New to North America, this Japanese heirloom is a medium sized, oblong daikon type. The wasabi-green skin and flesh is crisp and succulent, with a strong heat reminiscent of the much loved Japanese horseradish paste. The flavour is sharp and tear-inducing for lovers of spice. Wasabi radish seeds also make excellent micro-greens, with the spiciness developing early on in its tiny leaves. Radishes can be grown all season but they're easiest when sown March/April and again August through October. Optimal soil temperature: 18-24°C (65-75°F). Seeds should sprout in 5-7 days.
Matures in 60 days. (Open pollinated seeds)
Time radish plantings one to two weeks apart for a longer harvest period. The secret to growing a great radish is to plant when the soil is cool, to not plant too close together, and to harvest promptly before the roots get woody and bitter. Every part of the radish is edible. Before they are fully mature, radish seed pods are tender and juicy with a wonderfully sharp flavour that is excellent in stir-fries and soups. The immature seeds themselves have a flavour and texture reminiscent of caviar. Continue reading below for our favourite tips on how to grow radishes from seed.
We Recommend: If you don’t already have a favourite, go for variety: The Easter Egg Mix (RD674) can’t be surpassed for showing everything a radish can be. Not only do you get a mix of colours, but you’ll come to appreciate subtle flavour differences, and differences in piquancy, or spiciness.
Season & Zone
Season: Cool season
Exposure: Full sun
Radishes can be grown all season but they’re easiest when sown just after the last frost date and again at the end of summer and into the fall. Optimal soil temperature: 18-24°C (65-75°F). Seeds should sprout in 5-7 days.
Sow seeds 5mm (¼”) deep, 25 seeds per 30cm (12″) in rows spaced 30-45cm (12-18″) apart, and thin to 6-12 plants per 30cm (12″).
Days to Maturity: From direct sowing.
Ideal pH: 6.0-6.8. Radishes are moderate to heavy feeders. Best in rich, loamy soil amended with composted manure. Add 1 cup of complete organic fertilizer for every 3m (10′) of row for background fertility. Lime beds the previous fall. The real secret to growing this little vegetable is speed. Sow a short row frequently, thin them quickly, keep them watered, eat them quickly, and sow some more.
Harvest promptly when radishes are the size of large marbles. The leaves and developing seedpods are also tasty.
In optimal conditions at least 80% of seeds will germinate. Usual seed life: 4 years. Per 100′ row: 1.2M seeds, per acre: 522M seeds.
Diseases & Pests
Root maggots and flea beetles can be a problem. Expect to lose 20-30% of your crop to maggots if you don’t use a floating row cover.
Plant radishes near beans, beets, celeriac, chervil, cucumber, lettuce, mint, parsnip, peas, spinach, squash, and tomatoes. Avoid planting near Agastache or potatoes. It is said that planting 3 or 4 icicle radishes around the mound where you plant squash, and allowing them to grow and bloom, will prevent most pests of squash and cucumber.
More on Companion Planting.