Tomato Grafting for Your Greenhouse
I have been growing tomatoes in the greenhouse for 12 years now. I switched to grafted plants after my house “hit the wall.” After four successful years of growing glorious plants laden with fruit, my un-grafted plants topped out at three feet. Fortunately, I had gotten some grafted plants from a friend. Their production was off the hook, and saved the tomato season for me. From that point on, I was convinced.
Most people are familiar with the idea of grafting, but mainly in an orchard setting. Fruit growers have been putting a desirable fruiting variety, or scion, on a desirable rootstock for years and years. In the US, the move toward grafted tomatoes is gaining year after year. It makes a lot of sense, actually. The breeding that goes into a variety is focused on so many things: fruit quality, appearance, flavor, and disease resistance, to name a few. A finished variety is a best fit of all of those characteristics. Breeding for a rootstock like our new Estamino F1 (which I am excited to try for the first time this year) allows the focus to be on disease resistance and vigor of the roots only. That the fruit is small and inedible isn't a problem. The bottom line is you get a plant that is bred to do one thing, and that's growing roots.
The tools are simple: a razor blade and some grafting clips. I use the replaceable razor blades that are double edged and very thin. They are sharper than the single edge, thicker blades for box cutters and similar applications. I cut them in half, making each package go twice as far, and also keeping my hand away from the business edge of the blade. The other piece is the clip to hold the two plants together.
The two common ways to get the two plants together are either a top graft or a side graft. While the top graft is a little faster, my results have been mixed and unpredictable. The first time I tried the top graft, I had a 95% success rate, but the next time I tried it I had a 5% success rate. Not the consistency I was looking for. The method I use now is the side graft. The scion is not completely severed from its roots, and is much more likely to take the graft. Having access to its roots allows the scion to recover from the procedure much quicker. There is very little down time, and the plant can continue its growth from the second or third day post-graft.
When I am getting ready to graft, I try to find a stretch of days that will be cloudy; not that hard in the spring where we are in Vermont. The lack of intense sun makes it easier for the plants to recover. It’s best not to ask the plant to do too much work after the grafting, giving it adequate time to heal.
I always put my rootstock on the left. Typically the leaves are different enough between the root and the scion, but by sticking to my convention, I never have to worry about who is going on top. I cut the top off the root stock; the plant won’t need it, and it's just extra weight on the graft. Next, I trim off some of the lower leaves of the scion plant, leaving just the smaller leaves at the top near the growth center. I try to find a place on the stem where the two plants naturally line up. This reduces the stress on the plants and minimizes the risk that the graft will twist apart.
I hold the razor blade straight up and down, and make a cut at roughly a 70º angle. The cut goes three-quarters of the way thru the stem. I cut the rootstock down and the scion up. It’s important to leave a quarter of the stem; it acts as a hinge to help hold the stem in place, as well as allowing the scion to continue being fed by its own roots. I gently tip the cuts apart and join the two plants together, making sure the cuts are in good contact with each other. Then I clip the graft, and gently place the two plants into a 4" pot with good soil, and I am done.
Some people cut the roots to the scion plant once the graft has taken, but I don’t bother. The strength of the roots from the rootstock overpowers the scion's roots in time.
In a week or so, I start to investigate the graft and carefully remove the clip and look for signs of healing. The stems should appear fused together. While in time the graft is as strong as any part of the plant, I am tender with them when I am checking in on them and when I first plant them onto the greenhouse. It's ok to use a stake to hold the plant in the position that you want, and I have used bamboo skewers in the 4" pot when I have thought the plant needed the extra support.
So…you have this fancy plant, now what? Because the graft has the power to overload the scion, it's important to stress the plant enough that it feels like it needs to ripen fruit. I run all my plants as a "double leader," where I take the first dominant sucker and trellis that as well. This sucker is located under the flower cluster. Having the extra load on the plant makes the power of the rootstock more balanced, and provides an increase in fruit production, which is after all, what it's all about.
It might sound like a lot of work, but it's not. Really. Just a few extra steps. Once you get the hang of it, it goes pretty smoothly, and the results are something that you get to see in one season. That's a good rate of return.
I hope that the upcoming season of 2013 (how can that be?) is one of your best ever.
P.S. Check out our grafting video here!