Calla are deciduous or partially evergreen herbaceous perennials growing in shallow water, with glossy dark green leaves and arum-like white spathes surrounding yellowish flower spikes, sometimes followed by dull red berries.C. palustris is a rhizomatous aquatic perennial with broadly heart-shaped, glossy leaves and white flower spathes to 25cm in length in summer
Suitable for: light (sandy), medium (loamy) and heavy (clay) soils. Suitable pH: acid and neutral soils and can grow in very acid soils.
The plant contains calcium oxylate crystals. These cause an extremely unpleasant sensation similar to needles being stuck into the mouth and tongue if they are eaten, but they are easily neutralized by thoroughly drying or cooking the plant or by steeping it in water
