There are plenty of good reasons to develop a skill set for growing food in small spaces. Maybe you only have a tiny balcony with sun for half the day? Or a hot, paved driveway but no other yard? Perhaps you're in student housing? Or maybe it's more of a time constraint: You'd like to have an expansive garden but you really only want to work on it for an hour a week. Or perhaps you just don't really eat that many vegetables and you'd rather just keep it small and simple.
Thoughtful, specific design is the primary way to get the most yield from the least square feet. Once you understand the principles of building living layers in time, space and function, you will be able to pull more out of gardens of all sizes. When it comes to designing small and/or container gardens, the three most important strategies are using microclimates, creating vertical space and avoiding waste.
1. Make use of microclimates. A microclimate is a spot that is hotter, wetter, cooler, sunnier, drier, shadier, more sheltered from the wind or a combination of any of these. This information is crucial to the design. For example, when you have determined where the hot spot is in your space, you will know where to plant the tomatoes and other summer vegetables like squash, beans, peppers and basil. Into the shady, cooler spots will go the peas and salad greens. Spots with mottled sun? That's where I'd put the kale.
Learn the microclimates of your site. Don't assume that a sunny patio is sunny in every spot, or that it's all the same temperature. The shady backside of a large south-facing rock will be a different microclimate than the space on the other side of the rock, and plants of different needs will thrive in each spot. Or not. You can also change microclimates by painting things white (to reflect the heat), or by placing rocks, bowls of water and other sun-absorbing items next to plants. You can make shade or build a wind break. Use your imagination to create new opportunities.
2. Maximize margins and vertical space. Google "vertical gardens" for a fun-filled evening of geeked-out garden inspiration. Build shelves, boxes, hangers, free-standing salad walls. Make note of microclimates up high, in corners, hanging from trees. Make vertical plans. Make plans in every direction. That tiny ledge you didn't notice before might be the perfect spot for a pot of oregano.
Think of the garden in 10 layers: roots, ground-covers, annuals, biennials, canes, vines, herbs, shrubs, small trees and tall trees. You don't have to use every layer but it helps to consider them all. Remember air circulation is just as important as soil and water, so don't congest the vertical space, just use it the same way you would a horizontal garden, leaving plenty of elbow room for plants to mature.
3. Avoid Waste. If you already have a garden and are revamping it to make it more efficient, clean out as much as you can so that you can come close to creating a blank slate. Be experimental but don't waste space or time. Make realistic attempts to raise food that already grows in the area. Keep the garden weeded, swept and free of clutter that infringes on the growing area.
In an urban area or a college housing situation, you might discover that gardening in built boxes and found containers is the best approach. You can grow food in just about any kind of container, as long as it has drainage and isn't made of something toxic that could leach into your food. I do NOT recommend growing food in tires, railroad ties, painted lumber or treated wood for that last reason. I also do not recommend using terra-cotta pots unless you paint both the inside and the outside of the pot with a water-based latex. (Spray paint works great.) The clay pulls water away from the plants and, unless you live a super rainy place, you don't want your containers to dry out so quickly.
There are many pros to container gardening. They're temporary and easy to move, they can be done on any porch, patio, terrace, rooftop, houseboat, flatbed or driveway. If you include beneficial herbs and flowers in your containers, they will beautify your life year-round. I don't see any actual cons to container gardening but there are a few important things to consider:
1. Soil and Fertility. The more yield you pull out of a section of soil, the more often you need to replenish that soil with fresh nutrients. This is especially true in container gardens because they are isolated and don't have access to the subtle yet powerful and extensive microbial network in the ground. Top-dress containers twice a year with fresh, finished compost and/or composted horse manure, then mulch on top of that with a mulch appropriate to the crop. (See "Mulch Much?" Nov. 26, 2015.)
2. Watering. Container plants need excellent drainage or the soil will get anaerobic. Drill holes in the bottom of the container and spread a layer of gravel to help the water percolate. Then layer in your fertile soil, plants and mulch. Containers dry out quickly, as do hotter microclimates, so keep that in mind and water about twice as often as you would with plants in the ground. It might seem like you can get away with it, but container gardens that don't get enough water will not yield. Visit them daily with the hose and tune yourself into the needs of your little garden. And that's one of the great benefits of having small gardens: You have the time to really get to know each plant.
3. Weeds and Companion Plants. It makes sense to plant a few different things next to each other in a pot, to create growing guilds that complement each other. Try tomatoes, marigolds and carrots together. But keep in mind that too many plants in one pot will cause all of them to suffer. As a general rule, try to provide at least two gallons of soil for each guild of three to four plants, layered in space and time. Meanwhile, all containers should be weeded meticulously so the chosen crops don't have to compete for water and nutrients. We'll get more into guilds and companion planting next month.