I’ve heard it has something to do with conditions, but this seems counterintuitive since the desert conditions are much harsher (hotter, drier) than those in my house, so if anything you’d think it would require less water.
In: Biology
Part of it has to do with how humidity and heat work when the sand/soil is in a huge mass. Deserts get very hot and dry, but it’s only the top layer which really catches the worst of the heat. A few meters below the surface, temperatures stay much more moderate through the day and night cycle, and the dryness is not so extreme. Residual water from rainfalls is retained down here a lot longer, and there may also be some groundwater reserves that it seeps up from. Most of the time even in a desert, there is always a *little bit* of moisture working its way up from a more humid layer towards the surface thanks to capillary action and evaporative cycles. It’s not *very* moist, but there’s a whole ton of it by mass, so it takes a long time to exhaust.
Your potted plant is just in a little isolated clump of soil, surrounded on all sides by air. [And the smaller the pot is, then the greater its surface area is, relative to its volume.](https://en.wikipedia.org/wiki/Square%E2%80%93cube_law) When the water in that clump of soil is exhausted, that’s it, it’s gone, it doesn’t have any deeper, moister neighbouring soil to sponge from. But if you tripled the size of the pot your plant was in, you would have to water it 3 times as heavily to reach the same soil moisture level, but thanks to the squared-cubed law linked above, it would take a lot longer to dry out.
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