7 Tips for Container Gardening

Even if you don’t have a yard or access to a community-garden plot, you can still harvest a bounty of produce all your own. Planting a container garden is a great option for people who have temporary or limited space. These seven tips will help you get a container garden started with success.

1. Use a big container.

Don’t be tempted by small, cute containers. Small containers are mostly for ornamental purposes; plants need plenty of deep root space to grow properly. If the container is too small, plants will be stunted, unproductive and unhealthy. I look for containers that are at least 10 inches wide and 10 inches deep. Larger plants, such as tomatoes, squash, sunflowers and root vegetables, need containers with a much larger soil capacity, preferably at least 5 gallons. (Think of a 5-gallon paint bucket.) You can get away with smaller containers for lettuce and other salad greens, provided the plants are harvested at an earlier stage.

2. Provide good drainage for your container plants.

Plants need oxygen for respiration in their root systems. Many containers, even those sold at good nurseries and home centers, do not have holes in the bottom, so they slowly fill up with water. Nearly all plants will suffocate or die of root rot if the containers fill up with water. If using wooden boxes, plastic pots or metal drums, drill some drainage holes in the base. To prevent soil loss, cover the holes with a piece of landscape fabric or screen mesh before filling the container with soil. A layer of gravel is not needed because it can cause more serious drainage problems if it clogs up with soil.

3. Keep your plants well-watered.

Some kinds of planters, particularly those made of terra cotta, wood or cloth, can let a lot of air in the sides. This airflow dries out the soil more quickly, requiring more frequent watering. Also keep an eye on any plants that are placed on patios, walkways or other surfaces, because these can heat up quickly on sunny days. If you have space at the top of a container, add a layer of mulch, such as compost, shredded paper, straw or coconut fiber. This will seal in some moisture and prevent rapid evaporation, extending the time between needed waterings. Alternatively, consider using a self-watering container, which includes a water reservoir at the bottom; these are available in most garden centers and from many online retailers if you choose not to make one yourself.

4. Choose a light, airy soil mix.

Find a potting mix that contains plenty of organic matter, such as bark fines, peat, coconut coir or compost. One of these should be the first ingredient listed in the mix. The potting mix does not need to contain any soil, even though that word may be used. Organic material will absorb more water than your native ground soil and will provide plant roots with the structure and aeration they need. Potting mixes that contain perlite, vermiculite or pumice also ensure proper aeration. If you wish to make your own mix or amend your native soil, these amendments are available in small bags at nurseries.

5. Fertilize plants regularly.

Unlike their ground-based counterparts, plants in containers depend on you for 100 percent of their nutritional needs. Use a balanced organic fertilizer that contains both macronutrients (nitrogen, phosphorus, potash) and micronutrients (including calcium, magnesium, sulfur and trace minerals). If you are growing small trees or bushes in containers, look for a specialty fertilizer appropriate for that type of plant (e.g. citrus). Scratch the fertilizer into the top few inches of the soil around the plants, avoiding direct contact with the roots or stems.

6. Refresh your soil every year.

Each spring before planting, remove the top few inches of soil from the container, add some new soil mix, and fertilize again. This will keep the soil renewed and fertile. Permanent container plants, such as small trees and bushes, need to be removed every few years and root pruned to prevent them from strangling themselves. If possible, do this while the plant is dormant. Use a sharp utility knife to cut off a few inches of root material from each side of the plant. Then add some new potting mix, return the plant to the container, and water it well. Regular root pruning will prevent plants from becoming root bound.

7. Get some wheels.

Containers full of wet soil can be very heavy, yet you may need to move your plants to overwinter them or take advantage of shifting sunlight patterns during the year. Planter stands with wheels are available at many nurseries, and they will prevent you from breaking your back when moving time comes.

About the Author: R.J. Ruppenthal is author of the book Fresh Food From Small Spaces: The Square-Inch Gardener’s Guide to Year-Round Growing, Fermenting, and Sprouting (Chelsea Green Publishing, 2008). He is a licensed attorney and professor at Evergreen Valley College in northern California.