Where you can grow Delphiniums

Where Can I Grow Delphiniums?

Generally delphiniums grow well in zones 3-8. Plant Maps has extensive hardiness maps for the world. We have compiled a map, which is a rough guide to regions likely to be suitable for growing our delphiniums, using climate and natural vegetation data, weather maps and personal reports. The map is a general indication only and there will be considerable local variation.


New Millennium Delphiniums are very cold hardy. They are grown without trouble in temperature ranges of –40°C to +30°C. Winter mulching benefits here and folk often use pine branches to provide a loose protection from severe frosts. We have a report of them going rampant in South East Alaska, growing to two stories high and being tended through the upper level bedroom window. This is unusual however. They grow magnificently throughout Russia too.

People who grow delphinium successfully where summers get very hot (95°F+) all use some sort of shading to protect the plants from the worst heat of the day. This shading usually takes the form of trees which cast a shadow over the plants. The tree could be quite loose leafed. Adjacent trees help cool the ground too. If growing as annuals, plant at the end of summer and flower before the heat of the following summer.


Ideally, you should also water deeply every two or three days during hot weather (some even daily) and maybe once a week at other times. However: Never let delphiniums get either bogged or dried out, particularly when growing well and keep only barely moist immediately after cutting down after the first summer flowering or they may rot. Increase water as the plants grow back. Be sure the soil is moist going into a hot spell.

In areas coloured terracotta New Millennium Delphiniums may be grown as an annual, or at best a short lived perennial. In these areas the plants must definitely receive afternoon summer shade and efforts be made to keep the roots cool (straw mulch etc). This should be quite thick, maybe three or four inches deep or greater if very loose (like straw). The mulch helps to keep the roots moist and cool.

Avoid growing our delphiniums in the yellow areas unless you have an air-conditioned conservatory -where they will likely thrive.