I promised that I would let everyone know how our grafted tomato experiment turned out so here it is:
As a quick re-cap, I grew two 'Black Pear' tomato plants, one of which was grafted. They were certified organic plants from Ezra's Organics and I planted them on 6/16/12. That's a little later than I normally would plant tomatoes but that was when they delivered the plants to me.
The plants grew in the same raised bed so they had identical soil preparation. I used some John & Bob's soil conditioner per Ezra's co-founder Ron McCabe's instructions. The bed was covered with red plastic mulch, which is something I've used for the past several years because I've had increased production from my tomato plants in the past as a result.
The grafted plant grew taller (about 62" high) than the 46"-tall, non-grafted plant. Both plants had about the same number of branches but the non-grafted 'Black Pear' was pretty wimpy in appearance. It didn't have very many leaves at all, compared to the dense foliage of the grafted plant.
I pruned back both plants a little, also per Ron's instructions, on about the 1st of September to force each plant to ripen their tomatoes by the end of the growing season.
While we did eat a few tomatoes off of the plants during the past 6 weeks or so, I left the majority of the tomatoes on each plant so I could do a comparison of the pounds of tomatoes each plant produced.
The non-grafted tomato yielded 7.8 lbs compared to a yield of 20.8 lbs on the grafted tomato plant! Now that's an impressive difference.
One of the other touted traits of grafted tomatoes is that they are supposed to be more cold-tolerant than non-grafted plants. I'm not sure I agree with that attribute.
When I harvested the tomatoes a few days ago (so I could weigh them), I left 4 tomatoes on each plant so I could see if the grafted plant would continue growing and ripening its crop. Well, it turns out the grafted tomato got frosted before the non-grafted one. It didn't kill the plants outright but they're pretty much toast at this point. And we haven't even had particularly hard frosts yet.
So my conclusion from this little experiment is that the grafted tomato plant was more robust in its growth habits and was nearly 3 times as productive as the non-grafted plant. But the grafted plant was not more cold-hardy than the other plant.
I did like how Ezra's plants are certified organic and certainly would consider growing more grafted plants again next year because the production was terrific.
If you look at the photo above, you will see the non-grafted plant on the left and the grafted one on the right. Notice how robust the grafted plant is. You can click on the photo to see a larger image of it so you can better compare the two plants.