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Looking for Solutions to the Water Riddle for Plants

Friday November 09, 2007

Water is the primary problem to solve if we’re to raise plants. I suspect this has always been the case almost everywhere (and offhand I can’t think of what the theoretical exception would be) and likely will be, at least until some theoretical descendants are working hydroponic plantations outside the orbit of, say, Mars, where the problem will be sunlight. Probably there’s some smiling herb grower now who’s working on an electricity-sparing solution to that.  

The conundrum, once we get that water, is balance. Surprise: the problem of water is also the problem of air.  

Winter’s coming in, and with luck we’ll have more rain. Some plants that have stoutly withstood the usual summer drought will succumb to a surfeit: succulents like cacti and some California natives like flannelbush are susceptible to crown rots and plain old drowning if they spend the winter in poorly drained soils.  

Roots, even those of big trees, lie mostly in the top two or three feet of soil. The more water-retaining the soil is, the more shallow most roots will be. They need some free oxygen, some air, around them, and soil with its pores and little spaces filled with water doesn’t have room for air.  

Containers also tend to drain slowly, often because something’s obstructing the hole in the bottom. (You wouldn’t be cruel enough to put a helpless plant in a watertight pot, would you? Aside from water plants and swamp plants that like wet feet, of course.)  

A paradox: a plant wilts when it’s too wet as well as when it’s too dry. The latter makes sense: water, moving through a plant’s circulatory system and out to its leaf tips and edges one molecule at a time, is part of what makes leaves and nonwoody stems stand up.  

So when leaves and stems droop, naturally we think of watering the plant. If we know the plant well enough, we can spot thirst before that, as leaves lost their usual luster and get just a little flaccid, a little tired-looking.  

Before rushing for the hose or the watering can, though, be bold and stick a finger into the soil at least one knuckle deep. A wilting plant in damp soil might either be temporarily coping with hot direct sun, or a fungal infection might be clogging its circulatory system. Fungi are present in most soils most of the time but, rather like the mildew on the bathroom wall, they get a boost from wet conditions.  

So cop a feel of your plants’ leaves and its soil, sure. But even before that, know what your plant will tolerate.  

The best way to figure that out is to know where the plant’s roots are. No, I mean figuratively. A plant of local ancestry will likely be OK in local soils. A plant from a mountaintop will want fast drainage. A plant from a riverside might not mind wet feet.  

The key to all that is the plant’s specific epithet—its Latin-sounding name. Uh-oh. But it’s not that hard, really. If you can order from a Thai or Italian menu, you can learn enough Latin to call your plants by name. 

Stay tuned.