BCSS - Forum

Is there a maximum temperature beyond which cacti seeds will not germinate?

The reason I ask is that I have a non-thermostat propagator and on putting a max-min thermometer in discovered the temperature was occasionally reaching 95F. I have 36 individual square pots in there, of which 7 have so far germinated after 10 days, but i thought maybe the high nineties might be a bit excessive for certain types.

If they have been subjected to "too high" temperatures is it worth shifting them to a temperature regulated propagator at 75 to 80Fish or will the seed have been destroyed?

There are over 1,000 species of cactus. Which ones were you thinking of?

They are a mixed bunch:
Ariocarpus
Aylostera
Aztekium
Copiapoa
Coryphantha
Discocactus
Escobaria
Echinopsis
Parodia
Ferocactus
Frailea
Lophophora
Melocactus etc.

None of them will be damaged at 95F, but some will almost certainly not germinate if kept at that sort of temperature, even just for a few hours of each day.

For those that don't germinate within a couple of weeks, drop the temperature. Try to drop the night temperature in particular. 75F - 80F during the day is a good figure, but if that still isn't good try dropping the night temperature to 60F or even cooler. Aylostera seems like one that would prefer a cooler temperature, but possible also the Escobaria, and maybe Echinopsis and Parodia depending on which species.

Thanks for that Ian. This was a "spare" propagation unit I am using and I must admit I did not realise how warm it got in there! I will give them a week and move them to a better controlled unit if I don't get germination.

Did the Melocactus germinate? They're a group where most at least are supposed to germinate well at high temperatures? I don't know because I've never grown them. Same for Frailea. I do find that Ariocarpus germinate well at the high end of the temperature range, althoiugh they can still be slow.

So far in these conditions these have germinated:
Cochemiea poselgeri
Copiapoa coquimbana
Coryphantha vivipara
Echinocactus parryi
Eriosyce esmeraldana
Frailea cataphracta
Gymno riojense
Lobivia aurea
Lophophora lutea

Ariocarpus, Aztekium, Copiapoa, Discocactus, Frailea, Lophophora and Melocactus probably appreciate the high temperatures more than any of the others on that list. Ariocarpus, Aztekium and Discocactus especially love really high heat.

CactusFanDan wrote:Ariocarpus, Aztekium, Copiapoa, Discocactus, Frailea, Lophophora and Melocactus probably appreciate the high temperatures more than any of the others on that list. Ariocarpus, Aztekium and Discocactus especially love really high heat.

I bet the Aztekium germinated already and you just can't see them

I copied these tables out some years ago:-
As you can see high temperatures can inhibit germination if much above the optimal temperature. 25C mentioned as the mean temperature = 77F. As Ian says cooler night temperatures mimicking day and night fluctuations in habitat can often be beneficial.