Neil Sperry: Container gardening 101

Angelonia in pots for repetition
Angelonia in pots for repetition Neil Sperry

Need a quick spot of color for a weekend event? Want a way to have flowers when you also have rabbits? Do you live in a town home but still want to grow herbs? There is one answer for all: container gardening.

You can grow just about any plant in a container that would succeed in a North Texas garden — as long as you’re mindful of a few basic needs.

Growing plants in pots also gives you great portability and accommodates very quick change-outs should one plant start to fade as another heads into its prime. Plus, any plant grown and shown in a large patio pot is displayed on a pedestal, which easily makes it the star of its surroundings.

It starts with the pots

If you shop any full-service nursery today you’ll find a wide assortment of pots and pot sizes. For the purpose of this landscaping discussion, we’re going to confine ourselves to large, decorative pots fit for the entryway garden, patio or poolside.

Decorative glazed pots from Southeast Asia started arriving on the market 15 to 20 years ago, and the flow hasn’t stopped since. They’re available in sizes as big as refrigerators down to smaller tabletop versions, and come in all shapes, styles and colors.

Terra-cotta pots remain an all-time favorite. They’re rather neutral in their appearance and blend into the surroundings quite well. And since they’re also available in many sizes and styles, it’s easy to create natural groupings.

The choices go on and on. There are probably as many types of containers as there are gardeners to buy them. I’d recommend trying to choose styles that are compatible with your surroundings and blend well with one another.

Whatever the color or style, one requirement is a working drainage hole. Unless the pot will be used as a fountain, it needs one, and if you find one that doesn’t have one, ask your vendor to drill one for you.

Quite simply, it’s impossible to grow plants in pots that don’t drain.

Also, unless you’re trying to highlight a particular spot in your garden with one singular container, you’ll probably want to choose three or five similar pots to create a little cluster of plants and their pots. When you use pots in this way, they replace, to some degree, some of the shrubs you might otherwise include in your plantings. Choose several different sizes and perhaps a few different styles (square vs. round, fluted vs. smooth as examples). Put an evergreen herb like rosemary in one, and bright flowers in another.

Some people use a little different approach. With an intentional focus on repetition in their landscaping, they choose five or seven identical pots (odd numbers are more visually pleasing), and fill them with identical plants. That’s a good way to outline a walk toward the entryway or draw attention to a focal point like a fountain or statue.

Consider the soil

Growing plants in pots allows you to blend or buy the perfect potting soil mix for your plants. It needs to retain moisture and nutrients, but you don’t want it to drain slowly. The best potting soils are usually surprisingly lightweight.

Sadly, most of the commercial potting soils I find in the market are much heavier than I like to use. That weight translates to lower-quality sources of organic matter and maybe even native topsoils.

I’m known to be picky about the potting soils that I use, and I almost always mix up my own. The recipe will vary slightly, but none of them ever contain any native topsoil (too variable).

For most of the plants that I grow, my potting soil will be about 50 percent high quality sphagnum peat moss, 20 percent finely ground pine bark mulch, 20 percent horticultural perlite and 10 percent expanded shale (mainly for weight and ballast).

If I’m growing ferns, aglaonemas and other moisture-loving plants, I’ll increase the peat content to 60 percent and drop the perlite and shale to 15 and 5 percent, respectively. Conversely, if I’m growing aloes, haworthias, cacti and other succulents, I will increase the amount of expanded shale to 30 percent of the total. Fine aquarium gravel is also attractive.

A word about design

Jimmy Turner, formerly of the Dallas Arboretum and now the horticulturist at the Royal Botanic Gardens in Sydney, Australia, brought the terms “thrillers,” “spillers” and “fillers” to the forefront of conversations about container gardening. The “thrillers” are plants that stand tall in their pots. They are the upright lines of the arrangement you’ll be making. In other words, they would be the first plants to go into your arrangement.

“Fillers” are plants that occupy the voids. Baby’s breath plays that part in floral designs. For outdoor containers it could be any rounded and somewhat open flowering or foliage plant. Finally, “spillers” grow out and over the sides, generally hanging down over the edges of the pots. In most cases they are trailing plants.

Neil Sperry publishes “Gardens Magazine” and hosts “Texas Gardening” from 8 to 10 a.m. Sunday on WBAP/820 AM. Reach him during those hours at 800-288-9227. Online: