Most of us don’t have enough space in our gardens to grow everything we’d like to try. Even in my rather large gardens, I often ask myself, where will I put it? Maximizing what space we have is important, but to do so effectively, we need a method. Intercropping can help.

What do we mean by intercropping?

Intercropping, sometimes called interplanting, is growing two (sometimes more) crops in the same space, at the same time, while still leaving enough room for each to reach maturity. It differs from succession planting, which normally involves replanting crops periodically to extend harvest windows, and from rotation, which simply means growing a different crop next year. With intercropping, we purposely allow two or more different plants to occupy or share the same garden space. 

Intercropping can be designed to take advantage of horizontal or vertical space opportunities, or time (via differences in maturity and plant growth). In addition to potential increases in yields, biodiversity, and resilience, intercropping adds visual depth and features to your garden. Horizontally or vertically interplanted spaces form a layered arrangement, providing contrast in foliage color, size, and texture, plant height, and possibly flowers as well.

In a natural environment, whether a forest, prairie, or wetland, we rarely find a single plant species occupying a site. In a forest, we might have stately pines towering over midcanopy hardwoods and a shrubby understory, and beneath that a carpet of wildflowers, small groundcover plants, and mosses. In a natural prairie, Silphium and Eutrochium maculatum (Joe Pye weed) might stand tall above a waving sea of grasses, with shorter forbs and wildflowers down below. Nature is an intercropping expert. 

Getting Started with Intercropping

To begin, we can envision the three dimensions we have to work with: the horizontal, the vertical, and time. Horizontal in this case means your spacing and layout of plants, like how much space is between your tomatoes. Vertical, of course, is the up-and-down dimension and includes elements of vertical gardening. 

Utilizing the space above our soil provides more opportunity for growing, just as a skyscraper provides more office space than a two-story building of the same footprint. Time, when related to intercropping, is a consideration of which plants will take up that vertical and horizontal space at what portion of the growing season. 

Intercropping using horizontal or vertical spacing

Efficiently using vertical space in the garden offers many opportunities for creativity and design, but in this article, we’re focusing on productivity and efficient use of sunlight. The morning glories growing up your southern garage wall aren’t using the space at the bottom. The leaves on the bottom half of your giant sunflowers aren’t doing much, and leave plenty of room for some cosmos in the midlevel and a few marigolds or snapdragons at the base. 

Horizontally, we might decide there is wasted space, or lost opportunity, between our hills of pumpkin or melon seeds early in the season, and fill it in to use the area. Onions hate weed competition, but while they are small, there is plenty of room for a few radishes between them. We’ll get a spicy addition to our recipes, and keep a few weeds in check.

Intercropping using maturity intervals

Planning for plants to share space by using time to deconflict their needs isn’t as hard as you might envision. Not only can we use maturity times, for example, planting quick-maturing beets between our sweet corn rows, or planting pumpkins in our lettuce bed, but we can also use the seasonal changes in our plants. 

Later in the growing season, many plants have begun to die back or senesce, even though they are still producing. As the lower foliage on tomatoes dies off or is trimmed, ample space becomes available for planting compact basil or starting a row of fall carrots. By predicting when a plant needs room and when it doesn’t, we can use our garden spaces more effectively. Keeping the space busy with the plants we do want creates a natural mulching effect, limiting the area for weeds to germinate and reducing our subsequent weeding efforts. 

Intercropping is Often About Sunlight

When selecting plants to share space, we need to consider their physical environment needs. The candidate crops need to have compatible moisture, nutrient, and fertility needs because they will share the same root zone and irrigation schedule. After those criteria are met, the consideration often comes down to sunlight. 

We can match sunlight needs by planting two or three sun-loving plants together, or we can use the shade cast by a taller plant to provide relief for a shade-tolerant crop, or one that needs less light. For example, lettuces, which will still do fine in partial sunshine (and even better with a bit of shade in hot climates), can be planted on the north side of a bean trellis. 

We can also consider the sun’s position in the sky, and the resulting angle at which sunlight strikes the ground or a vertical surface. In the northern hemisphere, the sun will not be directly overhead for most of the growing season, but farther south in the sky. In fact, for gardeners in the continental United States, we are north of the Tropic of Cancer, and the sun will never be directly overhead, even on the summer solstice, because of Earth's tilt. 

For intercropping, that means sunlight always arrives at an angle, not straight overhead. You can see this effect by looking at a tree's shadow at noon and noticing it falls on the north side of the tree. The sunlight arrives not from overhead, but at a slant. Depending on your latitude and the time of year, the sun may strike a vertical surface at fairly significant angles. In this case, a leaf at the top will not shade one halfway down. The sun’s angle essentially creates more space for leaves to use than if they were only spread horizontally on the ground.

We can use this phenomenon to our advantage, like planting peppers at the base of a pole bean trellis, to more fully utilize our growing space. It also means we can accidentally shade out nearby beds or rows by planting something tall on the southern side of our gardens. A triple row of ‘Bloody Butcher’ corn, which can reach ten feet tall, would shade out quite a bit of garden in late summer if planted on the south side of the plot. The sun’s angle is the reason we plant those tall crops on the north side of the garden.

Intercropping Examples in the Garden

Intercropping is fun, but does take some planning to ensure the plants are not overcompeting and therefore struggling to produce. 

You might call it deconflicting: analyzing and planning out an intercropping strategy to minimize competition. We look at the limiting resource, whether sunlight or space, and deconflict it with our plant choices. As above, we can deconflict with horizontal or vertical spacing, and by maturity and growth times.

• Plant loose-leaf lettuces between cabbage transplants in early spring. Cabbage will eventually spread out and take up a huge amount of space, but while it is small, there’s a lot of real estate left unused in the garden. Lettuce, as a short-maturity crop, will grow, mature, and be ready to harvest before the cabbages take over the site. 

• Build a bean tripod to add vertical interest to the garden and save space. Plant the beans around the tripod legs, leaving an open space underneath. Normally, the bean foliage on my tripods is quite thick at the top, but a bit less so halfway down, allowing partial sunshine to fall under in the area between the tripod legs. It’s a perfect spot for a few potatoes (if it’s sunny enough), or some collards. If your beans create a bit more shade (some varieties do), the microclimate they create means you can plant kale, spinach, lettuce, or even peas, and they’ll have a bit of shelter from the powerful summer sun.

• Add flowers to a veggie patch. For example, plant ‘Dreamland’ hybrid zinnias a few inches from the base of your tomatoes. As the tomatoes grow and you prune off the lower leaves, it creates an open spot just large enough for these compact 10-12 inch tall plants to flower. The blooms will attract pollinators to the area, where they’ll do needed service for the many plants in your garden and add a splash of color to the garden or the vase.

• Grow early crops of kale, chard, beets, greens, and peas in your tomato and squash beds. These cool-weather crops can be planted as soon as the soil is workable, usually four to six weeks earlier than we dare plant out tomatoes or start pumpkins and squash. The cool-weather crops will fade as the warm-weather plants begin to take up space. In early autumn, reverse the process, transplanting cool-weather crops into the gaps and holes under your tomatoes and peppers. Trim a leaf or two from the vining squashes to make a spot. The young cool-weather crops will get a bit of shelter from the last heat of summer, and they’ll be established already when the frost kills the tender summer plants.

Happy Gardener Tip: If you are growing cold-season crops under a warm-season plant, for example, getting spinach and chard started under the eggplants and tomatillos, when the time comes, cut the frost-killed plants at the base and leave the root systems. Don’t yank them out. Cutting the dead plants at the base avoids damaging the root systems of the new crop and leaves food and habitat for your soil microorganisms, since the root systems are basically composted in place. By spring, there will hardly be anything left but a small stump, if that.