Some people seem to think that there is a lot of mystery in growing these stunning summer flowering plants - but its really quite simple, once you understand just what makes them tick. I`ve included all sorts of information about these interesting South African plants to help you grow and enjoy them as much as I have.
What is a Calla?
A calla is a starchy underground organ (like a potato or tuber) which stores food for the plant during its dormancy or rest period. Hidden inside these tubers are all the new leaf and flower shoots which are made during the previous growing season. After a winter sleep they come out to delight in the spring.
Tubers are not to be confused with a bulb which consists of swollen leaf bases encircling an inner one, like an onion, or overlapping scales as found in liliums. The flowering stem of a bulb grows up through the middle of the bulb.
Calla tubers are normally purchased in summer months with flowers open, and generally look very striking. They can sometimes be purchased during dormancy in the winter months although this isn`t so common.
Do not confuse these summer flowering callas with the winter flowered variety often being used for funerals, and sometimes wedding bouquets. It is more commonly known as an Arum lily, sports white - greenish flowers and is generally found in wet or boggy places, often growing wild.
What do I do with my Callas When they finish flowering?
Callas, when purchased during summer, are normally in a pot. When flowering has finished move the whole plant in its pot to a part of your deck or garden that still gets some rain, but doesn`t get overly wet. When the leaves start to turn brown and fall over, move the plant to a place where it gets less moisture. I store mine in my garage.
When the leaves have died down completely, I remove the tubers from the potting mix, replace the mix and replant ready for the next season. The reason that I repot early is that if I don`t do it now, I invariably forget until the shoots come up in the spring - and then my chance is past. But if you would rather plant them in the garden then, instead of repotting them, store them until late winter - early spring and plant out before the shoots sprout.
Good storage of the tubers is very important. If you keep them in a damp or wet place, the tubers can either rot or get a number of possible diseases, none of which will do the plant any good. But on the other hand, if the bulb gets too dry, it can calcify and die from the inside out, which is why I leave them stored in a mix of some sort - some moisture but not too much.
Temperature during storage is also important. Callas do like to have a winter rest of 12 weeks or so. They like to hibernate in a colder temperature than that of a normal growing season - but note, they don`t like to be frozen. Ideally about 10deg C will keep them happy, cold and resting.
How and where do I plant the Tuber
The general rule is to plant the tuber 2-3 times its diameter deep. That is, a 5cm tuber goes about 15cm down. Callas don`t like wet feet, so plant in a well drained area, particularly if you don`t want to lift them each year.
How can I propagate my Callas?
If you lift the tuber from a pot in spring you will notice a larger one - sometimes called the mother tuber, and some smaller ones - generally attached to the mother - which are called offsets. If the offset is just about naturally separated from the mother, then carefully cut or break the two apart. You will have a whole new plant.
How Many Flowers Will I Get?
The number of flowers is largely determined by the size of the tuber. The bigger the tuber, the more flowers you will have. Generally, a tuber of less than 3cm diameter might not flower. Also, the larger the tuber, the larger the flower size - to a point. Very few calla tubers exceed 10cm, so this becomes a limiting factor on the flower size. Remember, plants are generally sensible, and won`t do something above ground that they cannot support from below.
Why Did My Callas Have More Flowers When I bought It, than It Does This Summer?
The reason for this could be that some growers dip their tubers in a hormone to encourage all the shoots on the tuber to flower. No it is not genetic engineering, but simply a chemical encouragement to flower, if you like. But relax, let your tuber grow larger, propagate it if you want more, and enjoy - it is now behaving more naturally.
Are Callas Difficult To Grow?
Providing you meet their needs in terms of fertiliser and water, callas are generally easy to grow, and always repay any effort that you put into them.
As is true of most plants, callas are susceptible to some diseases. The worst of these is a bacterial disease called Erwinia - which you may have smelt in your potatoes. You will only smell it when you are handling the tubers themselves. It emits a terrible stench similar to rotting flesh - not something that you will too easily forget. If your plant is struck down with this disease during its growing period you will see its leaves or flowers suddenly tip over from the base of the stem and go mushy.
There is no known cure, and all I can suggest is that you remove diseased foliage and destroy it (don`t go near your compost bin with it!) Drench the remaining plant with Oxychloride or Champ DP on a weekly basis for 3 weeks or so. Following this, ensure that your plant isn`t overly wet, and leave it well alone till the natural dormancy sets in around autumn. Then treat exactly as a normal healthy plant.
Don`t be put off by the slim possibility of this disease. The chances of this happening are rare - but at least you are now informed and, armed with information, can cope should the unlikely occur.
You will most likely find that callas are not generally affected by many insects; although insect control may be required should aphids be seen.
Is Regular Spraying Of Callas Recommended?
To be honest, it`s not really necessary. To my mind, they need to build some natural resistance of their own, and so long as you keep them healthy (just like a person - regular food & water) they should serve you well. If however, if you do see insects on them use Yates Super Shield according to the packet instructions.