How to Grow Showa-no-Sakae
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Showa-no-Sakae
Ipomoea batatas 'Showa-no-Sakae'
vegetableShowa-no-Sakae is a Japanese sweet potato variety prized for its striking purple-red skin and vibrant purple flesh. Known for its sweet flavor and high nutritional content, it produces reliable yields and is increasingly popular in home gardens and specialty markets. The ornamental foliage and productive vines make it attractive as both a food crop and landscape plant.
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Example Showa-no-Sakae timeline · Pittsburgh, PA (Zone 6b)
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Plant Showa-no-Sakae
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 Showa-no-Sakae
Around Jul 26≈ 100 days after planting
Sample dates for Pittsburgh, PA. Sign up to get exact Showa-no-Sakae dates for your own zip code.
Growing Conditions
Soil
Growing Zones
Find your zone →Thrives in zones 7-11; requires warm, frost-free growing season of at least 120 days
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Get my Showa-no-Sakae timeline →Growth Stages
Slip Establishment
2-3 weeksYoung rooted slips are planted and develop initial root system; small leaves emerge from the planted vine section
Keep soil consistently moist but not waterlogged; mulch around base to retain moisture; protect from strong winds and intense sun initially; ensure soil temperature is at least 60°F
Vegetative Growth
4-6 weeksVines rapidly extend with heart-shaped leaves; above-ground biomass develops; purple-tinged foliage becomes prominent
Maintain regular watering and monitor for nutrients; provide support or trellising if desired to control sprawl; allow vines to run on ground for optimal tuber development; manage weeds
Flowering
Throughout mid to late season, intermittentSmall morning-glory-like flowers appear in white, pink, or purple; flowering is optional and non-essential for tuber production
Flowering is indicative of mature vines but doesn't require intervention; continue standard watering and care; flowers may produce seeds but focus remains on tuber enlargement
Tuber Development & Bulking
6-8 weeksBelow ground, tubers enlarge and accumulate starches and sugars; skin thickens and deepens in color; vines continue to spread
Maintain steady moisture; reduce nitrogen to prevent excessive vine growth at expense of tubers; avoid disturbing soil around plants; side-dress with balanced fertilizer mid-season if needed
Maturity & Harvest Readiness
2-3 weeks before harvestTubers reach full size (6-12 inches); purple flesh becomes denser and sweeter; vines may show slight senescence; tuber skin is firm and vibrant purple-red
Reduce watering gradually in final 2-3 weeks to concentrate sugars and cure skin; monitor soil temperature; harvest before first frost; avoid bruising during harvest to prevent decay
Companion Planting
Plan your garden →Plant with:
Avoid planting near:
Common Pests
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Use reflective mulch, yellow sticky traps; spray neem oil or insecticidal soap; encourage natural predators
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Remove infested tubers immediately; practice crop rotation; use pheromone traps; store tubers at 55°F or below
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Row covers on young plants; kaolin clay spray; neem oil; encourage parasitic wasps
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Increase humidity; spray with water; neem oil; sulfur dust in hot conditions
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Ensure good air circulation; avoid overhead watering; remove affected leaves; apply copper fungicide if severe
Uses
Roasted and Baked Dishes
CulinaryShowa-no-Sakae's purple flesh and sweet flavor make it ideal for roasting, baking, and mashing. The dense, starchy tubers hold their shape and develop enhanced sweetness when cooked, making them popular in Japanese traditional desserts and modern gourmet cuisine. [source]
Antioxidant-Rich Superfood
MedicinalThe purple flesh contains anthocyanins and polyphenols, powerful antioxidants that support cardiovascular health and reduce inflammation. Regular consumption may help regulate blood sugar levels and provide immune-boosting benefits. [source]
Nutritional Staple
HouseholdRich in vitamins A, C, and potassium, as well as dietary fiber. Showa-no-Sakae provides excellent nutritional value as a whole food staple in balanced diets. [source]
Ornamental Garden Plant
CraftThe heart-shaped leaves and purple-tinged vines create an attractive ornamental display in gardens. The plant's vigorous growth habit and unique coloring make it popular in landscape and container gardens for aesthetic appeal alongside food production. [source]
Pollinator Attraction
WildlifeThe morning-glory-like flowers attract bees, butterflies, and other pollinators, making the plant valuable for supporting garden biodiversity. The flowering stage contributes to a healthy ecosystem in the growing space. [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 100-120 days after planting, after the first frost date has passed or when night temperatures consistently drop below 60°F. Dig carefully to avoid bruising tubers; use a garden fork to loosen soil before pulling vines. Leave tubers in a warm (75-85°F), humid location for 7-10 days to cure and toughen skin before storage. Store at 55-60°F in a dark, well-ventilated space; avoid refrigeration. Properly cured tubers can store 4-6 months.
Fun Facts
- 🌱 Showa-no-Sakae is a cultivar developed in Japan where purple sweet potatoes have been cultivated for centuries and are deeply embedded in traditional cuisine and health practices.
- 🌱 The purple pigmentation comes from anthocyanins, the same compounds that give blueberries their color; some researchers study purple sweet potatoes for potential anti-cancer and anti-inflammatory applications.
- 🌱 Sweet potato vines are so vigorous that a single plant can cover 200+ square feet if allowed to sprawl, making them excellent for weed suppression and living mulch in diverse plantings.
Gardening Terms
New to gardening? Learn about terms used in this guide:
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