Pest and Diseases
Virus
The genus seems reasonably free from most problems except the dreaded
ornithogalum mosaic virus. The vector for transmitting this virus is
probably sap-sucking insects such as green fly. As these pests are very
difficult to completely control it follows that once the virus is in the
neighbourhood it is only a matter of time before outbreaks will occur in a
collection kept outside. The best hope for control is to remove all suspect
material as soon as suspicion is aroused or at very least isolate the
plants at great distance or place them in insect proof cages and hope to be
able to collect seed from which to start fresh uncontaminated
populations. It is believed that the virus is not carried in the
non-fleshy seeds of Lachenalia. The virus can be recognised by a mosaic
pattern or yellowish-brown streaking produced in the leaves and distorted
stems and flowers in badly affected plants.
Bulb mites
My next most dreaded problem is the bulb mite Rhizoglyphus echinopus.
I am not quite sure if this pest attacks damaged plants or healthy bulbs.
Generally where the bulb mite is found there is also evidence of rot, the
question is which came first. The bulbs are in pots and therefore a little
more isolated than in neighbouring patches of dirt but none the less it is
difficult to see how the mite is spreads if not over land. However the
problem seems to strike at individual pots somewhat at random. My suspicion
is that the bulb mites strike first and that the damaged areas become
susceptible to rotting. Some bulbs seem to end up as a cellulose skeleton
(see illustration).
Mealy bugs
One advantage of growing the plants outside in winter is the
discouragement of mealy bugs. I cannot say that I have noticed these
creatures in any of the pots of Lachenalia although I have noticed them on
other plants in more protected spots.
Slugs and snail
It is surprising just what a nuisance these pests can be in such an
arid area. With long dry summers how do the slugs and snails do so well?
They can quite easily totally defoliate some of the smaller species and
seedlings in the collection and need controlling with suitable baits.
Fungi
Lachenalia are reportedly susceptible to fugal desease but I have
fortunately not experienced or been aware of such attacks in my collection.
General Discussion
Some species start to grow new roots soon after Christmas (southern
hemisphere) particularly if the atmosphere is a little moist and the
potting mix becomes a little damp. The first growing tips of the new shoots
usually appear about mid March with the first flowers appearing on L.
rubida from the first week in April and L. pusilla follows soon after with
L. aloides var. quadricolor not far behind in late April. An unusual
characteristic of L. rubida is that the flowers develop before the leaves
similar in some ways to forced hyacinths.
In my collection the last to flower are L. peersii, L.
purpureo-caerulea, L. contaminata, and L. unicolor that still had their
last flowers as late as the first week in December. This gives the genus a
flowering period of eight months. The largest number of species flowering
at any one time was 38 species or cultivars during September with 29 in
August and 31 in October.
The period for which a particular species population stays in flower
varies from species to species or cultivar to cultivar. Looking at
collected data L. reflexa holds the record for the species with the longest
flowering season being recorded as commencing flowering at the beginning of
June and continuing until October, a total time span some 16 or 17 weeks in
duration. Others to cover fairly extended periods are L. aloides var.
quadricolor 2 weeks, L. aloides var. vanzyliae, L. arbuthnotiae, L.
bachmannii, L. bulbifera, L. pustulata, all flowered for 10 weeks, with
others like L. rubida not far behind. Those that appear to be quickly over
are L. algoensis, L. aloides cv. Nelsonii, L. fistulosa, L. liliflora, L.
margaretae, L. peersii, L. purpureo-caerulea, L pusilla, L stayneri, L
trichophylla and others flowering for only 4 weeks. The extreme seems to be
L. orchioides var. parviflora and L. ventricosa that were in flower for
only 3 weeks.
References
CROSBY, T. S. 1986. The Genus Lachenalia. The Plantsman Vol. 8(3) 129-166
DUNCAN, G. D. 1988. The Lachenalia Handbook. National Botanic Gardens, Cape
Town.
DUNCAN, G. D. 1992. The Genus Lachenalia Its Distribution, Conservation
Status and Taxonomy. Acta Horticulturae 325, 1992
NEL, DOROTHEA D. 1983.Rapid propagation of Lachenalia Hybrids in vitro.
South African Journal of Botany 2(3)
PERRIGNON, R. J. 1992. Bulblet Production In-Vivo from Leaves of
Lachenalia(Jacq.). Acta Horticulturae 325, 1992
ROH, M. S. and LAWSON, R. H. 1995. Forcing Lachenalia as a Potted Plant.
Acta Horticulturae 397, 1995
In Don's most recent note he wrote: "We have been experiencing a severe
drought over the past few years and my Lachenalia have suffered rather. We
live in an area that does not receive much rain sometimes only 12 inches a
year over several years. This has not been to great a problem as at least
things did not get over watered and I could supplement as needed from the
reticulated water system. The big problem has come with water restrictions
where we have only two days a week when we can use a hose and then only 6
to 8 a.m. and 8 to 10 p.m. Couple this with temperatures over 100 and the
problem of keeping pot plant alive becomes serious. I am afraid to me blue
skies are very depressing."
From Mary Sue: Perhaps it is only the wet areas with high humidity during
the growing season that have trouble with fungal diseases (like mine) and
since Don lives in an area with much less rainfall he doesn't have this
problem. I too have saved seed of species that I worried might be virused,
dumped the plants and started over. You can't really know if the plants are
virused without having them analyzed however. Don also wrote about
different species. I'm going to add some of his comments on less well know
species to the wiki.