But plant collections need places to grow. Parker was always interested in having a rock garden, but living in the city curtailed that idea. So he started adapting containers for growing alpines and learned to make troughs of hypertufa (a lightweight composite of cement, peat and perlite that mimics natural tufa, a porous limestone). In addition, he was always on the lookout for unusual pots.
The silvery rosettes of cobweb sempervivum.