Radishes are among the easiest vegetables to grow in your garden. They can be ready for harvest in as little as 30 days, and they don’t require a lot of nutrients to be successful. As a result, they’re a great crop to grow early in the season, right before you plant your summer crops, and they can also grow in the same bed beside a larger crop as radish requires little space.
There are several different varieties of radish, ranging from the common and fast-growing cherry belles and French breakfast radishes to the much larger daikon and watermelon radishes. There are even perennial radishes in the form of horseradish.
You can plant radish as early as you’re able to prepare the soil. Radish seeds will germinate in temperatures as low as 4oC, although they will germinate and grow faster when temperatures exceed 10oC. This allows you to get a full harvest of radish from your garden before you plant most of your larger, heat-loving crops. Note that radishes are cool crops, so only plant them in the spring and fall – the heat of mid-summer will limit the size of the radish roots.
Radish should be direct-seeded in your garden. Find a spot that’s full sun if you want to harvest large roots and a spot that’s part shade if you want larger radish greens. Plant the radish seeds by cultivating the top 6” of soil and then adding compost, which will add nutrients and improve the soil texture, as radish requires well-draining soil. Plant your radish seeds ½” deep and 1” apart within rows that are at least 12” apart. As the seeds germinate, thin the seedlings within each row to approximately 2” of separation. Water the soil regularly to keep the soil constantly damp (but not sopping wet) until the seeds have germinated.
Although it isn’t required, we recommend draping row cover over the radish seeds as soon as you plant them. This helps retain moisture in the soil and, more importantly, blocks flea beetles from attacking your radish seedlings.
Radish seeds are quick to germinate as the soil warms, and most varieties are ready to harvest within four weeks of germination. Very little maintenance is required besides keeping the soil damp (not soaking wet) and watching for pests. If you are growing daikon radish or watermelon radish, add an all-purpose fertilizer (or a slightly phosphorus-heavy fertilizer) after 30 days to help the plant roots size up.
Pests and Diseases
Radish is in the brassica family, so it is very popular with pests. The most common pests are clubroot and flea beetles. Clubroot is a soil-borne fungus that is difficult to manage once it’s in your garden. It’s best to avoid it through crop rotation, and if any spot in the garden has experienced clubroot in the past, add lime to raise the soil pH level above 7.0 and avoid planting anything in the brassica family in that space for at least four years. For flea beetles, drape a fine-mesh row cover on top of the plants as soon as you seed them or dust the leaves with diatomaceous earth to prevent or reduce the damage.
Harvest your radishes based on the size of the roots. For the common cherry belle radishes, aim for roots that are approximately 1” in diameter, usually four weeks after germination. For larger daikon and watermelon radishes, you typically need to wait until 8-9 weeks after germination. If significant rainfall or heat waves are in the forecast, aim to harvest your radish a little bit early to prevent the roots from splitting.
Harvest your radish by simply pulling the entire plant out of the ground. Once you’ve harvested them, keep the plants out of the sun and cut the greens off to prevent the roots from going soft. Store the roots in a sealed bag in the fridge for 3+ weeks, and store the greens in plastic bags in the fridge for 3-4 days.
© Homestead Toronto / Derek Barber