|During this month even less cacti are flowering and even more gradually stop growing. So, watering should be done with caution and care should be taken for the cold sensitive cacti.
This month where temperatures are lower and humidity is usually higher, watering of the cacti should be done with great caution. Above all it is most important to provide protection from rain, since this month is usually a rainy month in Greece, and it is a parameter that cannot be controlled in means of quantity of water that cacti receive and also the frequency of the rain. Combined with the high air humidity, the soil that remains wet for long can lead to fungus and consequently cacti will develop rot and die. However, compared to colder areas of the world, here in Greece, this can be a relatively warm month, at least the first half, so, it is useful to water cacti during this month. One useful rule that I follow is based on the highest temperature of the day: when day temperature is approximately near 20 C for a few sunny days and when weather forecast is the same weather for the next 4-5 days, I water. Overall, this month I water 1 or 2 times.
Of course, other factors should be again taken into account as well, like special weather conditions. For example, in locations with higher elevation temperatures can be lower. Another factor is definitely soil composition (water restraining soil etc.). Water should be completely dry before watering again. One more factor has to do with the cactus species that one grows. This month, some cacti are flowering and they need more humidity. Also, some cactus species are growing during this month, like, for example columnar cacti (pachycereus, cleistocactus, pilosocereus azureus, myrtillocactus, carnegiea etc.) but also globular cacti like neoporteria, copiapoa, melocactus and others, and, therefore they need to be watered too. Finally, notocacti need at least 1 or 2 waterings during this month.
The above are true for the climate conditions here in Thessaloniki and for the specific location of my cacti regarding sun exposure etc. It is useful for everyone to observe his/her own plants and adapt these guidelines according to local weather conditions and cactus species.
The lowest night temperatures of this month are the signal to move cold sensitive cacti inside the house. So, when weather forecast is for temperatures below 15 C, it is usefull to prepare a location inside where cacti of the genus melocactus and discocactus can be moved. A bright location close to a window is the spot I found in my living room, where they have direct sun for a few hours. On warm and sunny days, when I am home, I put them out for a few hours and bring them back inside for the night. For the rest of the cacti the great variation between night and day temperatures seems not to harm them, they like it and this way they get gradually used to the approaching colder temperatures of the winter.
If no treatment of pests was done during last month, this month is the "last opportunity" to do it. From now on it will be harder to treat cacti because usually treatment is done with the use of water, and the weather from now on will be colder and humidity higher. So, a decision has to be made: if it seems highly possible that spraying of the cacti will lead to rot (because of low temperatures), it is best to isolate the affected cacti from the rest of the collection. If treatment requires one application (watering or spraying) it can be done on some day with good weather and with good weather forecast.
Cacti flowering now:
Mammillaria polythele, mammillaria polythele var. nudum, mammillaria schiedeana, mammillaria plumosa, thelocactus setispinus, matucana madisoniorum and others