply cover the seeds with topsoil.
The spacing will depend upon the variety (small species about 40 cm apart; large ones about 80 cm apart). They can grow in either a sunny or lightly shaded area of the garden that has good drainage.
The soil should be rich, deep and have a slightly acidic to neutral pH of 5.5 to 7.
Once growing Delphinium should be fed with fertilizer at the beginning of spring.
Taller varieties of Delphinium should be staked.
As soon as the first bloom is over the flowers should be cut off; this will result in further growth; once the new growth has reached about 20 cm then the old growth should be pruned off.
If you require more Delphinium plants then they can be propagated by division; this can be carried out in the spring.
I hope that you enjoyed this guide on how to grow Delphinium plants. Updated September 2020.