How to Grow Yamaimo Yamato

Wikimedia Commons

Yamaimo Yamato

Dioscorea japonica var. yamato

vegetable

Yamaimo Yamato is a Japanese mountain yam with long, slender tubers that can reach 3-4 feet in length. This cultivar is prized in Japanese cuisine for its mild flavor, sticky texture when grated, and nutritional benefits. It requires deep, well-prepared soil and a long growing season to develop properly.

When should you plant Yamaimo Yamato in your zone?

Get a personalized planting timeline — when to start seeds, transplant, and harvest — based on your USDA zone and local frost dates. Free to start.

Get my Yamaimo Yamato timeline →

Example Yamaimo Yamato timeline · Pittsburgh, PA (Zone 6b)

Plant Yamaimo Yamato
Around Apr 17

Near Pittsburgh's average last spring frost.
Tend & protect
Late spring–summer

Watering, feeding, and pest-watch reminders.
Harvest Yamaimo Yamato
Around Nov 8

≈ 240 days after planting

Sample dates for Pittsburgh, PA. Sign up to get exact Yamaimo Yamato dates for your own zip code.

Growing Conditions

☀️

Sun: Full sun, 6-8 hours daily

💧

Water: Moderate and consistent moisture; keep soil evenly moist but not waterlogged. Water 1-1.5 inches per week during growing season. Avoid drought stress and excessive moisture which can cause rot.

📏

Spacing: 12-18 inches

📅

Days to maturity: 240-270 days

🌱

Planting depth: Plant tuberlets or seed pieces 4-6 inches deep

Soil

Type: Deep, loose, well-draining sandy or sandy loam soil

pH: 6.0-7.0

Amendments:

Compost or aged manure Sand for improved drainage Perlite or coarse gravel

Growing Zones

Find your zone →

Thrives in zones 6-9 with cool to moderate summers

6a 6b 7a 7b 8a 8b 9a

Get my Yamaimo Yamato timeline →

Growth Stages

Sprouting

2-3 weeks

Initial emergence of shoots from planted tuberlets; first leaves appear above ground

Keep soil consistently moist and warm (60-70°F ideal). Protect from heavy rain and strong winds. Monitor for slugs and cutworms.

Vegetative Growth

8-12 weeks

Vine develops with heart-shaped leaves; vining growth extends along support structure; underground tuber begins to expand

Provide sturdy vertical support (trellis, stakes, or strings). Apply balanced fertilizer monthly. Mulch around base to retain moisture and regulate temperature. Remove weeds regularly.

Vigorous Vine Development

8-10 weeks

Extensive vine growth with dense foliage; aerial bulbils may form in leaf axils on some varieties; tuber continues underground elongation

Maintain consistent watering schedule. Support vines to prevent tangling and damage. Monitor for pests and diseases. Fertilize with higher potassium to support tuber development.

Tuber Maturation

6-8 weeks

Vine growth slows; foliage begins to yellow; underground tuber reaches full length and achieves proper texture and starch content

Reduce nitrogen fertilizer. Maintain steady moisture levels. Avoid soil disturbance around plants. Foliage yellowing signals approaching harvest readiness.

Harvest Ready

At harvest (late fall)

Vines completely senescent and dried; tuber is fully mature with firm, non-sticky exterior; starch conversion complete

Cease watering 1-2 weeks before harvest to firm tubers. Carefully excavate to avoid breaking long, delicate tubers. Handle gently during digging and storage.

Companion Planting

Plan your garden →

Plant with:

Beans Peas Lettuce Spinach Garlic Onions

Avoid planting near:

Potatoes Tomatoes Other Dioscorea species (cross-pollination concerns)

Common Pests

and
Hand-pick, use copper barriers, apply diatomaceous earth, or set beer traps
Create cardboard collars around seedlings, remove debris, use neem oil, or apply Bacillus thuringiensis
Hand-pick in early morning, use Japanese beetle traps away from plants, apply neem oil, or use kaolin clay spray
Remove affected leaves, improve air circulation, avoid overhead watering, apply sulfur or copper fungicide if severe
Ensure excellent drainage, avoid overwatering, improve soil aeration, use well-draining amendments

Uses

🍳

Traditional Japanese Cooking

Culinary

Yamaimo is a staple in Japanese cuisine, especially when grated into a sticky, glutinous paste used as a topping for rice, in soba noodle dishes (tororo soba), or mixed into soups. The tubers can also be sliced and grilled, steamed, or boiled. [source]

💊

Traditional Medicine & Digestive Health

Medicinal

In traditional Chinese and Japanese medicine, yamaimo is used to support digestion, improve nutrient absorption, and strengthen the spleen. Rich in diosgenin and other compounds with potential health-promoting properties. [source]

🍳

Nutritional Value

Culinary

Yamaimo is high in vitamins (B1, B6, folate), minerals (potassium, manganese), dietary fiber, and unique polysaccharides. Low in calories and fat, making it a nutritious addition to any diet. [source]

🏠

Mucilage & Slime Production

Household

When grated, yamaimo produces a distinctive slimy, mucilaginous coating due to its high starch and polysaccharide content. This slime is prized in Japanese cooking for its unique mouthfeel and texture. [source]

🎨

Home Garden Specialty Crop

Craft

Growing yamaimo is a rewarding specialty crop for home gardeners interested in Asian vegetables and traditional food production. The long vines also provide aesthetic interest and shade in the garden. [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 in late fall (October-November) after first frost when foliage completely dies back and vines turn brown. Carefully dig from the side rather than pulling to avoid breaking the long, fragile tubers. Use a long, narrow spade to excavate without damaging. Mature tubers can reach 3-4 feet long. Handle gently and cure in cool, humid conditions for 1-2 weeks before storage. Store in cool (50-60°F), humid conditions; they can last 2-3 months if kept properly.

Fun Facts

🌱 Yamaimo tubers are so delicate that they can take 8-10 minutes to excavate carefully from a 3-foot depth without breaking, making harvest a patient and meditative process in Japan.
🌱 The 'Yamato' cultivar specifically is prized in Nagano Prefecture, Japan, where it has been grown for generations and commands premium prices at markets due to its superior quality and mild flavor.
🌱 Yamaimo has been cultivated in East Asia for over 2,000 years and is mentioned in ancient Chinese medical texts as a longevity food.

Gardening Terms

New to gardening? Learn about terms used in this guide:

Cultivar Full Sun Mulch Trellis

Shop Yamaimo Yamato plants and related plants at Plant Addicts →

Join 30,000 gardeners planning their gardens with LizPlants.

Get your personalized Yamaimo Yamato planting timeline

Tell us your zip code and we'll calculate exactly when to start Yamaimo Yamato seeds, transplant seedlings, and harvest — based on your USDA zone and local frost dates. Includes calendar reminders and printable task lists. Free to start.

Get my Yamaimo Yamato timeline →