I used to live in a townhouse and had no garden space that wasn’t covered over, so I tried growing some plants in pots.
That . . . didn’t work very well. Everything had to be heavily watered once a day, preferably twice, and that just wasn’t sustainable. So everything died.
I’ve been experimenting with pots again since moving to this house, and I’ve discovered a few things. Maybe these will help anyone who wants to grow a garden in pots in a place where the humidity is nonexistent and the summer heat is high.
Discovery #1: Pot color.
Black pots will cook your plants if the sun goes above 90 degrees F and the pots are in full sun. Roots don’t generally want to be 100+ degrees F. If all you have are black pots, you can alleviate this issue by burying the pots at least halfway down into the ground, or by painting the pots white, or by surrounding them with something white (a white cardboard box, maybe). If you can make (or buy) light-colored pots, try those.
Discovery #2: Pot materials.
Do nooooooooot use clay pots. Or fabric grow bags. Or cardboard. (Which can make quite nice pots in wet climates. Please note that it needs to be brown cardboard only with all tape, labels, and glossy sides removed.) Those dry out significantly faster than plastic. If you’re in a very wet climate, that’s a good thing. If you’re in an arid climate, the plants will probably die. If you don’t want to use plastic, try something that doesn’t let moisture escape from the sides easily, like glass, glazed ceramic, wood, or metal.
Discovery #3: Consider the season.
In my climate – zone 7b with averagely wet winters – pots are great in the winter, so they’re a convenient way to stratify seeds. Conceivably a winter garden could also be grown in them, as long as you remember that the roots will get colder at night than if they were in the ground. In winter here, pots can be left in full sun and mostly ignored.
Discovery #4: Make the drainage holes smaller.
Most purchased pots, including the ones that come with plants from a nursery, have very large drainage holes. In an arid climate, you don’t want that! You want to have a teensy weensy amount of drainage, no more than absolutely necessary to let excess water leach out the bottom to prevent root rot. You can decrease the amount of drainage either by blocking some of the holes that are there, or by making your own pots and only making teensy scissor nicks or needle pinpricks on the bottom.
Discovery #5: Turn the lower half into a sponge.
Make the bottom half of the pot very good at absorbing water and very reluctant to let it drain out. I generally do this by sticking several layers of cardboard on the bottom, filling the rest of the bottom half of the pot with wood chips, and filling the top half with native soil. You don’t need to purchase potting soil, and in fact, you don’t want to. It’s much too well-draining. And it’s not particularly eco friendly.
Discovery #6: Stick kitchen scraps in the bottom, too.
Especially if you’re filling the bottom with carboard, paper, autumn leaves, wood chips, etc., it’s going to be full of carbonaceous materials. Stick some nitrogen in there to keep the carbon company and turn it into rich, fluffy compost. Kitchen scraps are great. (Be aware that if you add anything with seeds, you will probably get volunteers.) Diaper fluff from the interior of wet diapers is even better, because it also adds free water crystals and paper pulp that will compost rapidly. If you do this, not only will the plants need less water, they’ll also need no fertilizer.
Discovery #7: Mulch.
You definitely need to have half an inch to an inch of mulch on top of the soil in the pot. Small wood chips work. So do leaves or grass clippings or shreds of paper or cardboard. Just don’t stick weed seeds in there accidentally, if you can help it.
Discovery #8: Capture the drainage water.
Either have some kind of tight-fitting saucer underneath to capture the drainage water and wick it back up to the pot later, or put the pot next to a plant in the ground that you wouldn’t mind watering. A fruit tree, for example. Don’t use a tray underneath with a lot of surface area exposed to the sun. If you do, all drained water will evaporate.
Discovery #9: Use very large pots.
The bigger, the better. A quart is not big enough. A gallon is not big enough. A ten gallon pot may be big enough. A twenty gallon pot or bigger is probably safer. Remember: the larger the pot, the smaller the surface area exposed to the sun, thus the less water will evaporate from it per hour. So the bigger the pot, the better.
Discovery #10: The pots still can’t be in full sun.
They just can’t. Not in zero humidity and summer heat above 90 degrees. Well, they can, if you really want to water them every single day, but do you really want to see everything die if you forget to water it one time? Give them no more than four hours of full sun per day. If you live in an area with very intense sunlight, like I do, that will be enough for most “full sun” crops to thrive.
After a lot of trial and error, I’m doing all of those things with some plants right now, which means I can usually get away with watering them only once a week.
