Know what it is? Water them at night. Really. Ready for a biology lesson? Well, botany lesson, to be more precise. Here goes. Pay attention.

Woody Minnich, shown here with my friends Hellen Adrian and Sheila Stevenson when we attended the the 2012 Albuquerque cactus show and sale, gave a presentation at this year’s CSSA Cactus and Succulent Convention titled Secrets of Growing Quality Cacti and Succulents. He assured us it really wasn’t a secret, but just a principle of biology that most people don’t know, and that I certainly did not know, which is that cacti and succulent plants are CAM plants, CAM being an acronym for Crassulacean Acid Metabolism.

And what does that mean? According to biology online, it is-and here is where you need to listen up-a CAM plant is one that utilizes the Crassulacean acid metabolism as an adaptation for and conditions CO2 entering the stomata during the night is converted into organic acids, which release CO2 for the Calvin cycle during the day, when the stomata are closed.

Got that? Here’s more. CAM plants utilize an elaborate carbon fixation pathway in a way that the stomata are open at night to permit entry of CO2 to be fixed and stored as a four-carbon acid. Then during the day the CO2 is released for use in the Calvin cycle, which is a cyclical series of biochemical reactions that occur in the stroma of chloroplasts during photosynthesis, causing sugars and starch to be produced. In this way the rubisco is provided with high concentration of CO2 while the stomata are closed during the hottest and driest part of the day to prevent the excessive loss of water. CAM plants are therefore highly adapted to arid conditions.

CAM plants often show xerophytic features, such as thick reduced leaves with a low surface area-to-volume ratio, thick cuticle and stomata sunken into pits.

Like cacti and succulents.

Now-the short version from any plant that undergoes a form of photosynthesis known as CAM, in which carbon dioxide is taken up only at night.

And photosynthesis is what makes your plants grow and bloom.


So, all of this is to say, water your cactus and succulents at night for optimum growth potential. Just because watering in the evening has always been a better fit for our schedule, it turns out my cactus have benefitted, and I didn’t even know why.

Just watering at night may seem too simple and easy to be true, but trust me, Woody knows what he is talking about. So give it a try with your plants.

And if you want to learn more of the technical stuff so you can amaze your friends and impress your enemies, read more at these websites: