Summer hyssop or Korean mints are the current darlings of the garden, producing spires of tubular flowers in predominantly blue and lilac, but also increasingly in pastel shades of apricot, red, pink, and yellow. They range from being herbaceous perennials to those with a woody rootstock, producing a sheaf of fresh shoots each year.
In garden terms agastache, meaning 'many spikes', spans around 10 species with slightly different habits, some upright, others more tufted and slender-shooted. Like many members of the mint family, they've aromatic foliage, spanning peppermint through to aniseed. There are two main groups which accounts for the differences in habit and flower colour. All are very attractive to pollinators, especially bees and butterflies.
Although none are bone hardy, those from North America and Asia, such as A. foeniculum and A. rugosa are more robust and upright, with spires of flowers in shades of blue and white and should survive most winters. The smaller, shrubbier, more colourful types, such as A. aurantiaca and A. cana, come from Southern USA into Mexico and range from being tender to semi-hardy.
Agastache are easily grown in well-drained soil in a sunny, but not too dry position or in pots. Hardiness is improved by not letting them get waterlogged in winter. Tender species and varieties may survive mild winters, but can be protected as rooted cutting in the greenhouse or raised from seed or plug plants each year.