How to grow radishes in your garden

Of all the vegetables I grow in my garden, radishes are the easiest to grow. Why? Two primary reasons. One, radishes grow fast and are ready to harvest in 3-5 weeks. Second, radishes are direct-seeded. In other words, there is no need to start seeds indoors and later transplant.

Radishes are a cool-season crop and a member of the brassica or cabbage family. They come in a variety of sizes, colors and types. The most popular radish is the garden radish that is spicy, crisp and round. Dikon, the Asian radish, is another variety that home gardeners can grow. Dikon is less spicy and the roots (radish) are long and slender.

Generally, I let one or two of my radishes go to seed. Radish flowers are dainty and beautiful. The focus of this post is on the garden radish. Let’s look at how to grow radishes in your garden.

How to grow radishes

• Timing: Radishes are a cool-season crop (55°F – 75°F) making spring and fall the best time to sow the seeds. The soil needs to reach a temperature of 40°F before planting. For a continuous supply of radishes, new seeds can be planted every one-three weeks. Hot weather can cause bitterness in the radish and slower growth.
• Light: Radishes grow well in full sun but can take partial shade in the afternoon.
• Soil: Radishes need soil that is well-drained and not compacted. A pH of 6-7 is best (to determine your soil pH, perform a soil test). Harvests will be better if you prepare your soil with the addition of compost. Loosen the soil at least 6-inches deep to give the radish space to grow.
• Spacing: Follow the guidelines on the back of the seed package for planting depth and spacing. General instructions are to dig a furrow ¼ to ½ inch deep and plant seeds 1 inch apart. Seedlings will emerge in 5-10 days. Here are three methods for direct seeding radishes:
  • Broadcast the seed over a prepared bed. This simply means sprinkling the seed on the ground and then lightly rake in the seed.
  • Use 1-inch chicken wire as a template/guide over a prepared bed. This method will take more time and may result in lower thinning requirements.
  • Dig a furrow as long as needed and plant radish seeds i-inch apart.

How to care for radishes

• Fertilizing: A side dressing of nitrogen, such as Blood Meal, can be added to the soil after the seedling emerges. This will encourage rapid growth.
• Watering: Radishes need a consistent 1-inch of water per week to develop strong roots. Sandy soil requires more frequent watering due to the fast draining nature of this soil type. Cracking of the radish bulb is a characteristic of inconsistent watering.
• Mulch: Organic mulches (e. g. straw, dry shredded leaves, wood chips) can be used to ensure that the ground retains moisture and maintains soil temperature. Apply 2-3 inches around the base of the plant.
• Thinning: Thinning is very important for radishes because a healthy root bulb will not develop if the plants are spaced too closely. While none of us like to thin out healthy seedlings, however, this is a must. I use a scissor and cut the seedling stem just above where it hits the soil.
• Companions: Common companion crops include peas, nasturtium, lettuce and cucumbers.
• Crop rotation: Practice crop rotation for all members of the brassica family (e.g. broccoli, cabbage, kale) to reduce disease. Do not plant radishes or other brassica’s in the same spot for three years. For more information on how to develop a crop rotation plan for your home garden, check out this post Crop Rotation for the home gardener.
• Seeds: Seeds can be saved for up to four years if kept in a cool dry plant. I keep mine in the refrigerator.

How to manage pests/problems

Because radishes grow so quickly, pests and diseases are not a major problem. However, there are a few pests to watch for.

• Small black flea beetles are a common pest of radishes. Flea beetle damage will manifest as small holes in the leaves.
• Root maggots are a small white pest that can burrow into the bulb and root.

In both cases, a floating row cover is your best protection. For more information about how to leverage row cover, check out this post How to use floating row cover in your organic garden.

In addition to pests, there are a few other problems to be aware:

• Cracking and splitting of the radish. This can be caused by letting the radish stay too long in the ground or by improper watering (too much or too little).
• Leafy green but no radish. This can be caused by improper thinning. Radishes need their space to develop properly.

How to harvest and store

Radishes mature in 3-5 weeks. You will begin to see the radish bulb break the top of the soil. The seed packet should describe the overall circumference of the radish. Pull a radish to see if it’s the right size.

After harvesting, follow this process:

• Cut the top leaves off the radish. The leaves are also edible.
• Clean in a bath of cold water
• Dry with dish or paper towels
• Place in a plastic bag
• Store in the refrigerator

Radishes will keep for 1-2 weeks if stored dry and at a refrigerated temperature of 32°F. As radishes age, they will become softer and lose their flavor.  

How to prepare

Radishes can be sliced and added to salads or can be eaten whole as a snack. I like to sprinkle radishes with a little salt and eat. Yum! The leaves of the radish are also edible as a leafy green.

Recommended cultivars

• Cherry Belle Radish – 25 days to maturity. Classic red garden radish.
• Holmes’ Royal Red – 25-30 days to maturity. Measuring 1-inch in diameter.
• Radiant Radish Mix – 35 days to maturity. Cherry Belle, French Breakfast, Purple Plum, and Easter Egg radishes.

Botanical Information

Garden radish

• Family:     Brassicaceae
• Genus:     Raphanus
• Species:  R. raphanistrum

References

• University of Minnesota Extension – Growing radishes in home gardens
• Cornell University – Radishes