Lachenalia from Don Journet--Part 3

Mary Sue Ittner
Tue, 06 Feb 2007 10:23:33 PST
Pest and Diseases
      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.

      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.


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
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.

More information about the pbs mailing list