Sáša Woodruff, The Salt at NPR Food (2/12/15)

"It's not just any old tomato or any old potato. It's actually a really good, all-around potato at the base," says Michael Perry with Thomas & Morgan, the company that first developed the plant in the U.K. "Then on the top you've got the potential to have up to 500 super-sweet fruit." Photo: SuperNaturals

Love growing potatoes and tomatoes? This spring, gardeners in the U.S. (and Europe) will be able to get both tuber and fruit from a single plant.

It's even got a catchy name: Ketchup 'n' Fries.

"It's like a science project," says Alice Doyle of SuperNaturals Grafted Vegetables, the company that's licensing the variety for U.S. markets from the U.K. company that developed it. "It's something that is really bizarre, but it's going to be fun [for gardeners] to measure and see how it grows."

This isn't a genetically modified organism but a plant of two different nightshades: the top of a cherry tomato grafted on to a white potato.

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"Tomatoes and potatoes are in the same family and that makes it feasible," says John Bagnasco, also of SuperNaturals.

Grafting, the technique of taking two different plants in the same family and fusing them together, has been around since ancient times. Today, fruit trees, grape vines and roses are still grafted onto well-established rootstocks. (A New York artist is even attempting to graft branches from 40 different kinds of stone fruit onto a single tree, as The Salt reported in August.)

Grafting is advantageous for higher yields and disease resistance. For example, a tree that is genetically resistant to soil diseases might not produce a juicy peach or a perfectly tart apple. So plant breeders can take branches from trees with tastier fruit and graft them onto the hardy rootstocks.

Over the last century, botanists have discovered vegetable or soft-tissue grafting. Grafters will take two separate seedlings — with stems of the same size and shape — and cut them in half. The top of one is then matched with the wound of the bottom. They are fused with a tiny plastic clip and taken into a special greenhouse while they grow into one plant. If the combination is correct, the whole organism should be stronger.

This idea of the tomato-potato twofer isn't actually new either. In the early 1900s, botanist Luther Burkbank successfully grafted a potato top onto a tomato root, creating a viable plant — except that it was, shall we say, fruitless. He even experimented with a tomato-potato hybrid, affectionately named a "pomato." Since then, home gardeners have experimented with these Chimera-esque grafted plants to varying success.

Finding the right partners is tricky at best. You have to find two plants that work well together to produce a balanced harvest of fruit and tubers.

"If you're growing a potato from a seed, as the potato germinates, the stem is much thinner than a tomato when it germinates," says Bagnasco. "You have to start the seeds at separate times and try to get the potatoes' stem up to size."

The plant is an early tomato grafted to a late-producing potato. The two can be harvested throughout the season. Photo: SuperNaturals

After five years of experimenting, SuperNaturals decided to license an already successful variety developed for Thomas & Morgan, a U.K.-based plant company. About 40,000 TomTatoes were sold last year in U.K., says Michael Perry, a product development manager for Thomas & Morgan who worked on TomTato. He says the goal was to make a combination that was more than a novelty plant.

"It's not just any old tomato or any old potato. It's actually a really good, all-around potato at the base," Perry says. "Then on the top you've got the potential to have up to 500 super-sweet fruit."

They also had to find an early tomato and late-producing potato, so the two could be harvested throughout the season. It took 15 years to develop the winning combination.

The TomTato is being released as Ketchup 'N' Fries in the U.S. this spring and the producers say the plant is sparking new interest in gardening. Perry says it wasn't just his usual customers who were interested in this last year in the U.K.

"It was also teenagers and kids — people who wouldn't have been interested before, so it kind of opened it to a wider audience," he says.

SuperNaturals says garden centers across the country will be stocking Ketchup 'N' Fries in spring. It's also available online at Garden America and at the Territorial Seed Company.

Sáša Woodruff is a freelance broadcast producer and reporter, working for local and national outlets including NPR, APM's Marketplace and PBS. She's currently a producer for PRI's To The Point and blogs about food and gardening at Trowel and Fork.

Copyright 2015 NPR.

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