Radish Seeds - Watermelon Radish - Raphanus sativus

2, 3, 4, 5, 6, 7, 8, 9, 10, 11

USDA Zones 2-11 - The Watermelon Radish is a cool-season root vegetable grown as an annual in all zones. Success is highly dependent on timing the planting so the root develops and matures during cool weather.

Best performance in All Zones when sown in late summer for a fall harvest. Maturing in the cool, shorter days of autumn prevents the plant from bolting (going to seed) and produces large, sweet, and mild-flavored roots.

Northern Zones (2-6) - Plant in mid-to-late summer (July through August) for a fantastic fall crop. A spring planting is possible but can be challenging, as the radish must reach full size before the summer heat arrives.

Hot Climate Zones (7-11) - This is a premier fall and winter garden crop. Plant seeds in late summer to early fall. For Central Texas, the ideal planting window is from late August through September. This allows the roots to mature during the mild fall and winter months, avoiding the intense heat that causes bitterness and bolting.

Soil Temperature - Germinates well in soil temperatures from 50F to 75F. An optimal range of 60-70F will ensure quick sprouting and strong establishment for the fall growing season.

Growing Season - This is a larger daikon-type radish and requires more time than small globe radishes, typically 60-70 days from seed to maturity.

Learn more about USDA Hardiness Zones here

Planting Watermelon Radish Seeds
Growing these stunning radishes is easy when you get the timing right. They are the perfect crop to plant for a delicious fall harvest.

When to Plant
This is a cool-season crop that is best planted for a fall harvest.

For a Fall Harvest (Ideal): The best time to plant is in late summer or early fall, about 8-10 weeks before your first expected fall frost. For gardeners in Texas and other southern regions, right now (mid-to-late August) is the perfect time to sow seeds for a harvest in October and November.

For a Spring Harvest: Direct sow seeds as soon as the soil can be worked in early spring. This is a race against the heat, as the plant may bolt if temperatures get too hot before the root fully sizes up.

Where to Plant
Sunlight: Choose a location that receives full sun (at least 6-8 hours a day).

Soil is Key: Watermelon radishes need loose, deep, well-drained soil to allow their large roots to grow without obstruction. If you have heavy clay, amend the area generously with compost to lighten the soil texture. Remove any rocks or hard clumps.

How to Plant
Prepare the Soil: Work the soil to a depth of at least 8-10 inches until it is fine and loose.

Sowing: Plant seeds 1/2 inch deep.

Spacing: Sow seeds about 1-2 inches apart in rows that are 12-18 inches apart.

Watering: Water the area well after planting and keep the soil consistently moist for good germination, which typically takes 5-10 days.

Thinning is CRITICAL: This is the most important step for growing large radishes. When the seedlings are 2-3 inches tall, you must thin them to stand 4-6 inches apart. Without this space, the roots will not have room to swell and will be small and misshapen.

Care & Maintenance
Watering: Provide consistent, even moisture throughout the growing season. About 1 inch of water per week is ideal. Inconsistent watering can cause the roots to split or become woody.

Weeding: Keep the area well-weeded to reduce competition for water and nutrients. A light mulch can help suppress weeds and retain moisture.

Fertilizing: These radishes are not heavy feeders. Amending the soil with compost before planting is usually all they need. Avoid high-nitrogen fertilizers, which will encourage lush leaves but small roots.

How to Harvest
Check for Size: Begin checking your radishes around 60 days after planting. The "shoulders" of the root will begin to push up out of the soil. They are ready when they are between 2 and 4 inches in diameter.

Harvesting: Gently loosen the soil around the root with a garden fork and pull it from the ground.

Don't Wait Too Long: Harvest them promptly once they reach a usable size. Radishes left in the ground for too long can become tough, woody, or pithy.

Enjoy the Greens: The leafy tops are also edible and can be harvested and cooked just like any other garden green.