When preparing the soil, avoid fresh manure and organic materials or fertilizers high in nitrogen. An overly rich soil will encourage lush foliage at the expense of crisp, tasty roots.
When the seedlings are about two inches tall, thin the plants to three-inch spacings. If not thinned, you’re likely to end up with shriveled, inedible roots.
Mulch the radishes with compost enriched with wood ashes. This not only keeps root maggots at bay, but also helps the soil retain moisture that could mean the difference between perfect and pitiful radishes.
Water in moderation. If the soil is too dry, radishes will bolt and become pithy and too pungent to eat. If too wet, the roots will split and rot. Never let the soil dry out, but don’t keep it mucky, either.
Radishes are superb companion plants, particularly when used to draw aphids, flea beetles, and other pests away from peppers, squash, cukes, and other vegetables.