Grafting joins a tomato rootstock to a tomato scion to combine disease resistance with fruit quality
Grafting is the practice of joining the top growth of one tomato plant (the scion) to the root system of another (the rootstock). The rootstock is chosen for disease resistance or vigor; the scion is chosen for the fruit you want to harvest. When done correctly, the two fuse into a single plant that produces your preferred tomato while resisting soil-borne diseases like fusarium wilt or verticillium wilt that might kill an ungrafted plant in the same soil.
Home gardeners graft tomatoes for two main reasons: to grow heirloom or specialty varieties in soil where disease has made them impossible to grow, or to extend the season by using a vigorous rootstock that produces fruit earlier and longer. Commercial growers graft almost all their plants. The technique takes practice but is learnable in a season.
Key Takeaways
- Grafting requires starting seeds of both rootstock and scion varieties at the same time so they reach the right size on the same day.
- The most reliable home method is splice grafting, where you make a single angled cut through both stems and bind them together with a clip or tape.
- The graft union must stay warm and humid for 7 to 10 days while the cut surfaces fuse; a propagation mat and humidity dome work well.
- After the graft heals, you remove the rootstock leaves and grow the plant as normal, but the roots remain the original disease-resistant variety.
- Grafted plants cost more to produce but often outperform ungrafted plants in disease pressure and total yield over a season.
Choose your rootstock and scion varieties before you plant seeds
The rootstock is the plant whose roots you will keep. Choose a variety bred for disease resistance to the problems in your soil or region. Common rootstocks include 'Maxifort', 'Beaufort', and 'Iron Lady'—all resistant to fusarium and verticillium. Your seed supplier or local extension office can tell you which diseases are present in your garden soil; a soil test costs $15 to $40 and identifies the specific pathogens.
The scion is the variety you want to eat. This can be any tomato—heirloom, hybrid, cherry, paste, or beefsteak. The scion contributes the fruit; the rootstock contributes only the roots and lower stem.
Start seeds of both varieties on the same day, 4 to 6 weeks before your last spring frost. They must reach the right size at the same time. The ideal grafting size is when the stem is about the thickness of a wooden toothpick (roughly 3 to 4 millimeters) and the plant has 4 to 6 true leaves. This usually takes 5 to 7 weeks from seed, depending on light and temperature.
Prepare your workspace and tools on grafting day
Grafting works best in a clean, well-lit space. You will need a sharp, clean knife—a single-edge razor blade or a grafting knife works well. Sterilize the blade with rubbing alcohol or a 10 percent bleach solution (one part bleach to nine parts water) and let it air-dry. A contaminated blade can introduce rot at the graft union.
Have ready a supply of grafting clips, grafting tape, or parafilm tape to hold the graft together. Grafting clips are small plastic clamps designed for this purpose and cost $0.10 to $0.30 each. Parafilm is a stretchy tape that seals the cut and is often easier for beginners. You will also need a propagation mat set to 75 to 80 degrees Fahrenheit and a humidity dome or clear plastic bag to keep the graft moist while it heals.
Work in a calm environment. Rushing increases the chance of a poor cut or contamination. Most home growers graft 10 to 20 plants at a time, which takes 30 to 60 minutes once you have the rhythm.
Make the graft cut using the splice method
Splice grafting is the most reliable method for home growers. Hold the rootstock plant in one hand. Using your sterilized blade, make a single angled cut (about 30 degrees) upward through the stem, roughly 1 to 2 inches above the soil line. The cut should be clean and smooth, about 1 inch long. Remove the top of the rootstock plant above the cut and discard it.
Now prepare the scion. Cut the bottom of the scion stem at the same angle, creating a matching cut surface about 1 inch long. The two cut surfaces should fit together snugly, like two puzzle pieces. If the scion is thicker than the rootstock, angle the cut so that at least one edge aligns perfectly—the cambium (the green layer just under the bark) must touch on at least one side for the graft to fuse.
Slide the scion onto the rootstock so the cut surfaces meet. The fit should be tight enough that the pieces do not slide apart on their own. If the fit is loose, the graft will fail. when ready find the joint with a grafting clip, parafilm tape, or grafting tape, wrapping around the stem two or three times to hold it firmly in place.
Keep the graft warm and humid while it heals
Place the grafted plant on a propagation mat set to 75 to 80 degrees Fahrenheit. Cover it with a humidity dome, clear plastic bag, or clear plastic storage container to keep the air around the graft at 90 to 95 percent humidity. The goal is to prevent the cut surfaces from drying out while the cambium layers fuse.
Keep the soil moist but not waterlogged. Water from below if possible—set the pot in a tray of water and let it wick up—to avoid splashing the graft union. Do not mist the leaves directly, as this can introduce fungal disease.
After 7 to 10 days, the graft union should begin to callus over (form a white, waxy tissue). At this point, you can gradually increase air circulation by opening the humidity dome for a few hours each day, then leaving it off entirely. The entire healing process usually takes 2 to 3 weeks. Do not remove the clip or tape until the graft is clearly solid and the scion is growing new leaves.
Remove rootstock leaves and grow the plant normally
Once the graft has healed and the scion is producing new growth, remove all leaves from the rootstock below the graft union. These leaves will try to grow and compete with the scion for resources. Pinch them off as they appear over the next few weeks. The goal is to force all the plant's energy into the scion.
Harden off the grafted plant by gradually exposing it to outdoor conditions over 7 to 10 days, just as you would with any seedling. Move it to a sheltered spot outdoors for a few hours, then gradually increase light and air movement. After hardening off, transplant it into the garden or a larger pot and grow it as you would any tomato plant.
The grafted plant will produce fruit identical to the scion variety. The roots, however, remain the disease-resistant rootstock. This is the entire point of grafting: you get the fruit you want and the disease resistance you need.
Troubleshoot common grafting problems
If the graft union turns black or smells rotten, fungal or bacterial rot has invaded the cut. This usually happens if the humidity was too high for too long or if the blade was contaminated. Remove the plant and start over with a fresh graft or a new seedling. Do not compost the failed plant; discard it in the trash.
If the scion wilts and does not recover after 2 weeks, the graft did not take. The cut surfaces may not have made good contact, or the plant may have dried out during healing. Again, start over. Grafting success rates for home growers are typically 70 to 90 percent, so expect some failures.
If the scion grows but very slowly, the graft may have taken but the union is weak. This plant will often catch up once it is in the garden and the roots have access to more nutrients. You can keep it or compost it and try again.
Frequently Asked Questions
Can I graft a tomato scion onto a pepper rootstock or vice versa?
No. Tomatoes and peppers are different species and will not fuse. Grafting only works between plants in the same species or very closely related species. Tomato-to-tomato grafting is reliable; tomato-to-other-crops is not.
What if I cannot find the exact rootstock variety I want?
Many seed companies now sell grafted seedlings ready to plant, which costs $4 to $8 per plant but saves you the work. Alternatively, you can use any disease-resistant tomato variety as a rootstock. The fruit will be different, but the disease resistance will still work.
Do grafted tomatoes produce more fruit than ungrafted ones?
In disease-free soil, grafted and ungrafted plants of the same scion variety produce similar yields. In soil with disease pressure, grafted plants often outyield ungrafted ones because the rootstock keeps them alive and productive longer. The real benefit is growing varieties that would otherwise fail in your soil.
Can I save seeds from a grafted tomato plant?
Yes, but the seeds will grow into plants identical to the scion, not the grafted plant. The graft is not inherited. If you want to grow the same variety next year, save seeds from the fruit. If you want the same disease resistance, you will need to graft again or buy grafted seedlings.
How long does a grafted tomato plant live?
A grafted tomato plant has the same lifespan as any tomato—one season in most climates. In warm regions where tomatoes are perennial, a grafted plant can live multiple years, but home growers typically treat them as annuals and replant each spring.