So why graft a plant that has only one season? Isn’t that a lot of work for a little pay off? And expensive to boot? Huh?
REALLY, there are reasons for grafting tomatoes – the same reasons we graft other plants. The rootstock is sturdy, disease resistant, stress tolerant, and/or they increase productivity. The grafted part is said to have better qualities than the original rootstock, such as flavor or size.
Tomato grafting has been used in Asia and Europe for some time (since the 1960s) and is currently used in Mediterranean areas, while it is gaining popularity in the US too. There are several reasons the grafted tomatoes are becoming so popular. The rootstock is chosen to help deal with many kinds of abiotic issues including salinity, drought/flood and temperature extremes. The rootstock selection can be effective against many fungus, bacteria, virus, and even nematodes and may help reduce use of soil fumigants.
Research has shown that the increased fruit yield and size may be due to the increased water and nutrient uptake through the grafted rootstock. This increased uptake includes the macronutrients that enhance yields.
There are several grafting methods in use, both for commercial and individual use – Cleft, Approach, Tube (most common for commercial use), and a new method – Micro.
So, why not grafted tomatoes? With the hope of more disease resistance, stress tolerance, and better yields, it is hard not want to try it out. There are no research based studies to tell us that the claims are true for sure here in Colorado at this time, though North Carolina has done some research (see link below). But it may well be worth your own experiment, either trying your hand at grafting or just ordering a grafted tomato from one of the several companies supplying them in the US. They are a pricier than average tomatoes, but maybe worth the fun of trying it for yourself and seeing what all the fuss is about!
The North Carolina Cooperative Extension has a good paper on tomato grafting and the tube technique at: http://www4.ncsu.edu/~clrivard/TubeGraftingTechnique.pdf