Grafting Tomatoes

Why Graft A Tomato Plant?

If you prefer the taste of heirloom tomatoes, you know there's no going back to most of the disease-resistant hybrids. But those hybrids grow so nicely. So take advantage of that! Use them as the rootstock.

List of Materials

Heirloom tomato plant
Disease-resistant tomato plant
Gallon pot
Potting soil
4 stakes: These will protect the tomato from the plastic bag, so they should be about 6" taller than the grafted plant
Clear plastic bag: This will cover the grafted plant and part of the gallon pot. It should be at least 6" taller than the plant, and wide enough to surround the plant without bending the leaves, as well as to go over the pot.
Razor blade or grafting knife
Rubber band large enough to go around gallon pot without effort
2 rubber bands or equivalent, very soft, 6" long: These will be used to tie the graft union together, so they must be so soft that they can hold the pieces together without bruising the stems. Cut the rubber bands once to unloop them.
4 wire plant ties at least 6" long.

Choosing Which Plants To Use

Select a healthy heirloom at least 6" tall. You will cut it so you have about 4" of stem on the cutting.

Choose a disease-resistant variety that grows really well in your site. Select a tall, robust plant. At a height of at least 6", preferably more, the rootstock plant's stem should be the same diameter as that of your heirloom's join point.

Note: I grow only indeterminate tomatoes, and I've always used indeterminate plants for rootstocks. I have not tried using cherry tomatoes. I'd like to hear about results using other kinds.

Key Ideas

You want to put an heirloom cutting with about 4" of stem onto a disease-resistant rootstock, and you want the graft union to be high enough so that there's rootstock stem to bury afterward. You want the diameters of the two stems to be the same at the graft union. (This is where the two pieces are joined.)

The two grafted pieces must be gently but firmly touching at all times. The two pieces must not move, dry out, or get cold. The pieces must start off in optimal condition.

When you plant the grafted tomato, no part of the heirloom should touch the soil or mulch.

How To Go About It

Soak both plants for an hour.
Repot the rootstock in the gallon pot. Do not bury any of the stem.
Note the diameter of your heirloom at its join point, where you'll cut it. Find the matching diameter on your rootstock.
At the leaf node just above the rootstock's join point, chop off the top of the plant.
With the razor blade or knife, cut the top of the rootstock's stem into a V shape. Begin the downward cut from the side of the stem. Make the cuts meet cleanly in the middle of the stem. The angle of the two cuts should be around 20 degrees.
With the razor blade or knife, cut the heirloom's stem so that it exactly fills the space in the rootstock's stem.
Position a stake so that the two pieces are perfectly aligned. Fit the two pieces together, and tie them to the stake.
Wrap a soft rubber band very gently around the join and tie it. Use two if necessary.
Poke three stakes into the outer edge of the gallon pot so that they prevent the plastic bag from bending the plant's leaves.
Water the plant.
Put the plastic bag over the stakes and plant. Fasten it onto the gallon pot with the big rubber band, by moving the rubber band up from the bottom of the pot.
Put the plant in indirect light, where it's at least 65 degrees, and there is no wind. Keep it there until you see new growth from the top. Do not let the soil dry out.
Do not allow any growth from below the graft union.
When the grafted plant is growing, gradually remove the plastic bag over several days. Begin by unfastening the bottom of the bag and leaving a space between it and the pot. If the top shows signs of wilting, put the bag back.
Remove the rubber band when the graft is established. The tops of the rootstock will tend to splay apart if given the chance, so be sure there's new tissue in the gap.
Gradually acclimate the grafted plant to full sun, over a few days.
When the graft is strong and acclimated, plant it out. Do not allow any part of the heirloom to touch soil or mulch.