How to Grow Double Diamond Watermelon
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Double Diamond Watermelon
Citrullus lanatus 'Double Diamond'
vegetableDouble Diamond is a hybrid watermelon variety known for its exceptionally sweet, crisp red flesh and high sugar content. It produces medium-sized, oval fruits with dark green skin and distinctive striping. This variety is prized for its consistent quality, disease resistance, and excellent flavor profile.
When should you plant Double Diamond Watermelon in your zone?
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Example Double Diamond Watermelon timeline · Pittsburgh, PA (Zone 6b)
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Plant Double Diamond Watermelon
Around Apr 17Near Pittsburgh's average last spring frost.
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Tend & protect
Late spring–summerWatering, feeding, and pest-watch reminders.
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Harvest Double Diamond Watermelon
Around Jul 1≈ 75 days after planting
Sample dates for Pittsburgh, PA. Sign up to get exact Double Diamond Watermelon dates for your own zip code.
Growing Conditions
Soil
Growing Zones
Find your zone →Thrives in zones 4-10, with best performance in zones 6-9
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Seedling
2-3 weeksEmerge with cotyledons; develop first true leaves within 7-10 days. Seedlings are tender and vulnerable.
Keep soil consistently moist but not waterlogged. Provide 12-16 hours of light daily if starting indoors. Maintain 70-75°F. Thin to strongest seedling if starting in clusters.
Vegetative Growth
3-4 weeksVigorous vine growth with multiple stems branching. Leaves are large, lobed, and deeply veined. No flowers yet.
Begin training vines on trellises if space is limited. Mulch around base to retain moisture and suppress weeds. Feed with balanced fertilizer every 3 weeks. Monitor for pests.
Flowering
2-3 weeksYellow flowers appear on vines; male flowers typically appear first, followed by female flowers (identifiable by small fruit behind flower). Bees become essential.
Ensure adequate pollination by attracting bees or hand-pollinating. Reduce nitrogen fertilizer to encourage fruiting over vegetative growth. Keep consistent watering.
Fruiting & Development
3-4 weeksSmall fruits develop behind flowers and expand rapidly. Skin darkens and develops characteristic striping. Fruit reaches full size before sweetening begins.
Thin to 1-2 fruits per vine for larger, sweeter melons. Apply straw under fruit to prevent rot and ground contact. Maintain steady water supply. Side-dress with potassium-rich fertilizer.
Maturation & Harvest
1-2 weeksFruit reaches full size; skin becomes deeply colored with bold striping. Tendril nearest fruit stem dries and browns. Ground spot turns creamy yellow. Interior develops characteristic red color.
Check daily for ripeness. Reduce watering in final week to concentrate sugars. Look for dull finish (not shiny) on skin, which indicates ripeness.
Companion Planting
Plan your garden →Plant with:
Avoid planting near:
Common Pests
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Use row covers on seedlings, apply neem oil or spinosad at first sign, plant trap crops like nasturtium, remove affected leaves
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Increase humidity by misting, spray with strong water stream, apply insecticidal soap or neem oil, encourage predatory mites
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Improve air circulation, apply sulfur or potassium bicarbonate fungicide, avoid overhead watering, remove infected leaves promptly
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Wrap base of vines with aluminum foil, inject Bt into hollow stems, plant succession crops, remove affected vines immediately
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Spray with strong water spray, use insecticidal soap, apply neem oil, encourage beneficial insects like ladybugs, use reflective mulch
Uses
Fresh eating and desserts
CulinaryDouble Diamond's exceptional sweetness and crisp texture make it ideal for eating fresh, cutting into fruit salads, or blending into smoothies and beverages. [source]
Grilling and cooking
CulinaryThe firm flesh holds up well when grilled with light char marks, added to salads with feta, or used in gazpacho. [source]
Seeds for planting
HouseholdSave seeds from mature melons for next season's planting, though hybrid varieties may not produce identical offspring. [source]
Pollinator support
WildlifeThe abundant yellow flowers attract bees and other pollinators throughout the growing season, supporting garden biodiversity. [source]
Hydration and nutrition
MedicinalWatermelon is 92% water and contains lycopene, vitamins A and C, and citrulline, which supports cardiovascular health and hydration. [source]
This is not medical advice. LizPlants is not a medical resource. Always consult a qualified healthcare professional before using plants medicinally.
Harvest Tips
Harvest when skin shows deep coloring with bold dark and light striping, the bottom spot turns creamy yellow, the melon sounds hollow when thumped, and the nearest tendril is dry and brown. Cut stem with sharp knife rather than pulling. Peak sweetness occurs at full maturity. A ripe melon should feel heavy for its size. Store at room temperature for 1-2 weeks or refrigerate for up to 3 weeks.
Fun Facts
- 🌱 Double Diamond watermelons can weigh 12-16 pounds and are excellent for farmers markets due to their striking appearance and exceptional taste.
- 🌱 Watermelons are technically berries (pepos) with a hard rind, not melons or gourds—the thick skin develops from the flower's ovary wall.
- 🌱 The crisp 'crunch' you hear when cutting a ripe watermelon is caused by the shattering of crisp cell walls due to high water content and cellular structure, which is actually a sign of peak ripeness.
Gardening Terms
New to gardening? Learn about terms used in this guide:
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