Cultivation of Bulbs

There are close to 2000 South African bulbous plant species and most of these are easy to grow. Enough variety to fill your garden and all the pots you can lay your hands on. From well-known species in the horticultural world such as arums, freesias and chinkerinchees to a host of yet-to-be-discovered gems. This section will provide some general information on how to cultivate the hardier bulb species. Not much is said about the fussy ones, as they are generally not the best ones to start with.

Selection of Species

To start with, you will have to choose the species you want to grow. A sensible strategy that could help a beginner on his/her way, is to focus on the hardier, easy to grow (but not necessarily common) species suitable for the garden. This will not only allow you to transform your garden into a showcase of exquisite beauty (at an affordable price), but also prepare you for the more difficult and delicate species. Furthermore, this general exposure could lead the way for specialization in one or more of the genera (e.g. Gladioli).
Although many of the hardier species can thrive in a climate vastly different to that of their natural habitat, it could certainly influence your selection. In a winter-rainfall area you may opt for winter growing or in a summer rainfall area for summer growing species. On the other hand, additional watering in the dry season may enable you to grow evergreen species in both the above-mentioned areas. Most summer rainfall species are also quite tolerant of winter rainfall.

The availability of stock could determine what you grow, although if you propagate from seed you should not find this too limiting. There are a number of commercial organizations that sell seed of a wide variety of South African bulbs and also not-for-profit organizations such as IBSA and the Botanical Society that distribute seed among their members. Visit the link section of this website for more information.


Nursery Setup

You will have to find an area outside your home that you can dedicate to the cultivation of your bulbs. This can range from anything from a couple of pots on the balcony of your flat, an under-cover greenhouse to raised beds or an open bed cultivation area. In general most winter-growing bulbous plants prefer a sunny position, while summer-growing species will do best in a semi-shaded position. Evergreen species' requirements may vary from full sun to full shade. Free air circulation is also important for most of the bulbs.
Some of the winter-growing species from arid areas are very sensitive to dew and over-watering and may only be grown successfully under cover.

Growing medium

The most important component of the growing medium is sand, preferably a medium-grained, washed river sand, although coarse industrial sand may also do. The one thing to remember here is that the proportion loam and compost in the medium should become smaller for the more difficult-to-grow species. For example, while 'easier' species such as Gladiolus carneus should be grown in a medium consisting of two parts sand, one part loam and one part fine compost, difficult species such as Gadiolus debilis may be grown in three parts sand and one part compost (or even pure sand). Despite all of this being said, there is always scope for you as a grower to discover your own ideal growing medium.

The shape and size of the plant pot should be chosen to suit the plant and also your nursery setup. This could vary from 15cm pots for low-growing species (e.g. Galaxia, Oxalis and Polyxena) to 35cm pots for species with large bulbs (e.g. Boophone haemanthoides and Veltheimia capensis).

If space and uniformity is of a high premium in your nursery it is advised that square shaped pots be used.

Planting of bulbs

The depth of planting is the next most important thing to consider when planting your bulbs. At the worst this could lead to the demise of your bulb, or at least it could prevent it from flowering. For instance, at least two thirds of the neck of bulbs of Boophone disticha should be exposed or otherwise they may be at risk of rotting. If Babiana bulbs are not planted deep enough, they will pull themselves down to the optimum level before they start to flower.

Propagation

Buying mature bulbs is the easiest and quickest way to get a pot or even a bed full of flowering bulbs, yet it could become quite an expensive exercise and the availability of bulbs is often a problem. An innovative solution is to propagate your own plants at home.


Seed Propagation

Sowing seed is one of the best ways to increase the numbers of your plants. Winter-growing species should generally be sown in autumn (March to May) and summer-growing species in spring (August to October). Evergreen species from the winter-rainfall region would do best when planted in autumn and those from summer-rainfall areas are best sown in spring. As always there are exceptions to the rule (the members of Amaryllidaceae family), which should be sown as soon as they are ripe. Most of the species will germinate quite readily.
Sow the seed sparsely (to prevent overcrowding and to allow sufficient room for the development of root systems) in deep seed trays or pots. Cover the seed of most species with a thin layer of sand, but the large fleshy seeds of the amaryllid family should just be pressed into the soil to rest at or just below the soil level. The seedlings should be left undisturbed for at least the first growing season and in many cases transplanting should only take place after two or three seasons. Most of the species will flower in their third season.

Vegetative Propagation

  This refers to the wonderful ability of some bulb species to create identical plants vegetatively. One category of vegetative propagation uses offsets, bulbils and cormels. These "new bulbs" should be removed from the parent bulb during the dormant period when they are large enough to be handled. Offsets from bulbs with perennial roots (eg from members of the Amaryllidaceae family) should be planted immediately, while the rest may be stored until the next planting season - either spring or autumn. The production of bulbils and cormels is reflected in the names of some species,for example Lachenalia bulbifera and Watsonia meriana var bulbillifera.

A second method is the division of rhizomatous rootstocks, where plants of species such as Agapanthus, Clivia and Kniphofia are lifted in a large clump and then divided. The leaves should then be cut back by about a third and the bulbs planted immediately.

Thirdly, members of the genus Lachenalia may be propagated using leaf cuttings. The leaves should be virus free and still in active growth. Plant them in a well-drained medium with the base of the leaf about 1 cm below the surface. After a couple of months, bulblets should form at the base of the leaf. These may then be planted the next year to produce flowers in the second growing season.

Watering

Winter-growing species should be watered thoroughly when planted and then only once leaf shoots start to appear. Thereafter the plants should be watered well at regular intervals (e.g. once a week) than light or irregularly. A number of species from our arid areas do not respond favourably to crown watering as it may cause rotting. This is especially a problem under glass and in still and damp weather. Watering from below could be a solution here. Be careful not to over-water container plants (it is preferable to have a growing medium that is too dry than too wet). A well-drained soil medium in a pot that is preferably tending towards the small side, will help to limit the likelihood of over-watering. The exceptions are species that grow in permanently damp places, for eg. some Geissorhizas (e.g. G. darlingensis and radians) and Onixotis, which require continually moist medium during the growing season. Watering should be withheld when the leaves start to turn yellow.
In contrast to the winter-growing species, summer and evergreen species are generally less specific about their watering needs. Water most species about once a week (if there is no rain). Some of the summer-growing species from drier areas may even be watered less frequently.

Feeding

The main goal of feeding is to replace the nutrients in the soil as they become depleted. With frequent repotting (every year or alternate year) it is therefore possible to grow most of the South African bulbs without feeding. Larger bulbs (e.g. Amaryllids) should be left undisturbed for longer periods of time and will therefore need feeding when cultivated in pots. However this does not mean that bulbs will not respond well to feeding. Use a liquid fertilizer low in phosphate and nitrogen and high in potassium at monthly intervals in the growing season.


Pests and Diseases

This section discusses some of the pests that could attack your bulbs in cultivation. Details about other diseases and the treatment options available may be found in the literature.
Like most bulbs in cultivation, South African bulbs are susceptible to infestation by mealybug. These insects could spread viruses and immediate treatment is therefore necessary. Other plants susceptible to viral infections are Brunsvigias, Lachenalias and Ornithogalums. Infections are usually detectable in deformations or unusual colouration in the flowers or leaves. Agents such as mealybug, aphids, snails and cutting instruments transmit these viruses from infected to healthy plants. It is therefore advisable to isolate (and possibly destroy) plants with these symptoms.

 

Home

 
Copyright 2010. Powered by Skytouch Media