Are you going to water your cacti

[Nick_G]

Are you going to water your cacti during the upcoming hot weather? I think it's a complete waste of time, they just shut down when night time temperatures are in the high teens and above. It seems counter intuitive but I believe it to be true.

40C forecast on the BBC weather app for Southend on Monday, surely not. The Met Office forecast 30C, the truth is normally somewhere between the two.

[Cidermanrolls]

The mature plants, probably not.
The trays of seedlings, yes.

[el48tel]

I am with Cidermanrolls on this. Been doing this with seedlings for a few weeks.

[Tina]

All my cactus house watered & I'm even thinking of putting up the green netting for a while, I have only just stopped shutting them up every night, my plants are pampered or it could be cooked

[Chris L]

I am going to give them a drink after it has cooled down.

[Smel]

Hi,
I tend to water late in the day, as the Sun is going down. This gives the water time to reach the roots? and the plants time to take it up, but it may not work that way.

Mel.

[Nick_G]

Hi,
I tend to water late in the day, as the Sun is going down. This gives the water time to reach the roots? and the plants time to take it up, but it may not work that way.

Mel.

I believe that it is high night time temperatures that cause cacti to shut down, not high day time temperatures, so it wouldn't make any difference what time of day you water your plants. The optimum growing conditions are high day time temperatures and low night time temperatures. Happy to be corrected though.

[KarlR]

Not saying i necessarily disagree, but how do you explain cacti growing in the tropics or regions just north and south where night time temperature will be above 20C for large parts of the year?

A quick Google search for average night time temperature in e.g. Brazil gave an answer of minimum 15-17C in the night (apart from the southern part of the country where it can go lower). So logically it'll be above this for large parts of the year. The same will likely be true for the Caribbean and the parts of Mexico bordering the Gulf.

I have read about how cacti can shut down growth with high night time temperature, but I can't remember where I read it or if there were any caveats or if it only applied to certain regions. It seems more logical if it were to apply more specifically to areas where average night time temperature doesn't regularly go above 20C.

I believe the likes of Sclerocactus and Pediocactus go dormant in summer (at least in habitat), but I don't know if this is down to night or daytime temperature or something else. Other cacti growing alongside them do not go dormant I think.

[Nick_G]

Yes, that's true Karl, I can't explain it. Maybe it's only cacti from high altitudes, but I'm convinced for the cacti genera I grow there are two growing seasons, spring and autumn with some growth in the summer when conditions are favourable (cooler nights).

[KarlR]

You may we'll be right, Nick. It certainly makes more sense for high altitude cacti to react to high night time temperatures. Here in Norway we almost never get night time temperatures above 20C. So far this summer the warmest it's been in the night was 18C, with 12-15C the most common range.