Where the light conditions are right for cacti, they do well. Most species are true sun worshippers, and they like it warm. By the way, they easily cope with strong temperature fluctuations between day and night, as they often occur under glass. During the summer, succulent plants find optimal conditions in a greenhouse or cold frame.
However, depending on the glazing material used, they do not always get enough light. Polycarbonate covers in particular can become cloudy over the years. In addition, polycarbonate and other plastic coverings let in little or no UV light, which promotes the species’ own compact growth. So how do you create the ideal light conditions for cacti?
Optimum lighting conditions for cacti
Glass as well as web double panels made of special Plexiglas (Alltop) allow the full light spectrum available to plants to pass through. They create the right lighting conditions for cacti. If your greenhouse is covered with other materials, it is better to put the prickly creatures outdoors in summer and bring them back into the greenhouse from September onwards, as soon as wet and cool weather threatens.
Here behind real glass, the light conditions are right for cacti. They grow beautifully compact and develop an intense green colour. The thorns also become stronger. In such greenhouses, which are also well ventilated, they can spend the whole summer.
Leaf and arrow cacti
For leaf and arrow cacti, such as the Christmas cactus, good light conditions can be provided by keeping the cacti in the greenhouse only in spring and autumn. In summer, they do well in a bright spot with only intermittent sunlight.
Getting used to the sun
Slowly accustom cacti and other succulents to full sun. For the first one to two weeks, it is better to place them in partial shade so that they can get used to the new light conditions.
The light green new growth on this notocactus is in danger of burning if exposed to too much sunlight.
Poor light conditions for cacti
What happened here? If cacti sometimes grow thin and then thicken up again in a manner typical for the species, they have not received enough light at times, usually during overwintering in warm living rooms. The ideal light conditions for cacti are created by overwintering them in a cool room at 5-10 °C. This prevents them from becoming yellow and thickening. This prevents them from becoming yellow and helps them retain their typical shape.
By the way: Cacti that are kept in a cool place during the winter will flower particularly abundantly the following season.