In the Garden Articles

Container Plantings

by Joan S. Bolton

Not all gardens have to grow in the ground. Containers are becoming more popular than ever.

But rather than the tiny red clay pots of yesteryear, today's containers are bigger, bolder and can cost as much as a piece of furniture.

They're also given more prominence, as they flank entries, line walkways, fill corners and serve as focal points in the garden.

They're a quick fix, providing an instant pop of color, texture or movement, depending on what you plant.

Whether it's to dress up a space for a party, squeeze more plants onto a patio or add another design element, gardening in containers provides infinite possibilities.

Getting Started

Choose your container first. Its overall look will determine which plants will look best. Plus, you'll know how much space you'll have to plant in.

From a trends point of view, small pots are out -- unless you cluster them or display them on a rack. When going solo, the bigger the better.

That's where materials and price come into play. In the larger sizes, lightweight plastic and resin pots are far less expensive than clay. They're also easier to move around. Yet they don't have the same solid feel as clay. And they don't come in nearly as many colors and styles.

Wood containers, such as redwood boxes and whiskey barrels, are an alternative. But the constant contact of moist soil to wood means they're likely to rot out after five to 10 years. Some high-end nurseries and catalogs offer modern containers constructed of metal. The thickness and type of metal will determine how long those boxes will last.

Next, consider the architectural style of your house. Pale pottery or white wood boxes, for example, go nicely with a traditional house trimmed in white. Sheet metal or copper might be more in tune with a contemporary home.

Also consider your garden style. Natural terra cotta pots look great in native, succulent or Mediterranean gardens. Rustic corrugated drain pipes or mosaic tiles embedded in clay better suit an eclectic or whimsical garden.

Selecting Plants

The path of least resistance is to buy a "color pot," which is a decent-sized plastic pot already plump and full with an assortment of blooming plants. Expect to spend $15 and up.

If you like the combination, that's great. But you might also be stuck with someone else's vision. The color pots that I've seen lately have been filled with so many different kinds of plants that they feel more like a jumble of leftovers than a pleasing design.

Instead, I like to treat my large containers like bouquets, choosing height for the center and spillers or trailers to soften the edges. The height might come from a tree rose, ornamental grass, New Zealand flax (Phormium) or an upright succulent. Depending on the plant, I might stop right there. In the sun, fountain grasses and some New Zealand flax, for instance, will fill a whole pot, then weep at the edges. In the shade, richmondensis begonias do the same.

Otherwise, I move on to such trailing plants as creeping thyme, blue lobelia, bacopa, verbena or whatever else seems apt at the moment. Right now, I'm trying out a yellow native beach primrose (Camissonia cheiranthifolia) with a white-blooming Moondance tree rose. The primrose is pretty straggly at the moment. But I've been promised that it will fill out with summer heat.

Another approach is to carpet a container with small, similar plants that might get lost in the garden at large. This could be an array of pansies in compatible colors or succulents with contrasting leaves.

Many annuals and succulents have shallow roots. So rather than a deep pot, you can go shallow and broad. Be sure to place these containers where you can admire the individual specimens up close.

If you do have some little red clay pots kicking around, plant a single ornamental in each and group them together. Or plant smaller herbs, such as basil, parsley and chives, and place them in a sunny spot.

On a much larger scale: if you have an area that you'd like to screen, look for a sturdy, wide trough that you can set a trellis in. Then plant a vine to work its way through the lattice. As the vine fills in, it may provide some wind resistance. So be sure the trough is heavy, broad and deep enough to not blow over. If you choose a lightweight resin container, line the bottom with rocks or bricks before filling in with potting soil.

Putting It All Together

Even more so than in the ground, perfect soil is key to growing plants successfully in containers.

Don't use dirt from your garden. It will be too heavy, too sandy, too dense or otherwise too incomplete. Instead, use lightweight, fast-draining potting soil. While you may choke at the cost, the bagged stuff is worth the investment.

Surprisingly, potting soil typically consists of no dirt. It's a fluffy blend of organic materials, such as sphagnum peat moss, composed forest products or composted manure, along with inert materials, such as vermiculite, perlite or sand. There may also be earthworm castings or a few nutrients to get your plants started. But unless the bag specifically notes fertilizer has been added, plan to mix in a handful of slow-release fertilizer granules or use a water-soluble product when you water.

All-purpose potting soils are fine unless you're planting succulents. If that's the case, look for a special mix of coarser, grittier materials.

Make sure there's a hole at the bottom of your container. Then line the bottom with porous weed cloth, pantyhose or a layer of gravel or broken pieces of a clay pot. This will prevent the potting soil from washing out the bottom when you water.

If you're planting an exceedingly tall pot -- say 3 feet or taller -- fill the next 6 to 12 inches with lightweight perlite or vermiculite to ease the overall weight.

But for most pots, start by filling with potting soil up to the depth of the base of the largest plant that you'll be planting.

For instance, if your centerpiece is a one-gallon delphinium, the delphinium is sitting in about 6 inches of soil. Your finished soil line should be about 2 inches shy of the top of the container. So fill the container to 8 inches from the top.

Firm the potting soil a little -- don't squash it -- to compensate for settling. Then remove the delphinium from its nursery pot and set it on top of the potting soil. Fill with a few inches of potting soil to hold the delphinium securely. Fit in your spilling plants -- which may be from 4" pots or pony packs and therefore have a shorter planting depth. Then fill in and top off the remaining spaces to your desired finished height.

Note that because you're providing such perfect soil, you can plant your container plants closer together than what the tags recommend. Those recommendations are intended for planting in the ground.

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Watering Your Pots

Plants grown in containers need more frequent watering than those in the ground. They dry out faster for a number of reasons:

Potting soil is designed to provide good drainage.

Plants are often placed closer together, which means their roots draw more moisture out of a limited space.

In the ground, only the soil on top is exposed to swings in temperature that can speed evaporation. In a container, the sides are vulnerable to the elements, too.

On hot or windy days, your containers may need watering daily. If you put larger pots on an existing drip irrigation system, you may still need to supplement with hand watering.

Fertilize more often as well. Your more frequent watering will leach out nutrients more quickly.

Seeds of Wisdom

On a wood deck or flagstone or concrete patio, set out several bricks, pieces of flagstone or similar-size cobbles to lift your containers by a few inches. This will help to prevent your containers from making marks on the surface.