In growing season, fertilize it every month with a liquid fertilizer for bulbs. Suggested uses. Boggy damp conditions, Pond/In water. Soil type. Cultivation. Arum lily is a demanding plant and needs regular fertilization. Caution - Harmful if eaten/skin and eye irritant. Also known as Water Arum. Plant in loam (lime-free) soil (ideally in planting baskets) in water up to 25cm deep, in full sun. Follow manufacturer’s instructions to avoid over fertilization. Plant Type - Pond Marginal Arum lily care and maintenance is relatively simple: Fertilizer. Calla prefers acid and neutral soils and can grow in very acid soil. Find help & information on Calla palustris bog arum from the RHS Bog Arum (Calla palustris) This free growing marginal plant produces white flowers, which turn into bright red seed heads. Clay, Loamy, Sandy. Calla palustris (Water arum) will reach a height of 0.5m and a spread of 0.5m after 5-10 years. Soil pH The heart-shaped leaves are 6-12cm long on 10-20cm petioles. Bog arum (Calla palustris) is a good marginal plant for softening edges of ponds. Arum Lily Care. The flowers comprise of a yellow-green spadix in a white spathe 4-6cm long. This native plant has minute greenish flowers on its main spike but is enclosed by a spectacular white spathe from May to August, with clusters of red berries (toxic to young children) from August to November. Soil drainage. Aquatic, Architectural, Bog garden, Waterside. Calla Palustris is one of the few plants known to be pollinated by snails, they are attracted by the plants scent. Calla palustris is a creeping native UK plant that is excellent for hiding the edges of an artificial pond. Mulching