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Garden Super Friends - Radish

Wednesday, 14 May 2014 01:00 Written by  R.S.N.

Today I want to reintroduce you to a humble spring and fall fast crop, one that just doesn't get the widespread attention other companion plants enjoy. It is another that follows the ROT “grows together, goes together” and the “goes together, grows together” spin-off sometimes applied to companion plants, but its uses spread beyond same-dish, same-harvest-time ease of access.

Radish – Speedy Snackable

First off, a tangent. If you already love the humble radish and its tops in more than salads, go ahead and skip down. I feel like the radish gets pigeonholed in its culinary use as well as neglected in the garden services it renders, so I have to try to make a couple converts before I move on to how it can aid in environmentally friendly growing, from planters to farm fields. 

People who “don’t like” radishes should step away from the pointy pink balls found on most salad bars. One, grocery store produce is never as good. Two, there are way, way better radishes in this world than the cherry variety on the general grocer’s aisle. 

Radishes come in a wide variety of sizes, growing times, and most importantly flavors. Some are super-duper crazy hot, but mild and sweeter heirlooms are also available. Big, long 45- and 60-day radishes like skinny white daikons are really better slow roasted and from autumn-sown crops, but any type of cooking can change their flavor and texture for people who were turned off by eating them raw. 

Radishes are also much, much milder and sweeter when grown in cool weather. They will absolutely tolerate some 30- and 28-degree weather, so they can usually be sown well before and after last and first frosts to get the best flavor.

Radishes aren't restricted to salads. Watermelon radishes are a big, pink daikon that don’t need cooked and are sweeter and milder than the typical red-skinned cherry-type radish. They pair excellently sliced with tomatoes under a drizzle of olive or sunflower oil, or can be grated into stir fry. They can also be grated and tossed into just-wilted or boiled greens for added texture and flavor. French breakfast and the watermelon variety above make awesome spinach-artichoke dip, hummus, and tzatziki dipper wedges alongside carrots, cucumber and celery (with and without crostini, chips, or pita). Any radish can be roasted alongside tubers, bulbs and winter squashes with herbs and a drizzle of oil (or duck/bacon fat – mmmmm).

So can their leaves. There are some smooth-leaf varieties, but many have a “furry” texture and can be downright uncomfortable to eat raw, although some can be sliced to tiny ribbons and added to oriental soups or stir fry in small quantity even so. I find radish leaves to be much, much better when cooked or at least blanched than when raw. 

The leaves are comparable in flavor to other mustards when wilted or boiled, and are chock full of vitamins and minerals, with calcium and Vitamin C notable among them. The leaves are reputed to have even more antioxidants than the root. 

Okay, done with the eating. Out to the container garden, yard, and fields for two fabulous ways radishes can save their neighbors and save the earth.

Trap Cropping

Radishes can be used to draw pests away from more vulnerable or more desirable leaves, especially smooth-leaf radish varieties like white icicle, red head, and pearl leaf (kimchee) radishes. Some insects don’t seem to mind the hairiness, so even prickly-leaf bog-standard radishes have value as a trap crop. Radishes seem to be particularly attractive to the lettuce and cabbage munchers of the world. 

Even in a mechanized setting, this trait can be utilized. If compartmentalized seed drills are available, radish can be set at long intervals (8-12”) along the side row, or congestion planted on the edge. To avoid losing space, radishes can be seeded in the verge in a single line right beside harvest crops. Because they’ll be left in place all season to serve their trap-crop function in those settings, developing to the point of a woody habanero while the desired lettuces and cabbages grow, rolling over them with machined during harvests or while under-planting a warm-season or overwintering crop just isn't a big deal. 

The same applies to home-scale row methods and smaller beds. Radishes destined to be sacrificed as trap crops by leaving them in the ground too long can be seeded beside rows and in or at the verges of walkways around beds. 

In non-commercial settings, radishes can also just be planted in the number desired for eating during cool weather, reseeding weekly or every two weeks to ensure there are always tasty tops for bugs to munch instead of lettuce and cabbage. A last crop can be left in for the season even after hot weather hits to help with pests like flea beetles. 

The roots themselves are little affected by insect damage to the leaves, even when those leaves end up looking like lace. Severe munching may delay growth by a week or two, but with proper spacing, temperature and watering, even radishes that are basically down to veins produce tasty roots for munching raw, roasting with other root crops, pickling, and sticking on salads. 

While most documentation about radishes as a trap crop revolve around biting, chewing, and sucking leaf pests, radishes can also help with below-the-soil-line pests. They have recently been studied as a trap crop companion for nematode-ridden sugar beets (a specific variety, not all types of radishes). Radishes may also attract root maggots away from broccoli. Broccoli-eating caterpillars are not impressed with radishes, and will still need dealt with separately.

Planting rows of radishes in between rows of leafy greens does not seem to have as much benefit in pest reduction, but it may have some impact, especially with narrow rows and in zero-bare-earth settings. Gaps of 2-4 feet between radishes and the desired pest-ridden crop have extremely limited or no effect on crop loss. 

To get the most use out of radishes as a trap crop, they have to be at a density to keep the pest fed. One or two radishes in the corners of a 4'x8’ bed or every 8-10 feet down the side of a row might help with a mild infestation, but for severe infestations, a solid line down the side of the row or bed, or a 1:1 ratio of plants up to a 1:1 ratio of total biomass may be needed for significant control.

Radishes are Tillers!

No, not really, not the way chickens and big chunks of metal are. However, like carrots and other root crops, radishes are used in no-till commercial settings to loosen soil, prevent compaction, and help prepare soil for other row or field crops. 

Radishes in particular excel at this due to their short growing season, and because they can be used as over-wintering crops in some climates. The same benefits can be reaped by home-consumption growers, although it can result in a lot of radishes to eat and pickle at one time. (Free-range “scraps” chickens will regularly eat radishes, if any birds are available.)

Radish seeds

When they’re all done being useful, radishes bolt into incredibly tall, leafy, thick stalks, all out of proportion for a radish root. They’ll eventually make short, pointy, undulating seed heads reminiscent of a pea or bean pod that grows pointing up and away from the delicate limbs. The pods are easy to collect once the plants start drying and going brown, and in dry environments can be left until the first start splitting. In wetter environment, the stalks and pods can be collected to sit in good circulation and dry. Once totally dry, the seed pods split easily. Nestled inside some soft, dry, squishy white foamy matter will be the seeds needed to replant radishes another year. They’re not quite as easy as dry beans or just squishing clover flowers to sprinkle out tiny seeds, but they’re much, much less messy and time consuming than tomatoes. 


There are innumerable plants and combinations out there that can improve a specific target crop’s flavor, produce an ideal micro-climate for a target crop, reduce pests, and improve yields. The best of them offer an additional yield themselves and serve multiple purposes. Some plants don’t get along, though, and it’s important to be aware of water and nutrient competition, shade cast and shade sensitivity, and crowding sensitivity, and to try and plant in guilds that put roots at different levels to be most successful. 

Mother Earth News features an expansive list of companions, and others can be found all over the internet, with greater and lesser degrees of testing and science, anecdotal evidence, and the remnants of bad science from the original bio-dynamic sensitive crystallization theory. County extension offices and master gardener programs can regularly help with organic, multi-purpose “solution” planting for local problems. 

About the Author: R.S.N. is a former Marine Corps combat correspondent with overseas experience. After the service, her interests turned to sustainability in growing and in maximizing the produce from small spaces.

Last modified on Monday, 05 May 2014 23:18
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