These are superb plants which deserve to be much more widely grown. They are tuberous herbaceous perennials. They can twine to a height of about 3m when mature. The tubers will flower in their second/third year from seed, but take another two years or so to show their full potential. Do not think that because they can reach 3m they are large bulky plants, they have a grace and delicacy which makes them suitable for growing in containers provided with supports or through small shrubs in borders.† I grow them in full and part shade.
The botanists have had a field day with some of the twining Codonopsis species, changing their names a number of times. This new name recognises Christopher Grey-Wilsonís (the Societyís esteemed editor) contribution to work on Himalayan flora. I will not detail the earlier names as I think this just serves to confuse. The plant comes from west and central Nepal in mountain shrubberies up to 3,600m.
They are not particularly well known or grown probably because they are a nurserymanís nightmare plant. When in full growth in May and June they grow at a prodigious rate and will twine and climb everywhere, mostly failing to use the supports provided for them and mixing and tangling with anything nearby! The answer is to grow your own plants from seed and then you can enjoy them to the full. C. grey-wilsonii has clear blue flowers with a darker blue/purple inner ring. The stems of this species are dark with an almost purple hue, reminiscent of the purple in the flower. As far as I am aware this is the only species to show this characteristic.
C. grey-wilsonii 'Himal Snow' has pure white flowers on a plant with apple green stems and leaves. The flowers are campanulate, about 6cm in diameter with slightly pointed segments.
Seed seems to be always set, so there is plenty of scope for experimenting. As the very young seedlings are extremely delicate, I do not separate them until the second year of growth and then as dormant tubers. You really need a few tubers together to make a good display.
The main problem is caused by slugs and snails which may graze the emerging shoots in spring. Once growth is in full swing molluscs are less of a problem. Essentially they are trouble free and they fill a quiet time in the alpine year.