Grafted vs. Ungrafted Tomato Report

comments (5) October 10th, 2013

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WesternGardener Jodi Torpey, contributor
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The results of my tomato trials may help Harris Seeds decide which varieties to include in its 2014 gardening catalog.Click To Enlarge

The results of my tomato trials may help Harris Seeds decide which varieties to include in its 2014 gardening catalog.

Photo: Jodi Torpey

When I planted my tomato garden in early June, I wasn't sure what kind of tomato season it would be. The winter and early spring lacked any measurable precipitation and the cool night-time temperatures delayed planting by several weeks.

It seemed like perfect timing to conduct a side-by-side trial of grafted and ungrafted tomatoes.

Harris Seeds invited me to participate in another round of home garden trials and the company sent three varieties of tomato plants to grow in my garden. There were grafted and ungrafted San Marzano, Pink Brandywine and Cherokee Purple.

Summary of Results

The San Marzano grafted tomato plant produced more tomatoes than the ungrafted plant.

The Pink Brandywine ungrafted tomato produced more than the grafted plant.

Cherokee Purple was not planted. I decided to forgo the Cherokee Purple for two reasons: this variety typically takes about two weeks longer to ripen than Black Krim and I wanted to try my Black Krim experiment instead. 

  • This experiment was to evaluate how a tomato cutting I'd saved from my 2012 garden would perform next to a plant started from seed in 2013. The Black Krim tomato grown from seed produced twice as many tomatoes as the plant transplanted as the cutting from last season. Other than more tomatoes, there was no difference in the mature plant size, size of tomatoes or tomato flavor.

Here's how the season unfolded:

Right after planting the garden, the weather suddenly turned very hot--as in several days of 100-degree temperatures. This unwelcome development caught all area gardeners off guard. Those unseasonably warm days affected the tomato plants and it took a few days of cooler weather for them to recover. 

There was also a week of non-stop drenching rain to contend with in September. And an early October killing freeze.

In spite of those frustrating weather challenges, the tomato growing continued. 

The first ripe San Marzano tomatoes were ready to pick (on both plants) August 24. By the end of the season, the grafted tomato plant grew 28 more tomatoes than the ungrafted plant. This includes the big basket of green tomatoes that I had to hastily pick when I heard the prediction for overnight freezing temperatures. The grafted plant grew 107 tomatoes; ungrafted 79.

The first ripe Pink Brandywine tomato came from the ungrafted plant on September 1 and it was huge, weighing in at exactly 1 pound. The first grafted Brandywine was ready two days later and weighed 12 ounces. All the Brandywine tomatoes were big.

The ungrafted Pink Brandywine performed better than the grafted plant, producing 11 more tomatoes. The ungrafted plant grew 29 tomatoes; grafted 18. This was by far, the best total Brandywine crop I've grown.

Because of the mixed results in my small trial, I'm uncertain about the return on investment for grafted plants. It seems like it would be worth it to plant smaller, short-season tomatoes for gardeners who struggle against the elements.

What do you think?

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posted in: tomatoes, grafted tomatoes

Comments (5)

Fantyholmer writes: thanks for share and I like this
Posted: 12:45 am on October 26th
WesternGardener writes: Thanks for your sharing your experience with grafted vs. ungrafted tomatoes.

If you'd like to know more about the grafting process, including the advantages of a tougher root stock, I wrote about it for the Denver Post in an article called "Fusing tomato with tomahto produces a sweeter yield:

Posted: 9:47 am on November 1st
reblack writes: My experience was like Jodi's. The San Marzano's did much better with the grafted tomatoes, and the Brandywines did better with the non grafted plants. I also used Morton Hybrid and there was little difference. However the reason I used the grafted tomatoes was to see if they would do better in my garden which suffers from a fungus and kills the tomatoes after the first crop. I believe it is Verticillium wilt, however, other plants that are susceptible to Verticillium like peppers and egg plant are not affected. The plants initially looked much better with the grafted ones vs. un-grafted, but the results were as I mentioned above. If anyone knows of a grafted tomato that is completely resistant to Vericillium please let me know.
Posted: 9:37 am on October 30th
jo_bo writes: It would be interesting to know what the root stock for grafted tomatoes would do for the scion; disease resistance, earlier crop, etc.
Posted: 9:12 am on October 30th
Kiyomi125 writes: We also tested grafted tomatoes just to see how they faired. We tried 2 varieties: San Marzano and Mamatoro. We also grew 8 other varieties in the same bed. We had an unusual gardening season with prolonged cool spring and a cooler and wetter summer than average. So in our NC garden, none of the tomatoes performed particularly well, but neither of the grafted varieties tested did very well, in fact produced fewer tomatoes than the ungrafted ones. We will be returning to the standard ungrafted ones next season.
Posted: 10:40 am on October 28th
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