How to grow Delphiniums
How to grow Delphiniums
Delphiniums are an impressive border plant with tall stunning blue spires which bloom in mid summer. I grow them, I love them, but they are hard work and definitely a red wheelbarrow plant. Delphiniums are a hardy herbaceous perennial, which means they are tolerant of our winters hardy down to H5, (for explanation of plant hardiness.) In late autumn and winter they die back completely to bare earth and re grow each spring. Delphiniums come in lovely shades of blue, white, pink and purple, often with a contrasting eye or 'bee' . Tall Delphiniums look fantastic at the back of a border, although there are also more compact varieties which being smaller need less staking but still need to be supported. I try and use twigs and branches pruned off plants during the year to create more natural looking plant supports. ( check out plant supports for free)
Delphiniums need slug protection. Unfortunately slugs are fond of Delphiniums, especially keen on the new tender shoots in the spring and you need to lay down slug protection. There are lots of ways to defeat slugs.
Delphiniums need to be planted in full sun and fertile soil, which is moist, but well drained and most importantly, sheltered from strong winds. Much gardening advice says to water and feed during the growing season; I find if your soil is reasonable that is not really necessary and all the images above were grown without additional summer feeding, it all depends on the amount of time you have available. Delphiniums are hungry feeders, and will definitely benefit from feeding if time allows, but will bloom well without being cossetted. Feeding is said to improve the prospects of a second crop later in the year.
In the 1st and 2nd images above Delphiniums are is growing alongside Thalictrum which is a great combination; the tall with fluffy flower heads Thalictrum combines well in mauve and contrasts in white.
Tips on Growing Delphiniums
Delphiniums need attention especially when first emerging as slugs love their tender new shoots. In a previous garden where the slug population was very high, it was nearly impossible to grow Delphiniums, because the slugs ravaged them before they got established.
All Delphiniums need staking as soon as they start to grow above 30 cms and they need plenty of support. The flower heads can be damaged by heavy summer rain or storms, when the blooms become heavy with the rain water and it is hard to stake them enough to prevent the stems from snapping, especially if there are high winds. This is one of the reasons for the recommendation to plant in a spot sheltered from high winds. Delphiniums bloom best in summers which are calmer with less rain.
Check the variety carefully as many Delphiniums can get very tall. I have a clump of the Pacific variety which have been established for about 5 years which are now well over 5ft /1.5m. The colour range is traditionally blue, pink, mauve there are now some yellow Delphiniums and a greater range of colours.
Good Types of Delphiniums to Grow
There are a number of RHS merit Delphiniums which are good to grow and worth checking out: D. Giotto a lovely two tones blue/mauve flowers growing up to 1.5m; D.'Bruce' deep violet purple reaching up to 2.5m , D.'Blue Dawn' pale blue, very tall as well. Good pink varieties worth checking out are D. elatum 'Sweethearts' (New Millennium Series) tall up to 2.5m; and D.'Rosemary Brock' smaller variety 1.5m with strong black "bee" centre to the flowers. There are many white varieties also with RHS merit such as D. Sandpiper which is white with a black bee and smaller up to 1.2m.
There are also a magic fountain series of Delphinium which are more compact in shades of blue violet and white up to .5m. In addition there are several such as D. (Belladona Group) Atlantis which are strong blue and D. "Atholl" white which are both around a metre.
After flowering dead head the flower spike, and further smaller flower shoots should appear.
Bees are attracted to Delphiniums drawn in part by the their lovely strong blue, as bees do love blue flowers, illustrated left.
How to Grow Delphiniums from Seed
Delphiniums are surprisingly easy to raise from seed and some varieties will flower the first year. Delphiniums plants are quite expensive to buy and it is worth trying to grow them from seed as they germinate easily and grow quickly into sturdy plants. Simply sprinkle the seed into small pots or a seed tray, cover with a little compost and spray to dampen. Either place in a propagator or make a small propagator by covering with a plastic bag held in place by an elastic band. The creates a better environment for germination. As soon as the seedlings are established take out of the propagator and grow on in a sheltered spot, ideally a greenhouse. Check to make sure the compost does not dry out and pot on into individual small pots and then into a larger pot. Once the risk of frost has passed and the plant is of a reasonable size, plant out and protect from slugs. Once established Delphinium will come back reliably each year and the main chore is extensive staking at the beginning of the season which is essential.