8 Plants That Can Ruin Your Radish Crop, According to Gardening Experts

red, white, purple, and gold radishes freshly harvested from garden — Credit:
Barbara Rich/Getty Images

Radishes are well-known for their lightning-fast maturity (some varieties can go from seed to harvest in under 30 days!). But even though radishes are easy and quick to grow, they can be picky about their neighboring plants. Some plants compete with radishes for root space, others potentially shade radishes from the full sun they need, and others may hinder the growth of your radishes. Here you'll find a round-up of plants that gardening experts say to avoid growing near your radishes if you want a healthy, thriving crop.

Jane Gates, owner and principal designer at Gates & Croft Horticultural Design
Ken Johnson, horticulture educator at the University of Illinois and co-host of Good Growing

01 of 08

Corn

Growing corn (Zea mays) is one of the true delights of the garden, and there's no flavor fresher than that of a just-picked ear of corn. But one place corn doesn't belong is next to radishes. A mature stalk of corn is very tall and casts shadows, which could be detrimental to late-season radish plants that typically grow best in a full-sun environment.

02 of 08

Fennel

There are many reasons to love fennel (Foeniculum vulgare), but carefully consider where to plant it in your garden. Fennel is known for releasing allelopathic chemicals into the soil, inhibiting the growth of other vegetable plants. It's especially problematic for nightshades like tomatoes and peppers, but radishes can be affected, too.

03 of 08

Potatoes

Potatoes (Solanum tuberosum) look fairly tidy above ground, but underground is a different story. Their root system is impressive, which can be an issue if they're grown next to large, deep-growing radish varieties like daikon, says Jane Gates of Gates & Croft Horticultural Design. The soil requirements for potatoes and radishes are different, which is another reason to avoid planting them near each other.

04 of 08

Hyssop

Hyssop (Hyssopus officinalis) is a beautiful plant that attracts pollinators galore, but it's not a friend to radishes. "The most antagonistic plant you would want to avoid when planting radishes is the herb hyssop," says Gates. "This is one plant that will introduce a chemical into the surrounding soil that will deter some other plants, including radishes, from growing well." You can still enjoy hyssop's beauty and use it to attract pollinators, but plant it elsewhere in the garden.

05 of 08

Broccoli

As a member of the Brassicaceae family, radishes will do best if planted away from other plants in the same family, including broccoli (Brassica oleracea var. italica). "I would suggest keeping other related members of the brassica family—like cabbages, kale, broccoli, etc.—in areas of their own so they do not have to compete with radishes for the same soil nutrients," says Gates. Broccoli is also an allelopathic plant that releases chemicals in the soil, and these can inhibit the growth of your radishes.

06 of 08

Turnips

Turnips (Brassica rapa subsp. rapa) are another member of the Brassicaceae family. "Radishes are brassicas and will share many diseases and pests with other brassica crops like cabbage, broccoli, kohlrabi, and turnips," says horticulture educator Ken Johnson. "While these plants can be grown near each other, they should be monitored so pests and diseases don't spread from one crop to another." He recommends rotating the crops around the garden annually to help prevent the buildup of pests and diseases in one location.

07 of 08

Sunflowers

It's easy to see why you'd want to include tall and beautiful sunflowers (Helianthus spp.) in your garden. Those vibrant petals are spectacular, and each flower head produces an abundance of sunflower seeds. While you can still plant sunflowers in your garden, choose a location carefully. "Towering plants like sunflowers and corn—especially if grown on the south-facing side of vegetable and flower gardens—are likely to shade plants like the sun-loving radish," says Gates. "But these tall, vertical growers do best near the back of a garden anyway, where they can form an attractive backdrop or even double as handy poles for supporting edible vines like peas and beans."

08 of 08

Kohlrabi

Is there a more interesting-looking vegetable than kohlrabi? When you prepare to plant kohlrabi (Brassica olearcea var. gongylodes), remember that—like radishes—it's a brassica family member. These crops may compete for nutrients if planted next to one another. If you are concerned about your soil's nutrient levels, Johnson recommends conducting a soil test.