Potting up cinereum and subcaulescens geraniums
Cinereums, along with the subcaulescens species of geraniums should really be treated as alpine plants.
In the longer term they should be planted up into clay pots, sand beds or rock gardens where they will be in a free draining location protected from winter wet.
If you follow these steps to potting up your cinereums etc you should have success with them year after year.
Line the bottom of your clay pot with a piece of fine mesh. This will keep the compost in and the earth worms out. Do not use crocks at the bottom of your pot, these will not improve drainage.
Pot up your plant with a compost for alpine plants; a low-level nutrient compost with added grit to improve drainage.
Finally apply a top dress of grit mulch to protect the crown from winter wet and protect the delicate flowers from soil splash.
It is recommended that alpine plants are protected from winter wet, and where possible should be brought into an unheated greenhouse or cold frame (or similar) to over winter.