It goes without saying that every type of cactus needs an individual approach. So in order to water your cactuses properly, you should take into account a number of factors. But all in all, the following cactuses require more watering:
1. Hygrophilous cactuses
2. Growing cactuses
3. Cactuses with big roots
4. Cactuses in earthenware pots
5. Cactuses in sandy soil
6. Cactuses kept in high temperature and dry air
And, on the contrary, you should be careful with watering of these cactuses:
1. Xerophilous cactuses
2. Cactuses that are at rest
3. Cactuses with small roots
4. Cactuses that are grown in plastic pots
5. Cactuses clay soil
6. Cactuses kept in low temperature and humid air
In summer I water my cacti just like the other houseplants – just when the soil gets dry, except cool rainy days. In autumn watering should be reduced gradually, and in winter it should be stopped at all – to make dry and cold wintering for your prickly friends.
It’s better to use rainwater, but you can use tap water settled for a day or two. It must be warm – about 30-40 C°. If you put a hand in water with such temperature, you will feel neither warmth nor cold. I seldom use water of room temperature, especially when it’s cool outside. The fact is that cactus roots can’t absorb water, which temperature is lower than 10-12 C°. If it’s about 20 C° in the room, the soil in the pot is colder. The temperature of the water you poured out on this soil slumps. And a cold, moist soil is extremely dangerous for cactus roots.
The best time for watering is in the evening in summer and in the morning in winter. The water should not get on the stalk of the cactus plant, watch it carefully. And remember that every cactus can bear lack of water, but its excess could be baneful.
On the other hand, a lot of cacti suffer just from water shortage in hot summer days: many collectors don’t know that cactus absorbs only a few percents of water together with nutrients dissolved in it. The rest of water is used for the cooling of the stalk through evaporation to protect it from overheating. Water shortage in hot summer period is very harmful.
Hot days and cool dewy nights are typical for the most regions of America where cacti grow. Dew and fog can be replaced by spraying, that has an excellent effect, if you meet some simple conditions. For my collection I stick to these rules:
1. Never spray cactus, if the weather is cool and damp – the stalk may begin to rot.
2. Use a small sprayer that pulverizes water to fog, but not to big drops.
3. Use only boiled and hot water, because its temperature stumps during spraying.
4. Hygrophilous cacti that have leaves, for example Christmas cactus, like not only sprinkling, but also warm shower. It’s undesirable to spray your cactus late at night because of a quick temperature drop.