National Council for The Conservation of Plants and Gardens
National Collection of the Genus Codonopsis and Allied Genera
In their natural habitat Codonopsis grow on cliffs, stony hillsides and the edge of light woodland in well drained soil with plenty of moisture in the monsoon season. In the absence of a rainy season in Lincolnshire we find they survive well without extra watering provided that the soil is not too dry and dusty.In the garden winter wet is their main downfall. We know from bitter experience that they do not like unimproved heavy clay soil but are happy in a raised bed or a slope. Most species like to have their feet in shade and their tops in sun or light shade so a host shrub is ideal, supporting the rather lax growth and helping to dry the soil in winter. We are experimenting with some of the smaller ones in our leafy woodland soil and also in the lee of rocks on a stony scree.
They are readily raised from seed sown thinly in a gritty/sandy mix in February with germination occurring a few weeks later. Our mix is 2 parts JI Seed compost, 1 part gritty sand and 1 part fine grit, filling square pots ¾ full topped up with sand. The seeds are spread thinly on top and a final layer of grit to finish. These are placed in an open sided, shaded greenhouse.
We keep moving the whole potful into a larger pot for the first summer every time the fine roots reach the bottom In the autumn we knock them out of their pots and pot up large tubers singly and smaller ones together to grow on for a further season. Our mix for this and all stock plants is 2 parts Melcourt multi purpose compost, 2 parts Melcourt propagating bark and 1 part each of fine grit and sharp sand.
Our stock, which is all re-potted in the autumn is placed in a dry frost free environment for the winter. At this stage we often find that offset tubers have been produced which are grown on.
Young plants generally flower in their third or fourth year. They are much loved by slugs so we do have to be vigilant. Also be aware that mice might visit during the winter months.
Our aim is to grow as many different varieties in the garden or in very large pots and the only maintenance then is to move the latter under cover for winter.
Apart from seed and offset tubers we are experimenting with cuttings as a means of propagation.