Callafornia Red, Super Mac, Festival, Red Alert

Calla lilies, or Zantedeschia, are very brightly coloured and have an elegant, modern look which is perfect if you fancy a change from the ubiquitous petunias and geraniums in your summer containers. The ones pictured above are some recent introductions that were on display at a trade show in summer 2019.

With zantedeschia you usually have the option of buying large plants in flower from around late April to June (you’ll sometimes see them even earlier sold as house plants – don’t put these outside until it’s warmed up). That has advantages as you’ll be able to see the exact colour (if you buy in a garden centre rather than online) and should be able to plant them straight into your containers if the risk of frost has passed. They can be a bit pricey as plants, though, and it’s much cheaper to buy the rhizomes which are not difficult to grow if you have somewhere light but frost free to start them off.

If you buy the rhizomes you can start them into growth as early as December if you want to grow them indoors, or in late winter to spring if you want to grow them outside in the summer. The rhizomes have ‘eyes’, or raised, swollen nubs and these are on the top, so plant that side up. Plant very shallowly – the ‘eyes’ should be just visible at the surface of the compost. As always, use a good quality, free draining compost. Place them somewhere light and warm and keep them watered regularly so the compost doesn’t dry out, but don’t let the compost get soggy. Let them grow on until the risk of frost has passed, feeding with a high nitrogen feed once a fortnight at this stage. Once the frosts have finished, harden them off gradually by leaving them outside during the day and bringing them in a night for a week or two, then plant them outside. Carry on feeding them with a fortnightly liquid feed until they start flowering, then stop, as they don’t like too much fertilizer, but keep watering regularly. They should flower for a good couple of month and when flowering is over, a high potassium feed such as tomato food helps fatten up the rhizomes.

If you want to keep them for another year, treat them a bit like dahlia tubers. You might be able to leave them outside in mild areas if they’re protected (if you can move the pot to a conservatory or greenhouse for example), but for better flowering you should dig them up, let them go dormant and store them in trays of compost so they don’t dry out, in a cool, frost-free, dark place until you want to start them into growth again.

Incidentally, the coloured part isn’t actually a flower it’s a modified leaf or bract that’s called a ‘spathe’, and the flowers are small structures that are situated on the fleshy finger-shaped growth in the middle which is called a ‘spadix’.

Calla lilies are often sold as rhizomes by bulb companies, while plants can be bought in flower in garden centres.