Propagation
The methods available for the propagation of Lachenalia is probably
as varied as almost any other bulbous plant. These include seed, bulbils,
offsets, division, leaf cuttings, scaling, micro propagation and tissue
culture.
Sexual propagation
Seed
The principle means by which Lachenalia are propagated would have to
be from seed. It is, after all, the chief mechanism by which plants spread
and practically the only way they can adapt to changing environmental
conditions. For collectors, growers, hybridists etc this usually small
change but occasionally large change in morphology can be cause for joy or
disappointment depending upon whether you are looking for new hybrids or
trying to maintain species integrity. In order to maintain unaltered
species or hybrid characteristics one needs to use a vegetative means of
reproduction such as separating offsets, bulbils, division, scaling,
micro-propagation and taking cuttings.
Growing from seed has the advantage that it maintains the small
variations that exist within a species and which are responsible for hybrid
vigour. These variations are found quite naturally in plants within a
community that have propagated by sexual means, that is by seed. A number
of growers have noticed that their specimens of Lachenalia lose vigour over
time and this is thought to be due to virus which may invade the plant but
not cause dramatic visual effects. To maintain integrity of species when
propagating from seed one might try housing groups of the same species in
cages made of a fly proof netting as this will almost guarantee no crossing
outside the cage. However there will be few if any pollinators in the cage
and hand pollination will have to be carried out.
Seed of Lachenalia seems moderately easy to grow, the germination
process has no hidden requirements such as stratification and if planted in
autumn (fall) in cool conditions germination will follow. The main aim
should be to provide as long a growing season as possible. The seedling
bulbs have a much greater chance of surviving the first dormant period if
they are as large and plump as possible without being too 'soft' i.e. not
forced with too much nitrogenous fertilizer. In the southern hemisphere I
have successfully grown bulbs from seed planted at times from February
through to July. During this time I keep them frost free and perhaps just
as important when spring arrives keeping them cool and out of hot middle of
the day sun.
In my first few years growing this genus from seed I made my own
growing media from course sand, peat and a little loam as a pH buffer.
Later I tried some proprietary seed raising mix and found the results
seemed no better or worse only easier and I have continued to use this mix.
The main criterion seems to be to try to keep the compost moist but not
wet. After watering I leave the containers to become almost dry before
giving further water.
I sow small quantities of seed in half pots with seed separated by
about 1 to 2 cm (1/ 2 to 1 inch) and just covered with compost or sand. The
ideal time to sow seed here is March to May. If I sow seed later I find it
advisable to try to extend the growing season by being very vigilant in
keeping the environment cool and with enough moisture as we progress into
spring. Allowing the seedlings to become excessively hot or dry will induce
premature dormancy or death. Very small bulbs are difficult to store dry
through summer to autumn. When the plants become dormant and the leaves
have died back I try to find out how large the bulbs have become. Bulbs
over about 4mm (0.2ins.)are lifted and stored being replanted next autumn.
If the bulbs are small to very small, say around 2mm (0.1ins.), I tend to
leave them in the same pot for a further season. The small plants will need
feeding and I use a liquid that is relatively low in nitrogen, as I do not
wish to encourage high growth rate at the expense of good bulb structure.
Seed seems to store fairly well and will stay viable for at least
five years at room temperature (Duncan 1988). I have also heard of seed
being viable after eight years.
Asexual propagation
This includes all vegetative methods of propagation. All these
methods except perhaps the use of tissue culture have the disadvantage that
any virus contained in the parent is almost certain to be passed to the
protogyny.
Bulbils, Offsets and Division
Through the 110 species of Lachenalia there is wide variation in
inclination to produce offsets. Some like the L. aloides group produce a
profusion of bulbils that look similar to grains of rice other species have
a tendency to produce offsets or side bulbs that can vary greatly in size
and yet others divide into two or more relatively similar sized bulbs. Some
seem to not reproduce by these means at all but compensate by being
prolific seed producers.
Bulbils may be produced in relative profusion around the parent bulb
or may result from damage to the leaf bases or bulb scales. A number of
species may occasionally produce bulbils on the top of an inflorescense
(very top of the rachis) or on the edge of a leaf. L. bulbifera, as its
name suggests, can produce bulbils at or above ground and others like L.
namaquensis and L. moniliformis produce long stolons or underground stems
to push the bulbils away from the parent.
The small bulbils are treated similar to seed and will produce year
old bulbs that will be similar in size to one-year-old seedlings that have
had a full season to develop.
Depending upon size offsets may flower in the first year of
separation from the parent bulb or may require a further year of growing on
to achieve a first flowering.
Division seems to occur when the bulbs reach a certain size and may
result in the bulb dividing into two or more bulbs of roughly equal size.
Frequently the resulting bulbs are sufficiently large to flower in the
first season after separation.
Leaf Cuttings
An interesting method of propagation is the use of leaf cuttings in
rather a similar fashion to those taken in the genus Veltheimia. The
simplest method is to take a mature leaf at about the climax of its growth
and well before it becomes senescent. For proteranthous species, i.e.
flower after the leaves have matured, the leaf cutting is taken just before
flowering commences. The leaf is cut off near the base and placed upright
in sharp sand with the base at a depth of between 2 and 5 cm (1 to 2 ins.).
Variations on the striking medium can include vermiculite and or peat moss
mixed with sharp sand at a ratio of about 1part vermiculite or peat to
3parts sand. The containers are then placed in a cool spot out of direct
sunlight. The number of bulbils formed and their size will depend upon the
length of cut surface and the size of leaf material used. This method most
suits the broad-leafed species and cultivars with the grass like leaved
species being less successful. To obtain a greater number of small bulbs
the leaf may be cut into a number of cross-sections although the sections
farthest from the base of the leaf seem to be more reluctant to produce
bulbils. Personally I do not subdivide the leaf in the hope that the
bulbils produced will be larger and reach flowering size sooner. With a
leaf cutting taken at the optimum time some of the resulting bulbs may be
large enough to flower in the next season. Thus by using this technique
flowering size bulbs may be produced one year ahead of seed produced plants.
I have also noticed bulbils being formed at points where leaves have
been damaged usually below soil level. This may be a technique worth trying
with species that do not readily produce bulbils or do not divide readily.
The stress produced on the parent bulb is far less and one has little to
loose but something to gain.
Chipping
Propagation by such techniques as chipping has been carried out
successfully on some horticulturally significant species that are shy of
division or bulbil production. Although I have not tried this technique I
have noticed bulbils being produced upon damaged bulbs. Pest damage
sometimes removes substantial amounts of the bulb either from the outside
or sometimes in the bulbs centre. In these cases I have noticed small bulbs
being produced at the damaged surfaces sometimes while still in the pots
during the dormant period or while in storage.
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Micro-propagation
In this method of propagation very small portions of the growing tip
of plants are cultured under sterile conditions in a test tube. This is
known as tissue culture and for the genus Lachenalia in which leaves can be
induced to produce the required growth tip it is possible for the whole
procedure to be carried out by using a small section of leaf. Nel 1983 (see
references) described a process whereby 2000 plants were produced in 8
months from a single leaf using 1cm2 pieces.
This procedure is clearly out side the scope of many amateur
propagators but for the sake of completeness I thought it worth mentioning.
Having said this I have read of amateurs setting up a system in the home
that has been partially successful although I cannot find the reference.