Dormancy

[JRL]

What is the trigger for dormancy and for the active growth stage of trichocereus sps.? Is it average temp, low temp, length of day?

Is it the same for lophs?

[CJ]

Something i`d like to know also,what the trigger(s) in it`s natural setting... that kind of thing always interests me. trout`s book is more of an ID manual...

[laughingwillow]

I'm guessing its ground temps coupled with shorter days and decreased precipitation. But ground temps are prolly the trigger, imo.

lw

[EA-1306]

I don't know but can speculate. Some of Park S Nobels work might contain some information on this topic as well.

I think that it is related to temperature, however in my own experience the plants seem to grow very slow when I put them into dormant conditions. I have over wintered them for about 8 years now and use a combination of a lack of water and cool temperatures to prevent them for growing much at all when they are being over-wintered. I have also grown them with light right through winter and think that dormancy is not as big an issue with them as it is with Ariocarpus cacti and allies.

In nature the plants are found so close to the equator that I hesitate to suggest that photoperiod is a major factor.

[laughingwillow]

Good point, EA.

lw

[visionarybear]

how natural is dormancy actually?
i mean in its natural habitat, does it have a dormant period or is this an induced factor of trade to other parts of the world with different environmental changes?

it makes evolutionary sense for a plant to develope that will retain life even when resources arnt availible, hence if you stop watering, no water is available to increase cell volume and therefore mass, and if you stop light, then no photosyntesis can take place and thus no growth can occur. if its cold, cellular processes slow down, but wont stop, just very slow growth...

so in the wild, 'dormancy' would be the result if resources, any of many, were not availible. on the flip side, my cacti grow all year round outdoors here in new zealand with no worries...

[winder]

Based on comments I have heard from a past president of the CSSA, some cacti REQUIRE a dormant period before they will bloom.

So now my speculation....

The equatoriallly native Trichocereus species probably do not require a dormant period, whereas those from further south, Bolivia and Argentia, probably would benefit from a dormant period.

In equatorial regions where some of these cacti originate, the length of day and the seasonal temperature do not vary by much, so dormancy would not be expected to be a normal phase and although tolerated, may not be a necessary part of the life cycle.

In North America, such as Nevada and Arizona, which are located well outside the tropics, shorter daylight and considerably cooler temperatures do certainly occur; therefore dormancy would be expected to a normal part of the cacti life cycles in these regions.