banner ad
By January 19, 2018 0 Comments Read More →

What is Intercropping

Print Friendly, PDF & Email


Productive intercropping – spinach, cabbage and radish growing alongside in a raised bed.



Mark Abbott-Compton from Learn How to Garden takes advantage of intercropping to maximise plot space – a great technique for getting better harvests from smaller plots with minimum effort.

Intercropping ‒ or catch cropping ‒ is quite simply one of the best ways to maximise the amount of crops you can get from any garden bed. Intercropping takes advantage of the fact that while some vegetables take up to a year to be ready for harvesting, others can be ready in as little as 8‒12 weeks, and as those vegetables that take longer are obviously slower growing, we can interplant between them with faster-growing crops which will be harvested and removed well before the slower-growing plants eventually need the space.

In gardening speak, ‘intercropping’ can refer to planting underneath taller-growing crops to make use of space, or using the beneficial relationship that two specific crops can have when growing close to each other. However, the most common method of intercropping used to maximise crops is referred to as the Three Sisters method, whereby climbing beans are planted very close to tall-growing maize, and a trailing summer squash is planted between them.

The theory behind this is quite simple: as the maize grows, the climbing beans twine around it and use it for support; the squash growing between the maize and beans produces shade, reducing the evaporation of moisture in the soil, improving the crop by retaining water that all the plants can use; the beans, as they grow, extract nitrogen from the air and fix it on their roots in small nodules; this becomes available to both the maize and the summer squash that are growing, and is used by both plants to aid growth.

Unfortunately, in my experience, this method of growing maize, climbing beans and summer squash does not work that well in the UK climate, possibly because we just do not grow maize in our gardens, generally substituting sweetcorn in its stead, which is started later in the year, is a much finer and more delicate plant than maize, and doesn’t really have the strength to support normal climbing beans so is rapidly overpowered. Fortunately, however, there is an alternative method that we can use when growing sweetcorn, based on the Three Sisters method.

Beans and lettuce also make excellent bedfellows.

What we need to do is to start off our sweetcorn in modules as normal, then when it’s time to plant out, we plant them in a square. The reason for this is because the sweetcorn plants need to pollinate each other or you will not get any sweetcorn cobs at all ‒ planting in a square provides better pollination and cropping. We can then use the space between the sweetcorn to grow dwarf beans, which benefit the sweetcorn by fixing nitrogen from the soil, and the dwarf beans get support from the growing sweetcorn stems. You could then use sweet dumpling squash (a small, summer squash that will quite happily ramble between the sweetcorn stems) to provide shade for the sweetcorn roots.

Sweet dumpling squash.

Another way of interplanting is to plant a green manure between tall-growing vegetables such as sweetcorn. Trefoil is such a green manure and can be sown when you are planting out sweetcorn by simply broadcasting the seed between the sweetcorn plants. Trefoil is low growing, has excellent weed-suppressing properties, fixes nitrogen and, if allowed to flower, attracts bees and other beneficial insects to the area, which will in turn pollinate other veg crops, and when the sweetcorn has finished, the trefoil can then be incorporated into the growing bed. By interplanting trefoil you are effectively improving the fertility of the soil in your veg beds for the long term.

Cropped sweetcorn grown with trefoil.

One way you can use climbing beans is to utilise the space in the centre of a growing frame. Most gardeners grow tall beans using a tunnel method involving two rows of beans planted along either side of a bed about 1m apart, which grow up supports at either side of the bed to create a tunnel in between. This space in the centre of the bed can then be intercropped not just once, but twice. You can use the space to plant out an early, fast-growing radish, which will have cropped well before the climbing beans have become too tall and shade the middle of the bed. You can then intercrop with spinach and lamb’s lettuce once the beans are growing up their supports, as these two crops will grow quite happily in the shady conditions provided by the beans. Obviously, you will not get quite such a heavy crop as you might if growing in open ground, but because the crop is really an extra bonus, it’s always well worth doing.

Unobtrusive, low-lying lamb’s lettuce.

If you are using a deep bed, or have created bean trenches, you could plant either a single squash or a single courgette plant at either end of the bean frame ‒ this will allow the plant to take advantage of the soil preparations you have already made for your beans, and will still allow the plants to have the good light levels needed for growth, as the beans will not be too large. Squash and beans both like deeply cultivated soil with plenty of moisture-retentive compost added to the bottom of the trenches.

Courgette and beetroot sharing a bed.

Perhaps the real classic intercropping technique is to use radishes in between rows of parsnips to mark out precisely where the parsnips have been planted. This is done because parsnips take a long time to germinate, and it allows you to do some hand-weeding to remove any weeds that may germinate before the parsnips germinate. Radishes grow very quickly and will be harvested a long time before the parsnips are ready.

A slightly different way of using radish as a means of intercropping is to station sow the parsnips, sowing three parsnip seeds 15‒20cm apart. In between the parsnip seeds you can then sprinkle a tiny amount of radish seed in rows. You can then plant lettuce later on as a catch crop between the rows of parsnips ‒ however, it’s important when doing this to use the ‘chessboard planting’ system.

‘Chessboard planting’ is simply a way of referring to how we plant our crops. Imagine the bed you are planting into as a chessboard, and plant only on the black squares so the rows in between are staggered. This allows the plants to develop much better, as they all have more space to grow.

Intercropping can also make use of any space both under and in between any tall brassicas such as Brussels sprouts, purple sprouting broccoli or flower sprouts, which all grow on tall individual stems. Under these tall brassicas we can then plant lettuce in between, all cropping before the brassicas are mature. Then, once the brassicas develop and there is sufficient height on the stem to allow light underneath, it is the ideal time to plant out spinach, pak choi, lettuce, spring onions or radishes, all of which will thrive in the semi-shade and tend to grow well later in the season.

Spring cabbages growing alongside taller brassicas.

A bed of spring cabbages can also be treated in just the same way as when intercropping other vegetables. Simply plant your spring cabbages out in rows, then, as they grow, remove alternate plants as spring greens to allow ‘chessboard plantings’ to develop; the cabbage remaining will then grow firm heads for cropping later in the season. When eventually cropping the cabbages, rather than removing the plants from the growing bed, simply cut the heads off, then cut a ‘cross’ into the top of the stump, which will encourage the development of a second flush of edible leaves, using the ability of the cabbage to grow in different ways to achieve maximum cropping from the space used and number of plants sown.

We probably don’t even think about it but we are interplanting whenever we fill a bed with different lettuces!








Post a Comment

Pin It on Pinterest

Share This