By planting marigolds, cosmos, and sunflowers in your vegetable garden, you might be practicing intercropping without knowing it. Intercropping is an age-old farming technique increasingly used by home gardeners. Like all gardening that yields an edible crop, it requires a bit of planning but is well worth the effort. Intercropping improves plant health, which means a more plentiful harvest.
Read on to learn about what intercropping entails, how you can apply it in your garden, and what distinguishes it from interplanting. a term that is often used interchangeably when there actually is a difference between the two.
What Is Intercropping
Intercropping is the method of growing two or more crops in any given space at the same time, with the goal of providing maximum benefits to each crop.
In intercropping, crops are grown in close proximity. This can be in the same row or bed, or in rows that are close enough to each other for the plants to biologically interact with each other in a beneficial way, in other words, you are planting to create a win-win situation for all the plants.
Companion planting, which is often mentioned in the same breath, is a form of intercropping. Plant selection in companion planting is based on how plants benefit—or potentially harm—each other when grown closely together. Companion planting is the most popular method of intercropping used in home gardens.
Benefits of Intercropping
There are two main benefits to intercropping: efficient use of resources, and natural pest control.
Planting crops together can help use light, water, and nutrients in a targeted and more efficient way than planting them separately. For example, tall crops with large leaves such as tomatoes and corn cast shade on plants that need protection from scorching midsummer sun and heat, such as lettuce.
Grouping crops according to their low or high water needs saves water because it avoids giving a crop more water than it actually needs. How you plant different crops also affects the nutrient uptake of plants and nutrient distribution in the soil. An example of this are legumes, which are known as “nitrogen fixers”. Beans, peas, and other legumes have the ability to convert nitrogen from the atmosphere into nitrogen in the soil, in a form that can be absorbed by plants.
Another main benefit of intercropping is that it reduces the need to use pesticides and insecticides.
The chemicals released by certain crops can discourage harmful insects. These can be strong-scented herbs like basil and mint, or members of the allium family like as garlic and onions; both act as broad-spectrum insect repellents.
Another option is to plant trap crops as a deterrent. This is accomplished by planting a crop that is more attractive to the pest to lure pests it away from the main crop. The insects will feed on the trap crop first, or gather on it so you can remove them manually. Trap crops can also be planted to attract nematodes and fungal diseases.
For trap crops, proper timing is crucial so that the trap crop is ready when the main, desirable crop is the most vulnerable to insect damage or feeding.
Intercropping can also attract beneficial insects to your garden. It provides food and shelter for predators such as parasitic wasps that plant their eggs on tomato hornworms. Increasing the number of natural enemies in your garden can help you avoid using synthetic pesticides.
How to Use intercropping in a Garden
When you select plants for intercropping, there are four things to keep in mind:
- The density of planting the seeds or seedlings
- The space that that crop takes up, how tall and wide will the plants be when mature
- The time to harvest, or the days to maturity
- The plant architecture, how much of the crop is aboveground, how much is root system, and how shallow are the roots
The three types of intercropping most relevant to home gardeners are:
1. Row intercropping where two or more crops are grown together and at least one of the crops is planted in rows. (In row intercropping both plants are grown in alternating rows)
2. Mixed intercropping without rows, which can be the most challenging in terms of maintaining crop rotation. (Seldom used in home vegetable gardens; an example would be radish and carrot.)
3. Relay intercropping where the growth cycle of the crops overlap with one variety ready for harvest quickly and the other requiring a longer growing season. Radishes and carrots are often grown this way. The radish seed sprouts early marking the plot for the carrots which take longer to germinate and mature enough to harvest.
Intercropping vs. Interplanting
The line between the two terms isn’t always clearly drawn; in fact, they are often used interchangeably. Interplanting is a form of intercropping, which is the all-encompassing term.
Interplanting is done with the goal of making the most use of the garden space. One approach is French intensive gardening. The above examples of planting carrots and radishes in the same row is interplanting, as is the practice of growing lettuce next to tomato plants where the lettuce uses the space that is not yet occupied by the tomatoes. The lettuce is harvested about the time the tomato foliage starts to occupy the entire space.
The difference between intercropping and interplanting is also fuzzy because when interplanting, the same considerations apply as in intercropping: the size of the plants, how densely they grow, how long they take to mature, and the plant architecture.
Wszelaki, A. Trap Crops, Intercropping, and Companion Planting. University of Tennessee Extension Service.