Success with Pots and Planters

Self-watering planters, with their built-in water reservoirs, ensure that your containers can take hot, sunny locations.

Growing plants in containers is all the rage these days. Urban gardeners, and people with limited time or energy, may garden exclusively in containers. But most gardeners—even those of us with large traditional gardens—have at least some plants in containers. Windowboxes, deck and patio planters open up all sorts of creative possibilities, inviting us to experiment with new kinds of plants and plant combinations.

These days, there are thousands of interesting planters to choose from, in styles ranging from classical to modern, and in materials such as ceramic and terra cotta, as well as plastic, hypertufa, concrete, glass, wood and metal. Selecting a container is the easy part, compared to the challenge of deciding what to plant. I love composing new looks each spring with interesting foliage, unusual blooms and arresting color combinations.

But there's a dirty little secret about container gardening. It's not as easy as it appears. When newly planted, containers almost always look terrific. But once July rolls around, most planters start to look a bit tired, and by August, they're looking positively ragged. Petunias have stopped blooming, the lobelia has disappeared, coleus are leggy and wilt a few hours after they're watered. So what's the secret behind those glamorous planters you see in books and magazines?

There's really no surprise. It's all about the right soil, water and nutrients. These three factors are just more critical when a plant is trying to survive—much less thrive—in a few cups of soil. Container-grown plants require you to be just a little bit smarter and more attentive than you need to be out in your garden. Here are a few tricks I've learned along the way that have helped me keep my potted plants happy and looking great with a minimum of effort.

Especially made for pots and planters, Container Mix retains moisture yet drains well.

When it comes to soil, especially in a container, your goal is to provide plant roots with a growing environment that's loose and well aerated. Container gardens are usually much more densely planted than a regular garden, so plants are already competing for space. It's important that air, water and nutrients can move through the entire soil area. (Remember, there are probably no earthworms helping to keep the soil loose.) I'm convinced that soil is the most important factor for container gardening success. First of all, don't fill up your pots with garden soil—even if it's rich and loamy. I guarantee that in a couple weeks it will be rock hard and your plants will suffer. You don't want to use peat moss, either. It's too acidic and doesn't absorb water well. Coarse, soilless growing mixes, such as our Container Mix, are best. They contain a blend of sphagnum peat, perlite and vermiculite. For self-watering containers, try Self-Watering Container Mix, which is formulated for planters that wick moisture from a built-in reservoir. I always add in about 25 percent compost or good garden soil to provide the beneficial enzymes and soil organisms that help keep plants healthy. If I'm not using a self-watering pot, I'll often mix in some water-retaining crystals, too. These crystals absorb many times their weight in water and hold it until needed, releasing it slowly until you water again.

Though it's tempting to re-use soil from one year to the next, don't recommend it. The soil will certainly have become compacted, which means poor aeration and poor water retention. It may also contain a build-up of fertilizer salts or be contaminated with diseases and pests.

Your container-grown plants need to be fertilized frequently—at least every other week. Soilless mixes don't contain any nutrients, so adding compost and a granular organic fertilizer at planting time provides a good baseline. But daily watering quickly leaches nutrients out of the soil, and by mid-season, your plants will be relying on you for their nutrients. A water-soluble fertilizer, such as Plant Health Care or Multi-Bloom will ensure they get what they need to thrive. These fertilizers are rich in organic ingredients, including enzymes and humic acids to help keep the soil loose and promote healthy roots.

Minimize Your Watering Chores

The last critical factor for container gardening success is water. With such a small amount of soil and so many thirsty plant roots, containers dry out very quickly—especially on hot, summer days.

One trick is to nestle your pots together so they can shade each other and provide some protection from drying winds. Providing afternoon shade is another way to keep plants from getting parched. Adding water-absorbing crystals to your potting mix (as mentioned above) can be helpful, too. You might also consider using water-holding Hydro Mats, which can be cut to fit inside the bottom of almost any pot.

The ultimate solution is a self-watering container. Once you've tried one, it's hard to use anything else. The reservoirs usually hold enough water for several days. Roots stay moist, but not so wet that they'll rot. You can even add water-soluble fertilizer right into the reservoir.

With the right soil, consistent moisture, and adequate nutrients, you'll be able to enjoy picture-perfect pots and planters all summer long.

Kathy LaLiberte has worked for Gardener's Supply since it began more than 25 years ago. She lives and gardens in Richmond, Vt. Click here to read more of her Innovative Gardener essays.