When Tomatoes Grow on a Potato Plant

Potato fruits

By Larry Hodgson

Question: I was amazed to see that my potato plants have produced little green tomatoes. A lot of them even! How could this even be possible?

G. Assad

Answer: Actually, the fruits (they can be green or purple), about the size and shape of a cherry tomato, are not tomatoes, but instead true potato fruits. The tomato (Solanum lycopersicum) and the potato (S. tuberosum) are close relatives, both belonging to the Solanaceae family. So, it’s not all that surprising that their fruits look much alike.

What is so surprisingly to most gardeners is that they see potato fruits so rarely. Many people have grown potatoes their entire life and have only seen fruit a few times. That’s because potato plants usually don’t produce fruits … at least, not under standard garden conditions. And there are several reasons why not.

potato flowers
Potato flowers are not seen on all potato plants. Many varieties rarely if ever bloom. Photo: Steinsplitter, Wikimedia Commons
  • First, some potato varieties rarely flower, especially in northern regions, and if there are no flowers, there will obviously never be any fruit.
  • Also, many of the potato varieties that do flower produce blooms that are male sterile. Their flowers produce either no pollen or the pollen produced isn’t fertile. So, unless a bumblebee carries fertile pollen from a nearby fertile variety of potato plant to the male sterile variety’s blooms, there still won’t be any fruit.
  • Finally, even a male fertile variety that does flower annually may not produce fruit every year. Growing conditions have to be nearly spot on for the fruit to form. Usually this happens when the summer is cool and humid, as this replicates of the conditions of the Andean highlands where the wild potato originated.

Fruits Poisonous but Still Useful

It’s important not to eat the “false tomatoes” that grow on potato plants, as they’re poisonous! In fact, all parts of the potato are poisonous except the tuber.

Potato fruit cut open, showing seeds
You can harvest and sow the seeds found in potato fruits. Photo: Rasbak, Wikimedia Commons

On the other hand, you can put the fruits to good use. When your plant produces fruits, simply let them ripen on the plant (the fruit changes color or softens when ripe), then harvest, dry and store the seeds. Then, next spring, sow the seeds indoors (exactly as you would sow tomato seeds) in order to produce potato plants for the coming season.

Transplanted to the garden, the potato seedlings you produce will grow into potato plants that will, in late summer, produce tubers … edible ones, of course. On the other hand, the color of the skin and the flesh, the shape, the size and the quality of the tubers can vary, because cultivated potatoes are of hybrid origin and don’t come true to type from seed (the seeds don’t produce plants identical to those of the mother plant). So, you never know what the tubers will be like until you harvest them! 

Potato fruits: they may look like green tomatoes, but they aren’t. And they’re poisonous. So, no fried green tomatoes with these fruits!

Larry Hodgson is one of Canada’s best-known garden communicators. He has notably been editor-in-chief of HousePlant Magazine, Fleurs, Plantes et Jardins, À Fleur de Pot and Houseplant Forum magazines and is currently the garden correspondent for Le Soleil and radio garden commentator for CKIA-FM Radio. He has written for many garden publications in both the United States and Canada, including Canadian Gardening, Harrowsmith, Horticulture, Fine Gardening and Organic Gardening. He also speaks frequently to horticultural groups throughout Canada and the U.S. His book credits include The Garden Lover’s Guide to Canada, Complete Guide to Houseplants, Making the Most of Shade, Perennials for Every Purpose, Annuals for Every Purpose, and Houseplants for Dummies, as well as nearly 60 other titles in English and French. He is a past president of the Garden Writers Association (now Garden Communicators International) and the winner of the prestigious 2006 Garden Media Promoter Award offered by the Perennial Plant Association. He resides in Quebec City, Quebec, Canada.

7 comments on “When Tomatoes Grow on a Potato Plant

  1. WOW! I knew the tomato,potato, eggplant & pepper plant are in the same family with Bella donna, but never had potato fruit in the 40 years of growing potatoes.
    Learn something new everyday. Thanks.

  2. Do you remember the ‘tomtato’ and the ‘Kutchup & Fries’ grafted tomato and potato plants? Those were both lame and expensive. I would rather select good varieties of tomatoes and good varieties of potatoes, rather than take whatever happened to be compatible for grafting.

  3. John Wilson

    I planted out 12 seed potatoes (tubers) in terra cotta plastic pots this spring, and about half of them produced these fruits following flowering. This was only the second time I have grown potatoes, but the first time I have let the flowers mature (last year I removed the flowers after blooming). They were grown quite close to two different varieties of tomatoes (1 cherry, and 1 slicer), so I wonder if this might have contributed to the formation of the potato “fruit”? Interesting article…

  4. Viv Potter

    Three years ago one of our store bought potato plants grew the “cherry tomatoe ball”. So I researched, followed advice and today unearthed 202 grams of a bran new potaoes. I kept one potatoe to grow this clone next year. It has been a treat and so much fun growing a new and unique (genetic ) plant – a plant that has never been seen before and unless i plant the resulting tubers will never be seen again. What a joy! I think all gardeners should give it a go especially if you were fortunate enough to be gifted the potato seed ball. Wish i could attach a picture. There’s three more plants but not ready to dig up and don’t seem to be flowering- way too hot this year.

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