Wednesday, 18 April 2012

How to graft your own tomatoes for disease resistance

Grafted tomato plants are beginning to become available to the home gardener. A grafted plant will have the roots and lower stem of one plant, with upper stem, leaves and fruit grafted on to it to create one new plant.
The idea behind grafting tomatoes is that the roots and lower stem (called the rootstock) will be from a disease-resistant variety; the top part of the new plant (called the scion) will be from a variety bearing highly flavoursome fruit. You, the grower, gets the best of both worlds: plenty of delicious fruit on a disease-resistant plant. As heritage tomatoes have become more popular, gardeners have also had to accept that heirloom varieties are also more prey to diseases such as tomato blight.
Grafting is a long established practice in the world of fruit trees, where the rootstock chosen will often determine the size of the tree. That’s how you get dwarf apple and pear trees where you don’t need a ladder to reach all the fruit.
It’s becoming more widely practised for other fruit as well, but particularly tomatoes.
The downside is that grafted tomato plants aren’t yet widely available and they are more expensive than ordinary plants. Also, the variety of tomato that you want to grow may not be available in grafted form.
So why not graft your own?
It’s not really difficult and only requires one piece of inexpensive specialist equipment – the grafting clip.You’ll also need a sharp blade – a scalpel is ideal, and a clean work surface. We obtained ours from Heirloom Tomatoes in north Yorkshire - they also sell a wide range of tomato seeds, plants and other tomato-related supplies.

Grafting tools. You will need: 1) your rootstock tomato seedling, which will form the roots of the new plant, 2) the 'scion' tomato seedling, which will be the top, fruiting part of the plant, 3) a very sharp clean knife such as a scalpel, 4) grafting clips and, 5) a pot to put your grafted tomato plant into.

The best time to graft tomatoes is when they are still small, at seedling stage. Seedlings work best because the smaller the cut, the quicker and better it heals. For a commercial nursery, early grafting means the space saved (by making two plants into one) can be used for something else.
So, you have your rootstock on one side, the plants that will be the scions on the other. Keep them separate, you don’t want to mix them up. Varieties such as Maxifort or Aegis are grown specifically to provide rootstocks for grafting. They are vigorous, disease-resistant plants. Don’t grow them for the fruits – they’re pretty much inedible by all accounts and the plant runs riot. I doubt you’ll find Maxifort or Aegis in garden centres – try online (Heirloom Tomatoes are, again, a good starting point).

1. Take the rootstock plant (the blight resistant/bottom half) out of the pot, and remove surplus soil. 
2. Remove – as cleanly as possible, this is why you need a very sharp blade – the baby leaves and the top leaves, leaving as long a stem as possible.
3. Take the scion (the fruiting/top half), and remove the baby leaves and a couple of the lower leaves, leaving just the top growth.
4. On the rootstock, cut a downward notch in the stem. Slice about a third of the way in so that you have a fleshy slice of stem either side of the cut. Make a corresponding  upward cut in the scion.
5. Now fit the two together, so that the protruding scion slice fits into the rootstock cut. 
6. Take a grafting clip and clip the wound together, making sure the cut sides fit together snugly. 
7. Gently put the grafted plant back into the pot, with both rootballs covered. 
8. The grafting clips apply just enough pressure to keep the cut sides pressed together without damage the plant tissues.
Leave the new plant somewhere sheltered, out of direct sunlight, for a 3-4 days until it recovers from what is effectively major surgery.
After 3-4 days, you should see that the graft has taken and you can remove the grafting clip – and reuse it of course.
In the next few days after that you should see signs of new growth on the scion. That means it’s time to complete the graft by separating the scion from its own rootstock.
Cut the bottom off the scion just below the graft, so that the top plant is now being fed only by the rootstock.
The top of your tomato plant is now fully grafted to the rootstock. Keep the grafted plant in its pot for a couple of weeks until you can see really strong top growth. Then pot it on, or plant it out as usual.
You should find you have a vigorous, more disease resistant tomato plant.


You can also see how to graft tomatoes on this excellent video from the University of Vermont. This also shows the same grafting process for aubergines as well as two different ways to graft tomatoes.

To buy your grafting kit go here.


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