| By Patty Glen Leander
Contributing Writer |
Interplanting may sound like a complicated agricultural term, especially to novice gardeners who are new to horticultural lingo, but if you’ve ever grown basil between your tomatoes or planted flowers at the edge of the vegetable garden, you have successfully interplanted! The technique of interplanting — growing smaller, fast-maturing plants among larger, slow-growing ones — is nothing new; it has been practiced by ancient cultures around the world and today it is especially popular among organic farmers as they move away from monoculture systems. The primary objective of interplanting is to optimize space and maximize yield, but interplanting also encourages beneficial insects, deters or confuses detrimental pests, increases biological diversity, protects the soil, discourages weeds and adds interest and beauty to a garden. We’ll look at three techniques to successfully incorporate complementary plant combinations into your garden: fast and slow, tall and low, friend and foe.
FAST AND SLOW
Slow-growing vegetables, especially when properly spaced with their mature size in mind, take up a significant amount of garden space during the growing season. Think about tomatoes spaced two or three feet apart or a row of onions in place from January to June. Interplanting quick-growing vegetables among slow growers allows you to take advantage of the yet untapped resources of soil, water, nutrients and sunlight to reap a small harvest before larger plants take over.
A common example involves growing fast-maturing radishes among slower growing carrots. In this instance, radish and carrot seed can be mixed together and planted in the same row or the radish seed can be planted a few inches away on either side of the carrot row; either way, as the radishes reach maturity they are harvested, leaving room for the carrots to mature. Lettuce, radish or spinach could be interplanted between transplants of broccoli, cabbage or cauliflower. Onions and garlic could easily share space with spinach, beets or lettuce, all shallow-rooted, cold-tolerant vegetables that can be harvested before the onions and garlic begin to enlarge.
With a little forethought, interplanting can be especially useful to merge the seasons in Texas, where our late-winter plantings are usually taking up space when the time for spring planting rolls around. Instead of planting a full row or an entire bed with cool-season crops, space the plants with interplanting in mind. If you are planning to grow tomatoes in the spring, for example, place stakes or tomato cages every three feet where the tomatoes will go, then at the appropriate time for your region plant quick-maturing crops like arugula, turnips, lettuce, beets, radish or Asian greens in the area in between. You will have the space reserved for tomatoes, and the surrounding crops will gradually be harvested as days get warmer and the tomato plants grow bigger.
Some gardeners prefer to utilize the space between tomatoes to grow basil or Swiss chard; as the sun gets hotter the chard and basil will benefit from the shade provided as the tomatoes grow larger. Or make a small but intensive planting of fast-growing bush beans between tomatoes, pull them up when they are finished producing and let the tomatoes take over. Such closely spaced plants may not reach their full potential in yield, but if that’s all the space you have, a few beans are better than none.
Another approach is to leave extra space (at least three feet) between your early-spring transplants of broccoli, cauliflower or cabbage. Cover the unplanted area with mulch. Then, after the threat of frost has passed, simply pull the mulch away and plant seeds of squash, bush beans or okra. The brassicas will be harvested soon after and the squash, okra or beans will have a head start on their growth rather than waiting on you to harvest the broccoli while you scratch your head wondering where in the world you are going to make room for all your seeds at the start of the spring-planting frenzy.
TALL AND LOW
Whether you live in a newer home with a smaller yard or an older home with tall pines and spreading oaks, sunny, garden-friendly real estate is harder to come by these days. Take advantage of the sun you do have and increase the productivity of your garden by allowing vining plants to occupy the vertical space above the ground while low-growing plants reside below. Sprawling, spreading and vining plants (such as cucumbers, peas, pole beans and small-fruited winter squash or melons) can be trained to grow on a trellis, fence, arbor or even a sturdy tomato cage. In the fall beets, radishes, lettuce or carrots can be planted at the base of vining sugar snap peas; in spring a row of low-growing bush beans can be planted at the edge of trellised cucumbers. Flowers also make suitable companions for vertical vegetables: sugar snap peas with pansies or alyssum, cucumbers with marigolds or zinnias, even a few morning glories or moonflowers sharing a fence with climbing beans.
On the flip side, the shade created by vertical vegetables can be used to an advantage, especially when setting out transplants during the transition from summer to fall. And although all vegetables produce better in full sun, keep in mind that root crops and leaf crops will tolerate some shade.
FRIEND AND FOE
Another consideration when interplanting is to think about how plants complement each other when grown together. Rather than focus on conventional companion planting suggestions which are based primarily on anecdotal evidence and peppered with inconsistent results, let’s focus on more tangible benefits of plant groupings. Research has shown that biological diversity, both in the soil and among plants, improves plant health and increases productivity. Rows or garden beds with mass plantings of the same vegetable look especially appetizing from a pest’s perspective and also facilitate the spread of disease. But break up a solid planting of a particular vegetable with an alternative disease-resistant variety, a different plant species or pungent foliage and you’ve made life a little more difficult for hungry pests and pathogens as they attempt to travel from plant to plant.
Colorful flowers in and around the garden attract pollinators and help create desirable habitats for other beneficial insects. Aromatic herbs or pungent alliums mask the smell that can draw a pest to the garden, and when allowed to bloom they provide pollen and nectar. Bees love borage, mint, sage and basil. Dill and fennel attract and support all stages of ladybugs. Radishes are so attractive to flea beetles that they can serve as a trap crop, luring beetles away from more valuable vegetables. These plant groupings not only add beauty, but they also produce a natural synergy in the garden. And with so much life and energy working on your behalf, you’ll want to do your part and minimize or eliminate toxic pesticides.
Knowledge of a plant’s growth habit both above and below the ground will help you discover compatible combinations. Deep-rooted plants like tomatoes, watermelons, winter squash and okra are best planted with shallow-rooted vegetables to reduce competition for nutrients, moisture and living space underground. The “Three Sisters” combination, a Native American custom of grouping three main food crops — beans, corn and winter squash — is a time-honored design that combines the harmonious and biodiverse principles of intercropping. The corn is planted first, often in hills, or groups, of 4–6 seeds. Pole beans are planted a few weeks after the corn germinates and squash is planted among the hills. As the beans grow, the corn supports their upright habit and in return the beans help anchor the shallow-rooted cornstalks while enriching the soil with nitrogen.
As the deep-rooted squash spreads out, its broad leaves cover the ground, serving as a living mulch to protect the soil and shade out weeds, eventually producing a storage crop for winter. Varietal selection is important when growing a Three-Sisters garden; as you can imagine, Native Americans did not use fragile ‘Supersweet’ corn or improved varieties of tender, stringless pole beans. Instead, they used the hardiest beans and native corn that would be used for drying, winter storage and the next year’s seed. If you wish to experiment with a Three-Sisters garden, try old-fashioned, sturdy varieties of pole beans, corn and heirloom squash. Suitable varieties might include ‘Stowell’s Evergreen’ or ‘Country Gentleman’ corn, ‘Rattlesnake’ or ‘Genuine Cornfield’ pole beans and any variety of cushaw squash.
When it comes to interplanting there are no hard and fast rules. The plants you choose to grow as well as your limits of time and space will determine what your intercropped garden will look like. So mix it up, experiment and discover what works for your garden space and your style. As long as you plant vegetables in the proper season, group them to complement their growing requirements and add to the biodiversity of your piece of earth, your garden will be a haven for plants, a beacon for beneficial insects and a playground for your senses. Not to mention a feast for your appetite.
SEASONAL COMBINATIONS
The accompanying chart will help with seasonal combinations:
COLD SEASON
Fast-Growing: Arugula, Asian greens, beets, lettuce, mustard, radish, spinach, Swiss chard, turnips.
Slow-Growing: Broccoli, Brussels sprouts, cabbage, carrots, cauliflower, garlic, onions, peas.
WARM SEASON
Fast-Growing: Bush beans, cucumbers, okra, summer squash.
Slow-Growing: Corn, eggplant, melons, peppers, potatoes, pumpkin, winter squash, tomatoes.
