If a cactus plant
is grown in plenty of light and warmth, in a suitable compost, and with
proper attention to watering - the reward should be good flowering. We
cannot imitate the intensity of light they enjoy in their native habitats
- mainly because we are so far north, but longer summer days do compensate.
Warmth is generally easier to maintain. Rebutia will tolerate down
to about -5C but some others need to be kept at not less than 10C. How can
these conditions be achieved in practice.
Our weather conditions make growing cacti and succulents outdoors, all year round, a very
doubtful proposition. There is a report that a lady did this in Alexandria (Dunbartonshire),
but this has not been proved. Most growers do put plants out during the summer which
probably does them a lot of good. Some growers make use of garden frames which allow cover
if the weather deteriorates, or even if there is prolonged sunshine and little wind.
In most cases plants are grown in a greenhouse or conservatory. Small collections have been
grown on a window-sill, and won prizes.
The first environmental condition of greenhouse
culture is proper lighting and the second is almost certainly good ventilation. It is said
the latter is best met by the type of greenhouse used for alpines. These usually open
all along the sides, and even the roof. In the author's view the superstructure of such
greenhouses is substantial and cuts the light down, quite a lot. Whether there is an
advantage in having special glazing in a normal greenhouse is a moot point.
Branch committee members were asked about heating at the same time as being asked about
In all cases heating was provided by thermostatically-controlled electric heating, at
a setting of about 48-50F. On one occasion this was boosted by gas heating. Particularly sensitive, or valuable plants were taken indoors
for the winter. A centrally-heated conservatory avoids such problems of course. None favoured
oil-heating. Whether this was because of the problem of water-vapour, or perhaps the danger of
mal-function when plants have been known to be blackened by soot by morning.
One member who grows mountain cacti in a cold greenhouse, and succulents indoors, provided
no heating, except for a large candle (in an 8X6 greenhouse) when temperature fell below -5C
he would put two layers of newspapers over the plants by about 16.00 hours. Some Rebutia, it
is said, are under snow in the Andes, for six months of the year and the newspapers are intended
to simulate snow cover. When temperature fell below about -12C a large 75mm candle was used,
and that seems to work.
'Damping down' was standard practice for other plants at one time. For some plants, such as
orchids it is highly desirable, if not essential - but not cacti. The argument in favour of
an occasional fine spray is that some cacti grow in areas where there is a wide swing in
temperature which causes heavy dews. It seems that cactus spines are quite adept at
capturing such moisture.
Last, but not least -
Keep in mind there are pots, and pots, and pots, and that a fourth type of pot which appeared
recently on the scene is ceramic and often highly coloured. It is claimed to be de rigeur
and is said to be a colourful difference between British and USA shows.
Third in that row of pots is the ubiquitious plastic pot which now dominates our gardening
activities. It is far from ideal because it is too thin, heats up in sunshine too much baking
the roots of plants which would not happen so much in the wild, and it cannot breathe. Also,
it cracks readily especially when exposed to sunlight.
Second in the list are modern clay pots but first in the list are old Victorian or Edwardian
pots, many of which were hand-made.They can often be obtained at country sales, and usually
show an uneven surface on the inside, and even outside on some.
The advantage of a clay pot is that it can breathe. This lets air into the root system
similar to natural conditions. One disadvantage is that when they dry out roots may cling to the sides of
the pot to take up the moisture in the air which percolates through the pot wall. Clay pots
are probably at their best when plunged.
The other essential aspects of a plants' environment are
compost and watering.