How Do Tomato Grafting Collars Work?

Tomato plant (Lycopersicon esculentum) tube grafting with a tube or collar has been replaced by grafting with a plastic clip. Simple grafting tubes or collars were just large enough to fit over the rootstock, which is the graft's bottom part and provides roots, and the scion, which is the graft's top part and grows branches and tomato fruits. The function of tubes or collars and clips is the same: to hold the two graft parts together long enough for them to grow together.

Tomatoes are grafted to produce disease resistant varieties and to grow more tomato fruits than they would otherwise. In cleft grafting, the end of a scion is cut into a wedge and inserted into a vertical incision on the rootstock; the parts are held together with a plastic clip or parafilm. In side grafting, matching 45-degree angled cuts in the scion and rootstock are held in place with parafilm. In tube or splice grafting, the easiest and most widely used method, a plastic grafting clip holds the scion and rootstock together. Grafting tubes or collars have been largely replaced by specially designed plastic clips.

The best tomato plants for tube grafting are at least 4 inches tall with 1/8-inch-wide stems. Both the rootstock plant and the scion plant should be the same size. Each of them should have two to four cotyledon, which are their first leaves.

Individual peat or paper planting pots filled with a commercial potting mix work well to hold grafted plants. Graft in early morning or early evening, when the rootstock and scion plants lose less water than other times through transpiration, a form of evaporation through pores in their leaves. Make a grafting cut below the cotyledon leaves on the rootstock plant and the scion plant. The cuts can be made straight across, but cutting at a slant allows more of the two cut parts to make contact with each other, helping them grow together. Use a small tube, or collar, or a tomato grafting clip to hold the two cut parts together.

The rootstock and scion need to grow together so vascular tissue can supply the scion with the water and nutrients it needs to grow. The joining process occurs best in an enclosed chamber with a temperature of 70 to 80 degrees Fahrenheit and a relative humidity of 80 to 95 percent. You can fashion one yourself from clear plastic. Do not give a grafted plant direct light or mist it; instead, place the plant's peat or paper pot in a low-light location and in a tray holding shallow water; the water will move upward into the pot through osmosis, a process called wicking. The plant will wilt slightly the first day after its two parts were attached but will recover slowly afterward. After two days of low light, move the plant to bright light. The graft union will heal in three to five days. Leave the grafting clip in place, and eventually it will fall off as the grafted stem grows thicker.