Grafting Tomato on Potato: Complete Guide for Gardeners

Yes, you can successfully graft tomato plants (Solanum lycopersicum) onto potato rootstock (Solanum tuberosum), creating a dual-crop plant that produces tomatoes above ground and potatoes below. This technique, known as "TomTato" or "Potato Tom," leverages the plants' shared Solanaceae family compatibility. With proper technique, gardeners can harvest both crops from a single plant, maximizing space efficiency in small gardens while potentially improving disease resistance.

The Science Behind Grafting Tomato on Potato

Grafting tomato onto potato works because both plants belong to the Solanaceae family, sharing similar vascular structures that allow for successful tissue union. Unlike genetic modification, grafting is a physical horticultural technique where the vascular tissues of two plants fuse together.

Researchers at the University of California's Agriculture and Natural Resources department have documented successful graft unions between compatible Solanaceae species. The key factor is ensuring the cambium layers (growing tissue just beneath the bark) of both plants align properly during the grafting process.

Benefits and Realistic Expectations

Grafting tomato on potato offers several advantages for home gardeners:

• Space efficiency - Grow two crops in the space of one plant
• Disease resistance potential - Potato rootstock may provide resistance to certain soil-borne tomato diseases
• Water conservation - Single root system serves both crops
• Novelty value - An engaging gardening project for enthusiasts

However, manage your expectations: grafted plants typically produce fewer tomatoes than standalone tomato plants, and potato yields may be slightly reduced. Success rates vary between 40-70% depending on technique and environmental conditions, according to research from Cornell University's School of Integrative Plant Science.

Factor	Standalone Tomato	Standalone Potato	Grafted Plant
Space Required	1 plant footprint	1 plant footprint	1 plant footprint
Tomato Yield	High	N/A	Moderate (30-50% less)
Potato Yield	N/A	High	Moderate (20-30% less)
Disease Resistance	Variety-dependent	Variety-dependent	Potential soil disease resistance

Best Timing and Plant Selection

The optimal time for grafting is during the plants' active growth phase, typically 3-4 weeks after germination when stems reach pencil thickness (approximately 1/4 inch diameter). Both plants should be at similar growth stages for best results.

For successful grafting, choose compatible varieties:

• Potato rootstock: Disease-resistant varieties like 'Russet Burbank' or 'Yukon Gold'
• Tomato scion: Determinate varieties work best, such as 'Celebrity' or 'Bush Early Girl'

Avoid using heirloom tomatoes with significantly different growth habits, as this reduces success rates. The Royal Horticultural Society notes that graft compatibility is highest between closely related cultivars within each species.

Step-by-Step Grafting Process

Follow these steps for successful grafting:

1. Prepare materials: Sterilized razor blade, grafting clips or rubber bands, rooting hormone (optional), humidity dome
2. Cut both plants: Make 45-degree angled cuts approximately 3-4 inches above soil line on both plants
3. Create graft union: Join the cut surfaces, ensuring cambium layers align (match the green growing tissue just beneath the bark)
4. Secure the graft: Use grafting clips or thin rubber bands to hold the union firmly in place
5. Protect the graft: Place under humidity dome for 7-10 days to prevent desiccation
6. Monitor healing: Gradually reduce humidity over 2 weeks as the graft heals

The critical healing period requires maintaining high humidity (80-90%) and moderate temperatures (70-75°F). Avoid direct sunlight during the first week. After 10-14 days, carefully remove the clips once the union has healed.

Aftercare for Grafted Plants

Proper aftercare ensures your grafted plant thrives:

• Watering: Maintain consistent moisture without waterlogging (potatoes prefer slightly drier conditions than tomatoes)
• Fertilizing: Use balanced fertilizer with higher potassium during fruiting stage
• Support: Provide sturdy support for tomato growth while allowing potato tubers to develop underground
• Monitoring: Check regularly for signs of graft failure or disease

One common challenge is managing the different water needs of tomatoes (which prefer consistent moisture) and potatoes (which can develop rot in overly wet conditions). The University of Florida IFAS Extension recommends using drip irrigation to maintain optimal moisture levels for both crops.

Troubleshooting Common Issues

Even with proper technique, you may encounter these issues:

• Graft failure: If the union doesn't heal, try again with younger plants and ensure perfect cambium alignment
• Reduced yields: This is normal - grafted plants typically produce less of each crop than standalone plants
• Disease transmission: Monitor for verticillium wilt, which can move from potato to tomato
• Water management: Adjust irrigation to balance the needs of both crops

Remember that grafting tomato on potato won't create a plant that produces tomatoes underground or potatoes on the vine - each crop develops in its natural location. The graft simply allows one root system to support two different above-ground and below-ground harvests.

When Grafting Isn't Recommended

While intriguing, this technique isn't suitable for all gardeners:

• Gardeners seeking maximum yields of either crop
• Those with limited time for the delicate grafting process
• Gardeners in extremely hot or humid climates (reduces success rates)
• Commercial growers focused on single-crop efficiency

For most home gardeners, the novelty and space-saving benefits outweigh the slightly reduced yields. As noted in research published in the American Journal of Plant Sciences, "The primary value of tomato-potato grafts lies in educational and small-space gardening applications rather than commercial production."

Can you really grow tomatoes and potatoes on the same plant?

Yes, through grafting, you can grow tomatoes above ground and potatoes below ground on the same plant. This isn't genetic modification but a physical joining of two plants from the same family (Solanaceae). The resulting plant, sometimes called 'TomTato,' produces regular tomatoes on the vine and regular potatoes underground.

What's the success rate for grafting tomato on potato?

Success rates typically range from 40-70% depending on technique, plant varieties, and environmental conditions. Factors that improve success include using plants of similar stem diameter, proper cambium layer alignment, maintaining high humidity during healing, and selecting compatible varieties. Commercial grafting operations achieve higher success rates through controlled environments and specialized techniques.

Do grafted tomato-potato plants produce less yield?

Yes, grafted plants typically produce 20-50% less of each crop compared to standalone plants. Tomato yields are usually reduced by 30-50% while potato yields decrease by 20-30%. This trade-off is the price for space efficiency. The plants must divide resources between fruit production above ground and tuber development below ground.

Which tomato varieties work best for grafting onto potato?

Determinate (bush) tomato varieties work best for grafting, such as 'Celebrity,' 'Bush Early Girl,' or 'Roma.' These varieties have more compact growth habits that better match potato plant energy requirements. Avoid large indeterminate varieties that require excessive energy for vine growth, as they often overwhelm the grafted plant's resources.

How long does it take for a tomato-potato graft to heal?

The critical healing period takes 7-14 days under ideal conditions. During this time, the graft union must be kept in high humidity (80-90%) with moderate temperatures (70-75°F) and indirect light. You'll know the graft has healed when new growth appears above the graft union and the supporting clips can be removed without the union separating.