ZESTFUL ZANTEDESCHIA

THE A – Z OF BEST PRACTICE!

Known as the arum lily (the outdoor white types in big swathes) or calla lily (the tender, colourful types) around the world. These remarkable plants comprise eight species that grow in the wild, generally in areas with seasonal rainfall such as the grasslands, fynbos and savannahs throughout the country, with many of the species growing between rocks to protect their tubers from foraging animals.

Firstly, a question we often hear is: “should or can these be planted in water?” When dealing with the species Z. aethiopica, the answer would be sure, as you’ll find it on the margins of streams and rivers, in vleis or on the edge of ponds, if not in the pond itself. While the other plants in the genus are happy to have their feet ‘wet’, this mainly refers to making sure they aren’t in a dry spot.

The new generation of coloured hybrids which are now available in a range of jewel-like hues are perfect for the garden or the pot. The various species’ foliage heights range from 60cm – 1m, with the flowers making them even taller.

Depending on the species, the underground storage ‘root’, which is actually part of the stem, is variously referred to as either a tuber or a rhizome, the latter specifically for the Zantedeschia aethiopica. New varieties produce more blooms from a given tuber size, with the number of flowers directly proportional to the size of the tuber. It will keep increasing in size from year to year when looked after properly.

WHERE TO GROW THEM

Zantedeschia grows best in temperate climates but will grow happily as long as they get watered often enough. With the exception of the common white arum which will grow in full sun or semi-shade (sometimes in the deep shade too, although they won’t flower as well), your Zantedeschia will need at least 6 hours of sun a day.

They need rich soil with lots of well-decomposed plant matter, so get the best compost you can to enhance your soil.

HOW TO PLANT ZANTEDESCHIA

Outdoor

How do you tell which way is up? Occasionally, it’s not entirely clear which way you should plant your ‘bulb’. Well, one side of the tuber or rhizome will be smoother than the other. This smooth side is the base, so that goes down.

Plant them out in spring or early summer, with the tubers at least 15 – 30cm apart from each other. Dig the soil over and make sure it’s well-draining but not sandy as too much water will leach away, then plant about 5cm under the soil surface. Don’t water them too heavily at planting. Once their rhizomes are established, water once a week or more often if the weather is very hot or dry. Z. aethiopica can be planted in your garden bed or planted into a pot and submerged into a pond.

Zantedeschia really enjoys having regular feeds of organic fertiliser and applications of compost, so don’t skimp on it. Give them food and they’ll give you bigger and better flowers. A slow-release 3:1:5 fertiliser once during spring and again in summer is the way to start. Then give them a high nitrogen fertiliser fortnightly when they’re actively growing, but not when they’re flowering. At this stage, the plant will grow quickly, so up the watering.  Once they’ve flowered, give them some food high in potassium once a week.

Indoor

They’re fabulous when planted in a container so go for the largest planter you can, preferably terracotta as the porous nature allows air and water to pass through the walls of the pot which will help guard against diseases caused by overwatering, or root rot. The only downside is that the soil will dry out quicker, so you’ll need to water more.

Don’t keep the pots in a dark corner – they need sunlight. When their foliage starts dying down towards winter, you can just move the pot to somewhere that their natural process of going dormant can continue normally.

How do you know when dormancy is? Well, once it’s finished flowering, reduce watering. The leaves will eventually turn yellow and then wither, which is when you stop watering for two months. Keep an eye on how many months have passed, and then start up again slowly!

An indication that your beauties are ready for a bigger pot is when the roots start to look crowded. Root-bound plants won’t thrive, so replant them if you notice an issue with their roots. Get a pot that is at least 5 – 7.5 cm deeper and wider than the old pot. When repotting, carefully lift the plants out of the smaller pot and gently place them into the larger one, watching out for their delicate roots. Then fill the new pot up with soil to around 2 – 3cm from the rim of the pot. Keep the soil moist consistently for a few days after repotting, ensuring it isn’t soggy or waterlogged.

Keep in mind that all parts of the plant are poisonous, so you’ll want to keep them away from your pets and children.

HOW TO CARE FOR THEM

Once you have planted your bulbs, just leave them to their own devices, as they’ll keep coming back year after year. Most important is to ensure that you give them some compost mulch in spring, and regular deep watering through the warmer seasons once the flowers have appeared until the end of the blooming season. Once they move into their dormant phase, hold off the watering as many varieties need a two month dry spell.

If however they have been watered, they may keep going and their foliage could be damaged by black frosts, especially in the colder regions of the country. Just cut this away once all danger of frost has passed.

As they’re dormant during cold winter months, this means they’re fairly hardy. Do keep in mind that the colourful hybrids are less hardy, so if you have a very cold garden, protect them with hessian or straw.

Tubers of the hybrids will remain true to their colour, but we’d suggest that you remove all dead flowers so that they don’t set seed, as any that germinate generally results in indistinct colours coming through. 

Do take some time out to remove dead and decaying debris from around the plants as this serves as a food source for fungal pathogens and as a hiding place for pests.

When cutting flowers for the vase, don’t use a knife to cut them off the plant as water could get into the remaining stem and could lead to tuber rot. Get down to the base of the flower’s stem and pull it out. Do wear gloves to protect your hands from the sap.

PROBLEMS? NO PROBLEM!

If you don’t get any flowers coming up, the problem is probably too much nitrogen or is with the soil. Although they are happy in any rich, well-draining soil, they are most content in soil that has a pH of between 6.0 – 6.5. So if you’re soil is high on either side, you’ll need to amend the pH.

If the soil is within those limits, it may be a case of overwatering. The soil needs to be moist, not sodden. This could also lead to fungal infections of the plant.

Too much nitrogen in the fertiliser may also lead to browning on the edges of the leaves, as well as drooping stems and flowers.

If it isn’t getting enough light indoors or sunlight outdoors, you’ll need to move the plant – bearing in mind that any changes will still mean about four weeks before flowers may be produced.

Happy gardening and may you enjoy a profusion of happy Zants!