Yes, this actually exists, and yes, it's even called Ketchup 'n Fries. A new variety — and the first of its kind to hit the U.S. market — allows you to grow both a fruit and a tuber on a single plant.
Ketchup 'n Fries is exactly what it sounds like: cherry tomatoes above ground, and white potatoes below ground. While it sounds like some bizarre science experiment, the plant is just an ordinary graft and not a product of genetic modification.
Grafting is common in horticulture; the ancient technique involves taking two or more plants from the same family and fusing them together. Most people are familiar with grafted fruit trees, where a single tree may bear several types of apples or stone fruits on the same rootstock. But grafting isn't just for novelty; plants can be grafted to produce higher yields or greater disease resistance, as is often the case with fruits and roses.
Though tomatoes and potatoes sound far removed in the vegetable world, they both belong to the nightshade family, making them compatible candidates for grafting. In vegetable (or soft tissue) grafting, two separate seedlings with stems of the same size and shape are cut in half. The cut on one seedling is then matched to the cut on the other, fused with a tiny clip, and taken to a greenhouse where the seedlings continue to grow into one plant.
Finding the right combination of seedlings is tricky business, especially with a tomato/potato twofer that matures at different rates. The seemingly unlikely duo was first discovered in the early 1900s, when botanist Luther Burbank successfully grafted a potato top onto a tomato root. Though the plant was viable, it produced no fruits or tubers. Since then, countless gardeners have attempted to graft the two vegetables with varying degrees of success.
Thomas & Morgan, the UK plant company behind Ketchup 'n Fries, spent fifteen years developing an early tomato and late-producing potato combo that could be harvested throughout the season. The grafted variety is said to produce over 500 red cherry tomatoes and 4 to 5 pounds of potatoes.
It was released as the TomTato in the UK last year, and has been licensed to SuperNaturals Grafted Vegetables, LLC, for introduction to the U.S. market as Ketchup 'n Fries.