Hi Hans, We grow Weldenia at RHS Wisley (where I work). We have several pots, all originating from one original specimen that has been divided, or root cutting taken, over the years ( a task best done in the autumn just after the leaves have died down). We use a mix of equal parts of loam, peat, perlite and grit - very good drainage is the key. We keep the plants in an unheated alpine house where they are not watered in the winter and then watered reasonably freely once the leaves appear and until they start to die down in autumn. We find they do well in quite large pots, 10 or 12 inches in diameter, which you need to accommodate the large tuberous roots once the plants reach maturity. Give them full sun and they should reward you with a good display of their beautiful, pristine - almost glowing - white flowers which have bright yellow stamens. The flowers tend to open properly only in bright sunlight, but I forgive them that because when they do they are such a stunning sight! Paul Cumbleton Berkshire, UK Zone 8