Radishes are a cool weather crop and can be started in the home garden up to seven weeks before the last Spring frost is expected. (To find the last spring frost date in your area, visit https://www.almanac.com/gardening/frostdates). Through most areas of the US, the best time to plant radishes from seed is April or May.
Because they love cool weather, radishes are often planted along with potatoes, lettuce, and peas in the early spring. Radishes mature quickly, in as little as 25 days for small radishes, so they are often the first spring vegetable that are ready to eat.
Tips for Growing Radishes
Radishes should be planted ¼ to ½ inch deep. The seeds are sown directly in the vegetable garden, rather than started indoors. Radishes prefer a sunny spot to grow and the soil pH is best between 6 and 7.5.
Space the radish plants at least 1 ½ inches apart. Radishes love water, so keep the soil moist. This is usually not difficult during the rainy spring season. If left in the ground long enough, some radishes will grow to over a pound in weight.
Large radishes become tough. Many people prefer to eat radishes when they are small. Space the radishes according to how big you plan to grow them.
Radishes are not prone to diseases. Occasionally, they will be bothered by root eating pests. Rotating the location of your radishes in your garden will help prevent this problem from occurring.
Covering Radishes During a Frost
Radishes can be planted early, but if there is frost in the forecast, it is best to cover them overnight. Make-shift garden cloches are a great way to do this. To make a garden cloche, turn a repurposed plastic container, such as a milk jug, or ice cream bucket upside down and gently tap the top into the ground around the tiny plants.
A garden cloche can also be made to cover entire rows, by making a frame out of wood or plastic and covering it with sheets of plastic. In a pinch, we’ve used old blankets to cover patches before, too.
Kids and Growing Heirloom Radish Seeds
Radishes are a very forgiving vegetable to grow and they mature quickly, making it the perfect first vegetable for beginning gardeners. Kids will enjoy growing heirloom radish seeds, which come in a variety of colors.
The Choiggia variety, for example, dates back to the 1840s and displays red and white rings inside the beet itself. The Detroit Dark Red variety has a deep red, globe-shaped root. It is the most popular variety in the US and dates back to 1892. The Golden Detroit variety has an orange colored root and has a very sweet flavor for a radish.