Tomato grafting is a great way for gardeners to grow their favorite tomatoes on rootstock that is resistant to the soil-borne diseases that plague many gardens. When grafting tomatoes, the preferred tomato cultivar (scion) is clipped to a disease-resistant rootstock then left undisturbed. By providing the right conditions, the two vascular systems grow together, producing a plant with desirable fruit and strong, resilient roots.
Good grafting videos abound and are useful, but the range of options can be confusing and intimidating. To help gardeners improve their chances of success, the Durham County, North Carolina, Extension Master Gardeners tested several grafting methods to find the easiest and most successful. Our grafters, who had little or no experience, achieved, on average, a greater than 80 percent survival rate in the tomatoes using the method below.
Many varieties of tomato rootstocks are available online as seed, with varieties that are resistant to bacterial wilt and verticillium being preferred. We recommend grafting young plants with 2 to 3 sets of leaves (one set of seed leaves — the cotyledon— and 2 to 3 sets of true leaves).
Because rootstock varieties often grow slowly, plan to seed your rootstock varieties 7 to 10 days before your scion variety. The goal is to have both scion and rootstock stems the same diameter where they touch inside the grafting clip.
How to Graft a Tomato
Supplies needed are rootstock and scion seedlings, razor blades, grafting clips (1.5 – 2 mm), healing chamber (tray and humidity dome), a spray bottle of water, and rubbing alcohol.
1. Plan to graft towards evening, and out of bright sunlight. Avoid watering your plants for 12 hours prior to grafting.
2. Prepare a dark spot for the healing chamber such as a dark closet or a blanket-covered table. The room should be 72 to 85°F.
3. Organize your supplies: sort grafting clips by size, sterilize your work surface with alcohol, fill a shallow dish with alcohol to store your razor and keep it clean. Get a good task light and a magnifying glass if necessary.
4. Maintain high humidity inside the chamber by adding a one-quarter inch of water to the bottom of the chamber and spraying the inside of the dome.
5. Visually match your scions and rootstock by size. To avoid confusing rootstock and scions, we kept rootstock on the right.
6. Test a grafting clip for a snug fit on a rootstock stem before any cuts are made.
7. Slice the rootstock and scion stems horizontally. Be sure to cut the root stock below the seed leaves (the first two leaves to emerge). Cut the scion at the point on the stem that is closest in size to the diameter of your rootstock cut. Dip your razor in alcohol between each cut.
8. After the slice, place a clip on the rootstock, then slide the scion into the clip. Squeezing the clip to open it may be helpful.
9. Use a bright light and magnifying glass to insure both stems are touching.
10. Gently mist the top of the plant and place it in the chamber immediately. Continue until you are done. Store the chamber in a dark space for at least 48 to 60 hours.
After the third night of healing (approximately 60 hours) open the chamber vents by 50 percent. Close if wilting occurs.
Over the next 5 to 7 days, observe the tomatoes and gradually reduce humidity by propping open the chamber dome and slowly adding light by moving the healing chamber closer to a window or grow light. On about day 14, the tomato graft should be healed and you can prepare plants for the garden as usual.
For additional resources and information click on the Tomato Grafting Project tab on the Durham Master Gardener’s blog at https://durhammastergardeners.com.