How Do Succulents Hold Water?
by Lynn KirkNov 2, 2021
Succulents retain water because they made special adaptations over time. That makes sense because if you lived in the desert, wouldn’t you have to make a few adaptations, too? This fascinating group of plants made modifications in their structural features, as well as their biological mechanisms, in order to survive in their native environments. Most of those native habitats were either arid with high temperatures or regions with rocky soil that can’t hold water. As a result, many of the succulents’ alterations dealt with water retention.
So exactly how does a succulent hold water? Here are 7 ways that succulents hold water in easy-to-understand terms:
1. Wet tissues. Succulent leaves and stems have sponge-like tissues that can retain extra water until needed. That’s why their leaves and stems tend to look plumper or “fleshier” than those of other plants. In fact, the fatter the leaf, the more water it can potentially hold for future use. Similar water-retaining tissues also are found in succulents’ roots. Fun fact: Biologists have recorded up to 2,000 pounds of fluid in a saguaro cactus!
2. Round, not flat. Most household plants feature flat leaves, but not succulents. Instead, succulents’ leaves are typically rounded. This spherical shape reduces the overall surface area exposed to the air, and less exposure equals less water loss. That's also why some desert succulents often have no leaves at all! Instead, they might sport thorns (spines) that typically are small in comparison to the plant’s overall mass. These spines keep predators away, plus they create a tiny bit of shade that helps reduce water loss. After all, every bit helps!
3. Wax sealed. Any loss of water is critical when there’s little moisture to begin with. Fortunately for succulents, a waxy film covers their leaves and stems. This natural coating is often described as hairy or spiny. Regardless, it not only seals in the plant’s water; it reduces evaporation.
4. Shallow rooted. In areas with flash floods and rocky soil, a plant has to respond quickly in order to benefit from the short-term water supply. Succulents’ roots are shallow enough that they can quickly absorb groundwater before it dissipates or flows elsewhere.
5. Night worker. Succulents take in carbon dioxide for photosynthesis through stomatas, which are tiny pores on their leaves. When these pores are open, there’s some water loss through evaporation and transpiration. To help lessen surplus moisture loss, succulents learned how to delay the first step of photosynthesis. Instead of opening their stomatas during the day, they open them at night when chances of water loss are less. They take in the CO2, store it as malic acid, and then covert it back to CO2 for photosynthetic processing the next day, when the necessary sunlight is present. This process is known as crassulacean acid metabolism or CAM. Another point to note: Succulents tend to conduct photosynthesis through their stems, not their leaves.
6. Less is better. Another cool point is that succulents have fewer stomatas than their non-succulent peers. Having less openings is better because there’s less chance for losing another iota of precious moisture.
7. Thick skinned. The more layers you wear, the less sun exposure you’ll get. That same principle applies to succulents. Their thick skin (cuticle) gives them an extra coat of protection against the sun and extreme water loss. Fun fact: All these adaptations can cause a succulent to go without water for one to three months, depending on the species.
In addition to learning how succulents hold water, now you understand why too much water can be deadly to succulents. Knowing when to water isn’t easy, but here are two tips. (a) Watch for changes in the succulent’s leaves. If they start to become dried and shriveled, they may need more water. (b) However, since other factors can cause the leaves to shrink, you might want to doublecheck the soil. Stick your finger into the top inch of soil to see if it’s dry that far down before you re-water.
If you happen to overwater (which most of us do at one time or another!), your plant might recover — if there’s no sign of rot or disease around the roots and stems. Let the plant dry out for a short time period and see if new growth starts to appear.
Two more water-related reminders. (a) Always use modified succulent soil. (b) Select container pots with holes in the bottom so there's sufficient water drainage.
This water-wise report is brought to you SUCCULENT MARKET, America's most experienced grower of domestic succulent plants.