This is one of a new series of posts based on real questions I have been asked. Feel free to add to the answers or include your ideas and experiences.
Ranunculus is a large genus, largely of herbaceous perennials, though there are alpine gems as well as some quite annoying weeds such as creeping buttercup (Ranunculus repens). Many, including the weeds, are plants of heavy, wet soils. The genus is named after ‘rana’ (frog) because of their liking for wet soils. Almost all have yellow or white flowers. A notable exception is Ranunculus asiaticus which, despite the name, is not from Asia but the eastern Mediterranean and North Africa – fairly ‘Asian’ from a European point of view, remembering that most of these early-named plants were classified and named in Western Europe. Anyway, this ranunculus, sometimes called (archaically) the turban buttercup, has long been cultivated and is now, after much selection and hybridisation, a common cut flower and, in theory, garden plant. The poppy-like flowers are available in a huge range of bright and pastel colours including purple but not blue – the same range as dahlias.
Being a Mediterranean plant it can be difficult to please in northern European gardens and has limited use. I had a question recently which showed the difficulty.
This reader was growing some indoors and they had sprouted and wanted to know when to move them to an unheated ‘mini-greenhouse.
To handle this plant successfully it pays to understand its background – as it is with most plants. It comes from Mediterranean areas so is adapted to be dry in summer, when it rests, and it grows in the mild, wet seasons from autumn, when rain starts, through winter, till spring. It comes into leaf in autumn, grows through the winter and blooms in spring, after which it rapidly dies down and remains, in summer, as fleshy, tuberous roots, often described, because of their appearance, as ‘claws’.
There are two ways to grow them (in Northern Europe). You can sow seeds in late summer and grow them in a cool greenhouse, when they will bloom the following spring – which is how most are grown commercially as pot plants. Or you can plant the claws in late summer and autumn. They are best grown in sunny borders, ideally well drained and protected from severe frost by a south- or west-facing wall.
They can also be grown in pots in a cool greenhouse but most kinds sold as claws are tall varieties and they will need some support when in bloom. Most common mixtures are relatively cheap and will include doubles and semi-doubles but there are more expensive F1 hybrids and single colours that are more appealing. The flowering season is short but they do make pleasant cut flowers if the taller kinds are grown. Most sold in spring as growing plants are dwarf and have a limited usefulness in pots, only blooming for about a month before they start to collapse (see top photo). If planted permanently they are best, perhaps, planted in between shrubby herbs such as lavender and rosemary, which will give some support to the flower stems, cover the dead ranunculus in summer and enjoy the same conditions. They are also useful for dry, sunny beds next to houses, though there will be no interest from them in summer.
I was lucky enough to find lots of clumps in Cyprus, several years ago. Most were white but there were some tinged with pink and pale yellow. They grew in dry, rocky spots but often in part shade and beside streams which I assume would be drier in summer. Often they grew in association with cistus.