Friday, July 1, 2011

Grafted Tomatoes: An Experiment

Grafted tomatoes? Grafted fruit trees make sense, of course, because they last for decades. But why go to the trouble of joining a vigorous, disease-resistant rootstock to the delicate stem of a coveted variety in an annual that will be pulled up after a few brief months? In the photo above you can see the join where two different tomato plants, rootstock and scion -- the top part -- have been painstakingly bonded together through a lengthy process which requires highly specialized growing conditions.

This approach might make more sense than seems evident at first. Grafted vegetables of all types are common in Europe and Asia and are in use among commercial growers in this country. There are notable advantages to strong, healthy, high-yielding plants that can adapt to changing weather and produce lots of the tender heirloom veggies we love to eat.

I first learned all these fun facts about grafted tomatoes last summer from Amy Stewart of the seminal, rabble-rousing blog Garden Rant. It was too late in the season to do anything more than scour the internet for additional information and vow to track some down for 2011.

Our particular Sonoma County micro-climate allows for growing good tomatoes. However, our particular backyard has boggy black clay soil which is very fertile but doesn't drain well and harbors disease. Tomatoes seem especially susceptible. Every year our plants are gradually afflicted with thick curled leaves marked with brown spots. The process starts with the bottom leaves and works slowly upward. It never reaches more than a third of the way up, doesn't kill the plant, and we pick plenty of tomatoes, but it's sooooooo discouraging to watch helplessly as it climbs inexorably, leaving dead branches behind. It affects heirlooms most but doesn't spare the hybrids and doesn't seem to be controlled by rotating the beds each year.

So, when the Territorial Seeds catalog arrived earlier this year from Oregon, with -- surprise! -- a page full of tempting grafted varieties, I ordered six plants, admittedly a bit of a splurge, because the grafted seedlings are about twice as much as regular vegetable starts. Like most backyard tomato growers, I lose judgment when rainbow visions of green vines heavy with jewel-toned heirlooms float before my eyes.

Due to this spring's prolonged chilly, wet weather on the West coast, the plants arrived a couple of weeks later than planned and did not look very good when they got here. All of them were spindly with pale stems and curled, pale leaves; a couple had grown too tall for the shipping box and were broken off at the top. Dilemma: should I send them back and call off the experiment? No. Why wait another whole year to make the trial?

Now I'm grateful to myself for the decision to forge blindly ahead.

I planted out four seedlings and gave two away to a good home. The Brandywine and Japanese Black Trifele pictured above went into the ground on May 29.

Here they are today, a month later. Looking good!

Here are Big Beef (on the left) and San Marzano Gigante 3, planted out at the same time. All of the grafted tomatoes are now about two feet tall and thriving. My friend who took in my two leftover seedlings says his little foundlings are doing just fine.

The grafted tomatoes are running behind our other tomatoes planted on May 9, three weeks earlier: two Better Boy hybrids from Garden Crossings mail order nursery in Michigan (the only place we could find our tried and true favorite workhorse tomato), and the can't-do-without organic Sungold (an F1 hybrid) from our local Sonoma County mail order nursery, Natural Gardening. These "control" plants are now about four feet tall with flowers on both varieties and tiny first fruits on the Sungold. They are also showing the first tell-tale signs of leaf thickening and curling, with accompanying brown spots, just a few here and there on lower leaves.

It's a pretty informal, haphazard experiment. Fortunately, others are conducting much more organized trials.

Amy Stewart is back with an account of a sponsored test she is running in her yard. The wholesale nursery Log House Plants sent her a grafted Big Beef and a non-grafted version. They are set up in identical containers, ready for the grow-off.

I will be following her reports with interest, and watching what happens in my own yard.

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