Delphinium, common name larkspur, is a hardy herbaceous perennial. This means delphiniums are tolerant of our winters, H5 hardy, (explanation of frost hardy) and in late autumn the plants die back completely to bare earth and re grow each spring.
Delphiniums are an impressive border plant with tall spires of flowers which bloom in mid-summer. I grow them; I love them, but they are hard work and definitely a red wheelbarrow plant. When growing Delphiniums, there are two areas which need particular attention slugs and support.
Delphiniums grow best in moist, fertile soil in a sheltered spot away from winds. Delphiniums fare best in summers which are cooler, hot dry summers are not ideal, which can exacerbate their tendency towards powdery mildew. Although Delphiniums need sun, they are best not planted in garden hot spot for which reason planting in an area which gets morning sun is ideal.
Adding plenty of organic matter or compost worked into the planting area will help to hold in moisture and also a mulch to retain moisture. Plant delphiniums level with the existing soil, i.e. not too deep. Delphiniums have hollow stems which support the heavy flower heads, and these stems are prone to snapping if there are gusty winds and rain. In good growing conditions and summer weather, Delphiniums can look just fabulous.
Much gardening advice says to water and feed during the growing season. If the soil is reasonable, I find you can get away with not feeding them. Delphiniums will benefit from feeding if time allows, bloom well without being cosseted. Whilst summer feeding may not be essential, staking is. Which means if you don't have time to feed and stake Delphiniums, the more important task is to stake them so the plant and blooms supported.
After flowering, it is best to dead head the flower spike, and further smaller flower shoots should appear. Bees are attracted to Delphiniums drawn in part by their lovely strong blue, as bees do love blue flowers. Delphiniums are a red wheelbarrow plant as they need attention in terms of slug protection, staking and, if time allows, feeding, as detailed below. If Delphiniums are not your first choice to plant, check out summer flowering plants, scented plants, and climbing plants for more ideas on what to plant in the garden.