This topic deserves its own thread.
I can add my observation: all my cacti with small areoles are quite potent. I have only one with bigger areoles, so far not tested, but I am going to do it in near future.

Ok, but what is the distribution of small/big areolas? Is it 50/50? E.g. if there is 80% of small areolas in the population, then it is likely strong cacti will have small areolas with higher probability. Any idea?

It will be interesting to see how macrogonus measures up on the potency scale as it has large areoles. So does terscheckii. That said, there's no way my specimens of these two species are going anywhere near a knife - they're far too pretty! We'll have to wait until I get my specimens to flower & set seed. The macrogonus seems likely to be sooner (within the next decade). I'm not sure if I'll live long enough to see the terscheckii flowering.

Regrdless, I'll still give heavy consideration to cutting an areole or two off these specimens in order to propagate some more. The areole grafts have been rather inspiring, pete!

Pete it varies by species. All the Bridgesii and Scopulicola I've seen have small areoles. With Pachanoi there is some variety but most have small areoles. With Macrogonus there is variety. With Peruvianus there is some variety but most have large areoles. All the Cuzcoensis I've seen have large areoles.

Thats what got me thinking about this in the first place. The more active types generally have small areoles.

Doubledog is right, I should start a separate thread for this. I dont want to hijack your thread Pete. But I thought you would be interested in this observation. I'll try to start a separate thread for this soon.

I have one like this too. It took me eight years to get it to root.

Looks like they might even be from the same mother plant!

Well, this procedure has two milestones. The first milestone is taken graft (seems we are here atm). The second is puping. I've got BAP in lanoline, so I might help it a bit, but I just wanted to see how long it takes to pup on its own (whether it does pup).

If you would like to take areolas from uncut plant, then leather punch seems to be better way how to make prepare the scion.

Are you serious downwardsfromzero? It had to dry off by that time, no?

As I said, I will check it in the future. But I would love to have some sign that would allow to identify potent specimen even within one tricho type. But unfortunately there seems to be none

Thats why you bioassay or test via extraction. But it helps to start from a pool of plants that are good and not to waste time on types that are unlikely to be strong.

Pete,
Another topic related to this discussion: Do you know about CAM photosynthesis? CAM stands for Crassulacean Acid Metabolism and is how cacti and sedum photosynthesize differently than most other plants. In order to conserve water, instead of respirating during the day, they fix their carbon dioxide at night so that their pores(stomata) can remain closed during the day, conserving water.

The nocturnally obtained CO2 is converted to — malic acid! which is stored in the cell's vacuoles until the morning. During the day when photosynthesis takes place, the organic acid product of nighttime CO2 uptake is then decarboxylated back into carbon dioxide and the energy in sunlight is used to convert the CO2 and water to sugar and oxygen.

An interesting side effect for our discussion is that CAM plants taste sour at night or early morning, and sweet or bitter during the day! So even the time of day has an effect on the taste.

The opening of the stomata is triggered by darkness and cool temperatures. I have read that cacti require temps below 70F or 20C to trigger the pores to open. This occurs naturally in deserts and high elevations where our cacti grow.

A problem occurs when trying to grow them in temperate regions. Indoors or during the summer, nighttime temps may not get low enough for the pores to open. The plant keeps growing but cannot photosynthesize so the new growth is brown and what we often refer to as "sunburn". It happens here in July and August, and also happens under lights indoors. The plant cannot make sugar for food and is literally starving. This is a problem for me every summer and I have to move all my cacti out of the greenhouse because it stays too warm in there at night.

In the fall when nighttime temps start to drop again, my "sunburned" cacti recover. I don't know what effect the summer stress has on mescaline production, but I assume it can't be good because it is commonly known that they get more potent during the winter when it is colder and darker and they are busy storing more malic acid rather than growing. My plants grow beautifully in the Spring after a long period of cold temps—plenty of malic acid has accumulated.


There is tons of info on CAM on the web but I thought you would be interested in this article:

Why Do Cacti Taste Bitter in the Afternoon?

Side project — I have been thinking of augmenting my soil with malic acid during the warmer months. I wonder if the plants can utilize it from the soil? Or perhaps a foliar spray at night?
And would a malic acid soil additive potentially increase potency?

Foliar Sprays of Citric Acid and Malic Acid Modify Growth

I'm pretty sure that cacti can turn CAM photosynthesis on and off depending upon the weather. Cacti can still perform photosynthesis during hot weather. What you are seeing with those plants in your greenhouse is probably heat stress.

I don't think so. That was what I thought initially, so for the past 2 years I've been using shade cloth and an evaporative cooler to keep the temps in the greenhouse comfortable during the day. But come July and August the brown still returned. It is only by putting them outside the greenhouse at night that the brown is eliminated or reduced.

Also, they exhibit the same behavior under lights indoors where it is never hot, but the temps don't drop at night. I can grow them under lights without damage for a while if they've been exposed to cold temps recently. In order to prevent the brown under lights I have to cycle them into some cold storage for a while. I have noticed that cold really helps to "harden" them and that they grow much fatter when they are exposed to periods of cold.

I have never heard that cacti can turn CAM on and off. I have always heard that they require a period of darkness and cool nights to function properly.

UPDATE: There are obligate CAM plants such as cacti which use CAM exclusively, and facultative CAM plants which employ the optional use of CAM photosynthesis, typically under conditions of drought stress, in plants that otherwise employ C3 or C4 photosynthesis.

See here and here.

Yes I think you're right about that. Trichos can only perform CAM photosynthesis. My bad. For some reason I thought they could also do C3 under certain conditions.

I had never considered this as a cause for stress in hot weather. I live in a hot desert climate. Here the Trichos keep growing through the summer but they need shade through the hottest time of day and regular waterings. Are they just growing off of stored reserves? During summer the nightly low temps are often in the 80's.

It is the combination of high day time temps and full sun with no shade that seems to really cause stress and damage to the Trichos. In a greenhouse if the daytime temps are too high and there is no shade it will stress them. In hot weather they need shade during part of the day or they will turn yellow and stop growing. But with afternoon shade they stay green and continue to grow.

Yes, I know about CAM photosynthesis. Though I don't have chance to go lower with night temps bellow 20C, I don't have any mentioned problems of brown color and the cacti grow quite well. But of course they might grow even better if I managed to keep the temps lower overnight. Unfortunately this is not possible.

But I can confirm, that the same grafts grow fatter bellow the sun, even when the whole day light income is less than when grown indoors. Question is whether this is because of more intense light (though in short periods compared to indoors) or something else like lower night temps.

It could be a combination. There is no way that indoor light can ever approach the intensity of sunlight. It also cannot match the full spectrum of the sun, no matter what bulb makers claim. But I have found that the combination of cold night temperatures and sun are what really makes them grow more fat and stout, while indoor lights make them thinner and taller.

I have another source-less comment for the record: I believe I remember reading that Trichocereus seedlings use C3 before switching to CAM permanently. This made sense to me at the time considering how differently seedlings can be treated compared to mature cacti (humidity etc.).

Yes I have also heard that Tricho seedlings are able to perform C3 for the first year or two. But I dont know enough about the science to say for sure.

But ultimately I just dont think that CAM is a limiting factor in cacti's ability to grow in hot weather. These are, for the most part, desert plants that thrive in some of the hottest climates. I'm not sure how the details all work out, but either they are still able to photosynthesize during hot weather or they are able to store up enough energy reserves that it doesnt matter.

Regarding Trichocereus specifically, they grow at high elevation in their native range, and the summer high temps are generally mild. Trichos do not do well in full sunlight when the temps go to the 90's and above. They will survive, but they yellow and slow down in growth. But with shade during the afternoon hours they stay green and healthy and continue to grow. In places with cooler summer weather all of this is not even an issue.

Arid climates are hot, but since there is little cloud cover or humidity to trap the heat, the temperature drops at night. Sand cannot hold the heat for long, it gets cooler as soon as the sun sets. Cacti that thrive in hot arid environments have evolved to utilize CAM within this temperature range.

As you noted, Trichs live in a very different environment than normal desert cactus. In Matucana Peru, for example, the daytime highs average in the 70s and the temperature dips to around 40 at night. Since they are near the equator, the climate doesn't vary that much and the days and nights are roughly equal in length all year long. These cacti have evolved to be happy in this environment which is very different from a lowland desert.

In the northern areas of the USA at the peak of summer, the days are very long and the nights are short and there can be stretches of very hot and humid weather for several days in a row. When that happens here, many of the trichs will develop some bands of brown growth, even when grown under shade cloth. The only way to prevent it then is to move them into deep shade where they don't get as hot.

Everyone will have to find the conditions and microclimates that work best for their location. Regarding CAM I think that the 70F cut off may not be totally accurate. If we look at the monthly averages for a city like Phoenix we see that 4 months out of the year the average low temps are above 70F.

https://www.rssweather.c...climate/Arizona/Phoenix/

And yet many different kinds of cacti are grown there and thrive, especially when irrigated and fed in landscape settings. I find it hard to believe that for the 4 summer months those cacti are unable to photosynthesize, even though they are growing and flourishing in people's yards during that time, not to mention that cacti grow in the wild all around that area.

Maybe this topic deserves its own thread?