Growing Watermelons in Containers: Big Harvest, Small Space
Watermelons are a favorite summer treat, but many assume they require vast garden spaces. The good news is that you can grow them in containers, even on a balcony or patio. With the right variety, soil, and care, you can enjoy fresh, juicy watermelons from a small space.
Choosing the Right Watermelon Varieties for Containers
Not all watermelon varieties will thrive in containers. Look for smaller, bush-type varieties that are specifically bred for container gardening:
- Sugar Baby: A popular choice for containers, producing 8-10 lb. melons.
- Golden Midget: A small variety with sweet, golden flesh, weighing about 3-5 lbs.
- Black Diamond: A heart-shaped variety that grows well in containers.
These varieties are well-suited for container gardening due to their compact size and manageable growth habits.
Selecting the Right Container
When growing watermelons in containers, choose a large enough container to support the plant's root system and fruit growth:
- Size: At least 12-15 gallons (55-68 liters) per plant, but larger (20+ gallons) is better.
- Material: Plastic or fabric pots that allow for proper drainage and aeration.
- Drainage: Ensure the container has drainage holes to prevent waterlogging.
If using a barrel or large bucket, cut holes near the bottom for drainage.
Preparing the Soil for Container Watermelons
Watermelons thrive in well-draining, fertile soil. Use a high-quality potting mix with added compost or organic matter:
- Mix 60% potting soil with 30% compost and 10% perlite or vermiculite for better drainage.
- Avoid garden soil, which can compact and retain too much moisture.
- Pots can dry out quickly, so water regularly during hot, dry weather.
Planting Watermelon Seeds or Seedlings
You can start watermelons from seeds or transplant seedlings:
- Seeds: Sow 2-3 seeds per container, 1 inch deep. Thin to the strongest seedling after germination.
- Seedlings: Transplant when seedlings have 3-4 true leaves, ensuring the soil is warm.
Watermelons need warmth to grow, so wait until soil temperatures reach at least 70°F (21°C) before planting.
Providing Optimal Growing Conditions
Watermelons are demanding plants that require full sun, warmth, and consistent watering:
- Sunlight: At least 6-8 hours of direct sunlight daily.
- Temperature: Ideal growing temperature between 70-85°F (21-29°C).
- Watering: Keep soil consistently moist but not waterlogged. Water deeply at the base.
Check moisture levels by sticking your finger 2 inches into the soil; water if dry.
Supporting Vines and Fruits
As watermelon vines grow, they may need support:
- Use a sturdy trellis or cage to help manage vine growth and keep fruit off the ground.
- Smaller varieties may not require trellising, but larger ones will benefit.
- Gently tie vines to the trellis as they grow to prevent breakage.
If growing without a trellis, place a soft surface (like a towel or board) under the melons to prevent damage.
Fertilizing Container Watermelons
Watermelons are heavy feeders, so regular fertilization is key:
- Use a balanced, water-soluble fertilizer (10-10-10 or 20-20-20) every 2-3 weeks.
- Reduce nitrogen after fruit set to encourage sweetness.
- Organic options like fish emulsion or compost tea are also effective.
Over-fertilizing can lead to excessive foliage at the expense of fruit production.
Harvesting Watermelons From Containers
Knowing when to harvest is crucial for the best flavor:
- The underside of the melon will turn from white to yellow when ripe.
- The tendril nearest the fruit will dry and turn brown.
- A deep, hollow sound when tapped indicates ripeness.
Harvest by cutting the stem with a sharp knife, leaving a small piece attached to the fruit.
Common Problems and Solutions
- Poor Pollination: Hand-pollinate flowers with a small brush if bees are scarce.
- Powdery Mildew: Ensure good air circulation and treat with neem oil if needed.
- Small Fruit: Too many melons per vine can stunt growth—remove excess fruit.
Monitor plants regularly for pests like cucumber beetles and aphids, treating with insecticidal soap if necessary.
Storing Container-Grown Watermelons
Store harvested watermelons at room temperature, away from direct sunlight, for up to a week. For longer storage, place in a cool, dry place.
Cut melons should be refrigerated and consumed within a few days for the best quality.