Discocactus  
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General
Sow
Where to sow
Grafting
Seed harvesting
Storing seed
Labeling
Watering
Cultivation climate
Growth season
Diseases
Importing

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 Climate-conditions.

The greenhouse position and glass condition
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.

Heating
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 follows:
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 failure.

Ventilation
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.

Copyright 2003

email: Piet van der Laken