I first came across grafted tomato plants in the seed and plant catalogues a couple of years ago, but completely dismissed them as a bit of a gimmick and rather expensive for most vegetable growing mortals like me at around £9.95 a pop for three plants. Come to think about it, it must be grafted plants I've seen on sale at our local garden centre sometimes. It would explain their rather hefty price tag (around £4.99 for one plant).
Then a couple of weeks ago Geoff wrote over at his GardenForum about how he's going to try them out this year. We got chatting in the comments, as you do:
VP: I'm glad you mentioned grafted vegetables, because I can't get my head around what on earth you graft a tomato or pepper plant onto?
And having shelled out your £9.99 + p&p for 3 plants, do you get sufficient extra crops to justify the expense?And are the tomato grafts just as vulnerable to blight, bearing in mind I've lost my (albeit outdoor crop, not having a greenhouse to hand) to blight 3 years in a row now.
As you can see, I've been giving these quite a bit of thought!
Geoff: Just like fruit, the vegetables are grafted onto rootstocks of the same species/related species that have been bred to provide specific characteristics.
For the vegetables these characteristics include healthier, more robust plants with greater pest & disease resistance (the plants aren't blight resistant as such, but are more vigorous and should grow through the disease), larger yields (up to 15-20%; the rootstocks put more of the plants' energy into fruit production and less into overall growth) produced earlier and later, less susceptibility to nutritional disorders and less susceptible to poor weather/cooler conditions.
Around 60% of all commercial tomato crops are produced on grafted plants, as is most aubergine production and the majority of organic peppers and cucumbers. So, if they're good enough for the professionals - they should be good enough for us!
Hope that helps - and stops the brain ache!
Since then I've researched this technique a bit more. It's used extensively in Asia and there's a lot of information about it coming out of North America. It's not new: our own Allotments4All forum mentions it being popular during the 1960s for greenhouse grown tomatoes, particularly before varieties (like Alicante) suitable for coldhouse growing were available. Another A4A member tells how he's grafted tomatoes onto potato rootstock and vice versa. It seems grafting potatoes onto tomato rootstock is a good way of obtaining lots of potato seed especially when breeding them (note to self: must ask Tater Mater if he's tried this technique).
I haven't found much in the way of grafting being used outdoors (which is what I'm interested in) and I still wonder whether blight years like those we've had lately would still decimate crops. The references I've found talk mainly about soil borne disease prevention, which is only part of the story as far as blight is concerned. Also the varieties available aren't that well known to me - I wonder if they're the ones usually grown commercially? In which case they may not have the characteristics home growers value, such as taste. So I don't think there's much of value to me yet, though I'll be watching the results of Geoff's experiment with interest. He's also keen (as I am too) to hear from anyone who has tried them before or is going to this year, or has tried the grafting technique themselves.
If you'd like to try it out, then this YouTube video gives a detailed account:
Update June 2012: Since writing this post I've also seen how grafted plants are grown commercially. There are also varieties available now which are suitable for growing outdoors.