Where can I grow delphiniums in Australia?

There are no regions in Australia that are too cold to grow delphiniums. The limiting factor to growth is heat. As we have been unable to locate a heat zone map of Australia we have used data and opinion from a number of sources to produce a map that may be used as a guide. Local conditions will play a large part in determining how perennial our delphiniums will be but I believe the areas coloured green will generally be suitable for growing our delphiniums at least as a short lived (three years or so) perennial, and longer where conditions are relatively cool in summer.

Ideally they should not be subjected to temperatures in excess of 80degF for long periods. However, we have found both from our own experience of growing in hot houses and from the experience of gardeners in the USA and Canada, that our New Millennium Delphiniums will perform well where temperatures reach 86degF for an average of no more than 45 days during the summer. These general areas are coloured green on the map. Best results are obtained where care has been taken to provide shade, or dappled shade from the hottest summer sun and if this is done our delphiniums should be truly perennial, lasting several years.

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). Nonetheless, good management can still be rewarded with fine blooms. See growing information.

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