Terra cotta
Jane McGary (Sat, 02 Apr 2011 18:07:32 PDT)

I grew almost all my bulbs in terracotta pots when I had them in the
bulb frames, except for some that made extensive annual feeder roots
(such as irises), which I grew in plastic mesh baskets such as are
used for aquatic plants. Now all the pots are looking for homes,
because the bulbs have been set free in raised beds under a polycarb
roof. However, I think terracotta worked very well when plunged to
the rim in coarse sand. The bottoms of the pots were cool even when I
lifted them in midsummer.

One warning about growing large geophytes in clay pots (or plastic
ones, I suppose): they can plug the drain holes with their heavy
roots or tubers, and they will then rot. I lost a lovely Paeonia
cambessedesii and also Ostrowskya magnifica this way. Even if they
don't rot, you have to break the pot to get them out safely.

Jane McGary
Portland, Oregon, USA