The author, John Marek, is a writer and executive director of the Anson Economic Development Partnership.
Author’s note: For the next seven weeks, Field Notes will focus on sustainable living, community agriculture and food security. These “Summer of Sustainability” columns will feature practical advice on growing, harvesting and preserving your own foods, as well as more philosophical essays on life and the way we live in the modern world.
Whether it is possible to grow meaningful quantities of vegetables on a typical patio or balcony is generally predicated on your definition of “meaningful.” If you are looking to supplement your diet significantly, the answer is, unfortunately, no. But if your goal is to experience the satisfaction of putting something on your plate that you raised from a seed, then absolutely yes.
Apartment and condo dwellers can grow tomatoes, beans, peas, cucumbers, squash, herbs and even corn in a surprisingly small space. And because the compact varieties of these plants are smaller than their full-size garden counterparts, they mature faster and can still be planted for a harvest later this summer.
Getting started with container vegetable gardening can be as simple as heading to your local hardware store or garden center, buying a large pot, potting soil and a Patio tomato seedling. The dozen golf ball-sized fruits you will get from doing that may not augment your grocery list
much but will undoubtedly give you a sense of satisfaction and accomplishment that will leave you wanting more.
A more productive container vegetable garden requires a little more planning. It is also essential to understand that gardening at this level is probably not a cost-saving measure. You will almost certainly spend more on the materials than the value of the vegetables you harvest. The good news is the pots, tools and, to some extent, soil can be reused year after year, so over three or four years you might be able to break even.
The first step in creating a container garden for your patio, balcony or deck is determining the layout and type of containers. Most vegetables require a minimum of six hours of sun each day, but eight is better. Observe the area where you plan to place your containers over two or three days and see when and where the sun hits it. Remember that the sun’s angle changes with the seasons, so it is best to make this observation as close to the growing season as possible. It would help if you also considered the placement of furniture, grills, toys, etc. The sunniest part of your patio may be the center, but few people are willing to give that prime space over to a collection of pots. You can then make a simple drawing to help illustrate where the sun falls and for how long, and the placement of furniture and accessories. Vegetables that produce large fruits, like tomatoes and peppers, should get the sunniest spots, while green, leafy vegetables like lettuce and kale can get by with slightly more shade.
One of the most important decisions you will need to make for your container garden is the containers. There are two basic directions you can go; raised beds or pots. This is primarily a question of aesthetics. Some folks are comfortable having a large wooden or metal trough on their patio; others are not. From a horticultural standpoint, the raised bed is the more desirable option as it is easier to maintain a consistent moisture level across the larger soil volume. However, 16- to 20-inch pots are also practical. I would not go smaller than 16 inches, with the exception of certain herbs, like dill and basil, which can be successfully grown in pots as small as six inches.
The material of the raised bed or pots is also a consideration. Raised beds are typically wood, plastic or metal, and any of those materials work fine for gardening. For wood beds, cedar is often used because it is naturally rot-resistant. Even so, a plastic or metal bed will last longer.
While you can build a bed directly on your patio or deck, most people opt for one with legs. These have the advantages of (somewhat) keeping unwanted critters out of your plantings and requiring less kneeling and bending. The soil in the bed needs to be six inches deep. Many commercially-available raised beds are deeper, and that’s fine, but you only need six inches.
Pots come in thousands of different designs but are generally made from clay, plastic, metal or glazed ceramic. Each material has advantages and disadvantages. Clay is porous, which allows the soil to breathe but also allows moisture to escape. Metal conducts heat into the soil, which can be an advantage early in the season, but dramatically increases evaporation during hotter weather. Plastic and glazed ceramic are non-porous and less heat-conductive, but many gardeners do not like the look and feel of the plastic or have concerns about chemicals leaching from it. Glazed ceramic is, by far, the most expensive option.
Soil mixes specifically blended for raised bed and container gardening are commercially available, and they will work, but you can create a soil mix at home that is better and costs about the same. The formulation is called Mel’s Mix. It is named after Mel Bartholomew, the inventor of the Square Foot Gardening technique. While an in-depth discussion of this technique is beyond the scope of this article, I encourage you to check out the Square Foot Gardening website for more information. Mel’s Mix consists of equal parts compost, peat moss and coarse vermiculite. I have worked with dozens of different soil formulations in my gardens, and nothing else comes close to Mel’s Mix for moisture management. The key is the vermiculite, which absorbs excess moisture from the other two components and then releases it back as they dry out. With Mel’s Mix, it is virtually impossible to overwater, and the interval between required waterings will be 10 percent to 20 percent longer than with commercial raised bed soil.
There is a diversity of opinions regarding filling the raised bed or pot with soil. I have seen articles that suggest putting two inches of gravel, a sponge, styrofoam packing “peanuts” or sand in the bottom of containers as moisture management and to decrease the volume of soil required. I use gravel or sand, but I suppose those other materials work, as well. Again, for raised beds with Mel’s Mix, you only need six inches of soil, so if your bed is significantly deeper than that, you will almost certainly want to add a substrate layer. On the other hand, pots do not follow the six-inch rule because the overall soil volume isn’t sufficient to maintain a consistent moisture level, so you will want to have a full nine or 10 inches of soil above any substrate material.
As container vegetable gardening has grown in popularity over the past decade, seed companies have developed compact varieties of many garden favorites. These plants are bred specifically to grow to maturity in a smaller area, sometimes as little as one-third of the space required by garden varieties. Examples are Spacemaster cucumber, Blue Lake 47 green beans, Fordhook zucchini, Patio tomato and On Deck corn. Yes, you can grow corn in a pot on your deck! The vegetables these plants produce are sometimes slightly smaller than garden varieties, and they generally do not yield as much; that is the trade-off.
Plant the seeds according to the instructions on the package. Use the diameter of the pot as a general guide, so if you are planting beans in a 16-inch pot and the instructions call for spacing the beans three inches apart, you will plant 10-12 seeds. Larger plants like tomatoes and zucchini should be one to a pot.
Moisture management is an important consideration, especially on a concrete patio in full sun. Containers should be checked regularly, once a day during the hottest part of the summer, and again, it is very difficult to overwater Mel’s Mix, so erring on the side of moist is the way to go.
Soil mix made with quality compost contains all the nutrients most vegetable plants need, but some container gardeners like to add fertilizer. While a little Miracle Grow won’t hurt anything, I prefer just to top-dress nutrient hogs like tomatoes and peppers with an inch of compost midway through the growing season.
At the end of the season, which in these parts may last into November, you can bring the pots in or cover them with a layer of finely shredded leaf matter for the winter. In the spring, mix that leaf matter and a couple of trowels full of compost back into the soil, and you are ready to plant again.