The results of
care taken during cultivation
Photo from the
collection of Piet van der Laken
Supposing that we have already some experience with the
greenhouse culture of cacti, we will give you a quick review of the most
important criteria. The following advises are valid for north European
The greenhouse position and glass
In the months of February, march, October en November we should take as
much advantage as possible from the sunlight and keeping the windows
(glass or other material) clean is evidently a must. Easy movable screens can lower the heating costs considerably and may reduce the light
and temperature during hot days. Between these screens and the glass we can
stretch an extra crystal clear insulation film which will stay in place
from the end of November till medium April. This will improve the climate
in the greenhouse and prevents a sudden temperature change when we open
the screens. It is also advisable to insulate the floor to keep the cold
but most of all the humidity out. The greenhouse must be able to receive
sunlight for minimum 5 hours
per day preferable the morning sunlight.
Every type of heating is suitable providing there is an outlet for
the smoke/gas. Do not use the so called 100% burners without outlet.
There is much damage caused by these heating systems, these damages show
very often in springtime. A full or half automated temperature control is
not only easy but also less energy consuming. The temperature control
steps should not be bigger then
0,5oC. The needed capacity of the heating can be calculated as
Kcal/h = square glass area x 6 (transmission coefficient. for glass) x
temperature range in oC.
I.e.. with a possible temperature of minus 20 degrees we should still be
capable to maintain a temperature of 15oC therefore the
capacity need to cover a range of minus 20 plus 15 = 35oC.
Bottom heating is required for Discocacti on their own roots,
whereby we maintain the temperature at approx. 18oC. Grafted
Discocacti don't require bottom heating. The disadvantage of
bottom heating is the fact that nematode (eels) will profit from the
warmth and multiply themselves. A good temperature alarm should be
installed operating with a backup (batteries) power supply incase of power
It is not easy to maintain a stable climate in a relative small
greenhouse, especially in spring with changing cloudiness. Ventilation is
necessary to prevent excessive high temperatures (more then 35oC).
Ideal is a fully automatic ventilation system whereby the windows on
leeward side are aerated in a modulated way. There are very good systems
available, but also tagged with a high price. A
handy amateur could create a reasonable working system with relative low costs materials.
It is important to preserve the plants from big changes in temperature and draft.
Movement of the air
in the greenhouse is very useful. It concerns here only the movement of
the air in the greenhouse without addition of fresh air from outside.
Draft is movement of air coming from outside with other specifications, in
temperature and humidity, then that in the greenhouse. This phenomena will
never occur in nature and there is no plant who will not succumb after a
while in draught. When the temperature difference between the
inside and the outside is bigger, then the risk of draught becomes higher. Therefore a
carefully ventilation is, especially in springtime of utmost importance.
Light and humidity
Contrary to the above mentioned factors and many others, light is a factor
we can't control. We have to accept what the sun on the northern
hemisphere has in store for us. Artificial assimilation lighting could
positively influence the plants during the months with low lights, but the
gain for our light loving plants is negligible. Much light does not only
mean heavy spines but means also a better physical condition and hence
more resistant against diseases and plagues. The months December,
January and February we therefore use to give the plants a rest by
stopping to water the plants in October. Humidity is an easy factor to control, it
suffice for our purposes to keep the floor wet during the spring. In the resting period
a low humidity is desirable. Keeping the environmental temperature on
approx. 15oC will take care of this.