Which day time and night time temperatures are best suited for cacti.

[Russell99]

It's been a long time since I'm posting here again. I stopped my hobby for quite some time due to my mental health and I'm planning to start it again. During the break I've noticed that my cacti would get sick very often and some seemingly healthy cacti would unexpectedly start rotting. My cacti would always get infested with pests and fungi if I don't apply pesticides, fungicides regularly. I think the cause could be the temperature in my area. The temperature is pretty constant about 27c-30c day and night. I think it's the temperature that's the issue here because I recently went on a trip to the Highlands in the country and noticed many cacti flourishing there, they were just potted in the normal dirt there and all of them were really healthy. The temperature there were 13c—18c at night/18-24c during the morning and afternoons. The area is at a elevation of about 1000-2000m absl.

So what do y'all think. I think that it's the temperature issue with me as most cacti get a natural winter rest in their habitat and mine don't which results in them being unhealthy. The only cacti that are doing best are a few melocacti and frailea species.

Please do correct me if I'm wrong with my statement here.
Thanks!

[7george]

I think you are right about your assumptions. Preferred temps depend on the species and its origin. For most "desert" cacti maybe day-night amplitude should be around 15 - 20 C and so is in dry temperate places but varying much with the seasons. Living in tropics you better grow more tropical species that adapt better to your climate.

Look at the weather websites to see fluctuations in different places.
https://www.wunderground.com/forecast/a ... .79,-65.41
https://www.wunderground.com/forecast/c ... /ICALGA221

[One Windowsill]

Some Frailea are from Brazil and Colombia. Melocactus are pretty much entirely tropical.

Unless you are going to set up a controlled environment chamber with reduced humidity and temperature or move to the Highlands you do need to concentrate on those tropical species. Even many of the Mexican and Caribbean species are from the mountains and don't like constant heat.

Have you thought of south Asian succulents like Caralluma, Ceropegia, Boucerosia, Frerea and Sarcostemma? There are other families as well, like Cissus, Euphorbia, Jatropha and Kalanchoe.

[abhikjha]

I kinda disagree. I am in similar climate as yours (in Mumbai, India). All my cacti are doing pretty well. I have lots of Astrophytum, Gymnocalycium, Ariocarpus, Obregonia besides Discocactus, Melocactus and Uebelmannia. I am growing tons of Ariocarpus and Lophophora and Pseudolithos as well from seeds.

There are lots of growers in India, Thailand and in Singapore who have been growing almost all varities of cactus since generations. Climate of all these countries are mostly similar.

Few things I learnt which may be helpful in your case:
1. Soil mix - I changed it completely to Pumice and Cinder. No craps like soil, sand, compost. It really helped. Few gymnos immediately flowered when I changed the substrate.
2. Watering - I don't water them (or once or twice in dry patches of 10-15 days) in rainy season. They are brought inside near windowsill and fan is on 24 hrs for air circulation. Air circulation is perhaps the most important thing after soil and watering.
3. Fertilization and pesticides - since I grow in mineral substrate, I fertilize them with every watering except in monsoon when I water which is once or twice, I use systemic fungicide. I also use imidacloprid once or twice in the sunny weather.

Cactus are very modest plants in my view. If you see the FB profiles of gardeners in Singapore, Thailand or in India, you will understand what I am saying. They don't only grow in our climate but thrive if basics are right.

[HudsonLH]

Russell,

I believe george and one windowsill are Western growers and so their views on cultivating cacti in the tropics are solely academic.

Regarding your temperature concerns: while it is true that CAM occurs best at temperatures from 10C to 25C, it is also very clear that cacti are able to acclimate to a large range of temperature differentials. Please see: (https://link.springer.com/article/10.10 ... 013-9874-6). Drop me a private message for the PDF if you are not able to bypass the paywall. Practical proof of this can also be seen in many Thai and Malaysian nurseries where many spectacular specimens of supposedly desert cacti have been grown from seed. A quick search on google or youtube with the search terms "thai cacti" should bring up many results.

Regarding winter rest, very few succulents or cacti require dormancy to thrive. Flowering obviously suffers, but health will otherwise remain undisturbed.

If there is good ventilation and the substrates are adjusted to fit your environment, I believe fungicides are only necessary come the rainy seasons. Systematic pesticides should always be applied consistently every few months - there is no workaround for that.

H