Watering and Feeding Radishes: Steady Moisture Stops Splitting

Water a little before it dries

When a swelling radish sitting in dry soil suddenly gets a heavy watering, the inside expands faster than the skin and it cracks open. The rule is to water little and often, before the surface turns pale and dry.

In the ground that usually means every two to three days; in containers, every day or every other day depending on how fast they dry. A simple test is to push a finger half an inch (1 cm) into the soil and water if it feels dry.

Go easy on fertilizer

Radishes are ready in three to four weeks, so with fertilizer worked in before sowing they rarely need more. Too much fertilizer grows lush leaves and leaves nothing for the root.

When preparing the bed, mixing in about 4 pounds of compost per 10 square feet (2 kg per square meter) and a small handful of balanced fertilizer is plenty. If the previous crop was well fed, compost alone will do.

1. Prepare the bed two weeks ahead Work in compost and fertilizer and wait two weeks before sowing. Fertilizer added just before sowing can burn the young roots.
2. Side-dress only at the second thinning Only if the leaves are pale, scatter a pinch between the rows and mix it into the soil. Never against the stems.
3. Skip unfinished compost Compost that has not fully broken down makes roots fork and attracts pests. Use only dark, crumbly, finished compost.

Check the sun and the airflow

Radishes will grow in part shade, but to fill out round roots they want four to five hours of direct sun a day. Without it the leaf stalks stretch and the roots stop at the size of a little finger.

On a balcony, avoid spots that spend much of the day in the shadow of the railing. Simply raising the pot onto a stand can add an hour or two of sun.

1. Count the hours of sun Check in the morning, at midday and in the afternoon and add up the hours in direct sun. Under four hours gives only thin roots.
2. Raise the container Set it on a stand or shelf to lift it out of the railing's shadow. The difference in the roots can be striking.

A bright windowsill indoors looks sunny but is not enough light. Radishes are more reliable grown outdoors.

Hill up soil to stop cracked, green shoulders

As radishes swell, their shoulders push up out of the soil. Left exposed they turn tough in the sun and become more prone to splitting with every swing in moisture. Drawing soil up against them each time you thin prevents both.

Hilling just means pinching soil from between the rows and pushing it against the plants. Covering the top of the root slightly is enough; bury it too deep and the base of the leaves rots.

1. Hill when shoulders show When the colored shoulder shows above the soil, push soil from between the rows against it until the top is just covered.
2. Do not bury the leaves Covering the base of the leaves traps moisture and causes rot. Cover only the root and leave the green leaf stalks in the open.

Containers need their own watering routine

A container holds little soil and can dry out in half a day of sun. Water it on the every-other-day schedule of a garden bed and the swings between wet and dry will split the roots. Make a habit of touching the soil each morning.

When you water, keep going until it runs out of the drainage holes. Frequent small sprinkles wet only the surface and never reach the roots. If the surface is damp but the plants look limp, the water is not getting to the bottom.

Where the container sits matters too. On bare concrete, heat from below dries it fast; raise it on slats or a stand to let air underneath and it dries more slowly.

1. Feel the soil each morning Push a finger half an inch (1 cm) in. If it is cool and damp, leave it; if it is dry, water.
2. Water until it drains Water until it runs into the saucer, then empty the saucer each time. Standing water starves the roots of air.
3. Twice a day in summer On hot days a morning watering can be gone by late afternoon. Check again before the leaves wilt and water if dry.

Never leave water standing in the saucer. Roots sitting in water run short of oxygen, so always tip it out after watering.

Working out why plants are struggling

All leaves and no root, roots that will not swell, roots too hot to eat. Radish problems can almost always be explained by water, fertilizer and light. Check them in order and you will know what to change next time.

1. Big leaves, thin roots Too much fertilizer or not enough thinning. Stop feeding and thin to two inches apart. Use less fertilizer at sowing next time.
2. Roots long instead of round Too crowded, or the soil is too hard. Thin wider, and next time dig the bed 8 inches (20 cm) deep before sowing.
3. Hot and stringy Dry soil and late harvesting together. Water more often and pull them while they are three quarters of an inch to an inch and a quarter (2 to 3 cm) across.
4. Yellow, tired leaves Out of food or out of water. Dig down to check: if it is dry, water; if it is moist, give a weak liquid feed.