A garden I admire a lot has no lawn, no trees. It's the sort of garden you might see in front of a whitewashed house in Greece or Sicily. Flowers spill out of a dozen of more containers—clay pots of different shapes, a couple of olive oil cans, a blue plastic bucket, a chipped ceramic bowl. The flower colors are mainly pink and red. There are bougainvillea, plenty of geraniums, maybe some basil, and a pot of coleus in the shade by the door.
The Mediterranean sun, of course, brings out the flowers. And the plants manage to thrive in the heat because they're watered regularly, probably by a woman dressed in black. The effect is both generous and thrifty; the flowers abundant, the containers humble.
Many Slate readers, to judge from the e-mails you've been sending, have only a balcony or a small patio. Rest assured: You can be a true gardener with a half-dozen or dozen containers, or just two pots on your front steps. Container gardening can be a great relief from having to deal with actual dirt and the rocks and weeds that come with it.
A cautionary note, though. A plant in a pot is a lot more dependent on you than it would be if it were in the ground and could spread out to look for water and nutrients. Think of it as a pet—a quiet and thirsty one. How often should you give it water? You need to check every day, no kidding. Pots in the sun need water almost daily. Small pots dry out faster than large ones. Woodland plants, like ferns and impatiens, want to stay moist.
The aspiring container gardener may find him- or herself stopped at the outset by a first piece of advice, which is crucial but seems bizarre and contradictory. Garden books, plant tags, and nursery staff all tell you to give your plants "moist, well drained soil." Or in fancier words, soil that is "fast draining yet water-retentive."
If your bathtub is well drained, all the water goes down the drain. After a minute or two your tub is not moist. Indeed, water retention would be a bad thing. For the soil in your pots, the water has to flow through, not puddle. That conscientious Greek or Sicilian woman dressed in black (or her plant-appreciating male equivalent) has drilled holes in the bottom of her turquoise bucket, her olive oil cans, her ceramic bowl, and every one of her clay pots.
Here's the reason. Roots need air as much as they need water. If the soil is saturated, all the tiny air spaces become waterlogged and sludgelike. Unless you're growing a water-adapter like a lotus or a mangrove tree or rice on your balcony, the plants in your care will rot.
But the soil also has to be able to hold moisture without getting saturated. This can work if it has plenty of organic content—tiny bits of peat moss or decaying leaves or bark that act like sponges, holding the water where the roots can get at it. In addition to these water-holding elements, commercial potting mixtures generally have some mineral material—usually perlite or pumice—that keeps the soil fluffy and airy. The mixtures are soilless, so they're really potting stuff rather than potting soil.
You could easily end up paying as much for a bag or two of potting stuff as for your plants. But it's worth it. Digging up regular old soil from your garden is a mistake. Garden soil is too dense to use in a pot. Some books say garden soil comes bearing diseases or critters, but the main drawback is that it's heavy and airless.
Pros, not surprisingly, use Pro-Mix or Pro-Gro, which come in impressive bales. Dedicated gardeners can also make their own potting mix. To get maximum performance out of your plants in a limited time, you need to add some fertilizer to whatever potting stuff you buy. One easy method is to mix in a slow-release granular fertilizer (Osmocote is a common commercial product available in gardening stores) before planting. These little pills release their contents—nitrogen, phosphorus, and potassium—over four months. Conveniently enough, that takes you from May to August or June to September. If you're growing edibles, dissolve fish emulsion or liquid seaweed in water (you can get what you need at any garden center) and use the solution to water your plants every two weeks. Flowers and herbs that prefer lean pickings—like geraniums, lavender, and rosemary—won't benefit from more frequent injections. Another alternative: My container plants began to produce in almost frightening abundance after I gave them a cup or two apiece of earthworm castings (dried, not mushy), which I'd gotten from a mail-order firm with the perhaps overexcited name Gardens Alive!
The other key to success, as in any kind of gardening, is to put things in the sun that like sun and things in the shade that like shade. Here are a few plants I like for containers that have a good chance of staying alive—which is why I like them. Some names may be unfamiliar but thanks to the miracle of search engines you can easily get descriptions from the Web.
Phormium, also known as New Zealand flax
Calibrachoa also called Million Bells. This is an impressive ever-bloomer, like a small petunia.
Scaevola, blue with a white eye. Blooms almost as fiercely as calibrachoa.
Geraniums, especially the variegated ones
Gartenmeister Bondstedt fuchsia
Helichrysum petiolare, also called licorice plant
Don't buy plants that are too small. This is a common mistake, particularly in a region with a short growing season. And choose plants that are pleasant to have nearby: cherry tomatoes to pluck, leaves that send out a scent when you brush by them—basil, lemon verbena, scented geranium, mint.
It's no longer considered good practice when planting to put pieces of broken pot over the drainage hole at the bottom of the pot or bowl. Pros put a small square of landscape cloth at the bottom instead to keep soil from coming out. A paper towel or a piece of newspaper will work almost as well. Put soil (really potting stuff) into the pot until it's about four inches from the top. Place your plants (still in their little nursery containers), as you want them. When you take them out of their containers, set the largest plant first, add some soil, and then set the other plants, working from the center out. Leave about two inches of room from the top of the pot. Water thoroughly—but spray, don't drown.
Lately, combinations of different kinds of plants are all the rage—one tall, a couple of spreading, a few trailing. This can be gorgeous when it works, but it can also look excessively florist-y. There's a lot to be said for one geranium in one clay pot.