Maintaining and caring for your bulb collection

We suggest following these four important steps to maintain a successful and happy bulb collection.

Select the correct pot size for each species
Make sure each species has the ideal growing medium
Ensure each species receives the right amount of sunlight
Each species requires the correct watering schedule

Pot size: It is important to select the correct size and shape of pot for each species. The smaller species can be planted in smaller shallower pots where the larger bulbs require a much larger and deeper container to do well. Some species enjoy being planted deep in the soil where others need to be planted with half the bulb exposed.

Growing medium: One of the most important requirements for bulbs is a very well-drained growing medium. Generally, winter growing species prefer a sandy, nutrient poor medium and do not require regular feeding. The soils in their natural habitat are usually very poor. A mixture of river sand, course river sand and silica sand generally works well for winter growing species. It’s important that water drains easily through the medium. A general rule is the dryer the habitat that the bulbs come from, the more well drained the medium. On occasions when you feed winter bulbs, we find it best to use water soluble fertilizer with a high potash content. Summer growing species generally require more regular feeding and humus-rich growing medium. A mixture of river sand, silica sand, composted pine bark and well-decomposed organic compost/leaf mound compost is a good combination. It is important for the medium to be well-drained too.

Sunlight requirement: It is important know where the bulbs grow naturally to understand each one’s sunlight requirement. Many winter growing species occur in hot dry areas exposed to full sun, although this is not always the case. Some only grow in areas sheltered by rock faces and boulders or in places protected by vegetation. Many summer growing species grow in areas that receive dappled light so generally a semi-shade environment is best for them. It is important to give each species a place that receives the correct amount of sunlight, otherwise it could affect both the health of the plant and its flowering.

Watering: It is always safer to water less regularly instead of too often, many problems with bulb health are a result of too much water. There are bulbs that enjoy a lot of water, a few enjoy being submerged in water, but most are waterwise and should not be watered too regularly. Although many summer rainfall species can tolerate water in winter, most winter growing bulbs should not get any water in summer, or they rot and die. Most winter growing bulbs should get a good watering every 7 to 10 days during the winter growing season and a completely dry summer. If you are growing winter bulbs in a summer rainfall region it’s important to keep them under roof cover, particularly during summer dormancy.

The below extract on bulb cultivation is taken from Graham Duncan’s book ‘Grow Bulbs’ which was published by SANBI, a great book for anyone wishing to start a bulb collection. The best place to order it from is the Botanical Society Bookshop at Kirstenbosch: WhatsApp number +27 65 922 6163, or landline 021 797 2090 or www.kirstenboschbookshop.co.za

Indigenous southern African bulbs are often perceived to be difficult to grow. While this is true for some species, many can be grown and enjoyed with adherence to just a few basic principles. Some of the plants recommended here are sufficiently robust to perform well under the vagaries of general garden cultivation. However, while it is easy to imagine that the smaller bulbs such as geissorhizas, hesperanthas and romuleas, for example, might flourish in rock garden pockets from year to year in temperate climates, experienced growers know that rarely is this the case; the corms may perform well the first year, and with luck, the second, but thereafter an ever-dwindling number of corms survive, due primarily to their inability to withstand indiscriminate garden irrigation during the dormant period, and poorly drained soils. In addition, the delicate nature of many of these species precludes their cultivation in gardens in their inability to perform well under extraordinary weather conditions such as strong wind and heavy rainfall, or stand up to the devastating effects of problem animals such as porcupines, molerats and guineafowl, attack by Insects and soil-borne diseases. Cultivation in pots in a protected environment is the only way in which to cultivate these species successfully, and grown this way, the exquisite yet often ephemeral nature of their flowers, many of which are heavily fragrant, combined with their often interesting leaves and fruits, can be appreciated at close quarters.

It is important to note that numerous southern African bulbs have invasive tendencies when introduced into climates with similar growing conditions to their wild populations, but where endemic animal and insect pests and fungal pathogens that naturally keep populations in check, are absent. Examples of these include Agapanthus praecox, Gladiolus caryophyllaceus, Lachenalia reflexa and Watsonia meriana that have escaped into the wild in south-western and southern Australia, and Oxalis pes-caprae that has become naturalized in many parts of Mediterranean Europe, and especially in southern California where it now rages out of control.

Whereas cultivation techniques for most South African geophytes are known, those of several species remain unsolved and challenging. As early as 1837, the amaryllid expert William Herbert reported the deciduous winter-growing amaryllid Cyrtanthus carneus to be impossible to grow, the mature bulbs gradually diminishing in size, and finally rotting, a situation that persists today. Similarly, the deep-seated bulbs of the pyrophytic amaryllid Hessea cinnamomea rapidly decline and perish in cultivation, despite provision of a perfectly well-drained, acid, sandy growing medium.

A large number of southern African geophytes have highly restricted ranges and many of the species included here fall under various IUCN Red List categories of threat in the wild, ranging from Rare (such as Strumaria barbarae) to Vulnerable (such as Cyrtanthus eucallus) and from Endangered (such as Moraea elegans) to Critically Endangered (such as Gladiolus aureus); cultivating these species successfully makes a real contribution towards preserving them for the future and preventing their extinction. Knowledge of the habitats and weather conditions in which a bulb species occurs naturally is of great importance in learning how to cultivate it successfully. The most significant of these is the particular growth cycle the species follows (winter-growing, summer-growing or evergreen) that provides the all-important cue as to when the dormant period should be imposed in cultivation, especially amongst the deciduous species. Following this, knowledge of soil type, moisture requirements, light levels and degree of cold tolerance provide the grower with the necessary information to simulate optimum conditions.

The calendar months used in this book pertain to those in the southern hemisphere; to obtain the corresponding month in the northern hemisphere, six months should be added or subtracted. In the northern hemisphere, spring is usually the period March to April, and autumn is September to October.

Maintaining a bulb collection

A mistake often made by growers of species collections is that, carried away with enthusiasm, they allow their collection to become too large, resulting in insufficient time to attend to each member. It is imperative to decide at an early stage how much time one has available to care for the plants and, difficult as it may be, to give your collection a theme and specialize in particular groups or genera, to which one can devote sufficient time. Winter-growing, summer-growing and evergreen species should be grouped separately to facilitate easy watering. Of utmost importance is the elimination of weeds, pests and diseases as soon as they appear. Weeds that have become well established should not be pulled out (thus disturbing the contents of the container) but rather cut off at the base, just below soil level. Timeous pest and disease control is essential in maintaining plant health and preventing their spread to other members of a collection.

Apart from the health of your plants and the contribution one can make to conservation by cultivating threatened bulbs, the scientific importance of a species collection is greatly enhanced by preserving as much information about the origin of its members as possible. The single most important aspect of this is the information provided on the label with each species, with its name, wild locality at which it was collected or other source of the material, date and a reference code to more detailed information stored elsewhere. Labels should be securely inserted into the soil and ideally, the reference code written onto the container itself.

Keep your collection pure by isolating. hand pollinating and preventing colonization by species from
adjacent pots by timeously collecting seeds before they fall, and discarding developing seed capsules of
dubious parentage. Any hybrids that may appear must be rooted out immediately.

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