Years ago I heard a story. The story teller's cousin has been growing potatoes and tomatoes each of the last several years. Some years, her cousin reported finding hybrid plants that produce edible potatoes and green tomatoes.
From the story, second-hand as it was, I imagined ripe-red tomatoes on a plant that when pulled up had mature potatoes hanging from the roots. There is usually some truth behind a story like this, but perhaps not what the originally teller or the later hearer initially thought.
The two species (tomato, Solanum lysopersicum; potato, S. tuberosum) are in the same genus, but are distantly related enough that they can't cross to form hybrids. Plants with the important traits of both species can be purchased or made at home, but they are the result of actively grafting separate plants together and wouldn't accidentally form in the garden.
As potatoes are in the same genus as tomatoes, they do produce fruit which is very similar to those of tomatoes. However, instead of being large and colorful, potato fruit are small and generally remain green. Most people who've grown potatoes have never seen the fruit because many commercial varieties rarely flower and even more rarely set fruit. Commercial varieties have been bred to not flower and/or produce fruit because that would take energy wasted that could otherwise be used to grow tubers.
The fruit are generally considered to be poisonous (due to high solanine content) like the other non-tuber parts of the plant. Solanine can usually be detected as a bitter taste, but sensitivity to it varies and people have been sickened or killed by consuming too much of it.
Professional potato breeders have been actively reducing the level of solanine in potatoes for decades. A side-effect of this selection process could be the reduction of solanine in the berries as well as the tubers, but nobody seems to have been researching this possibility.
The story teller's cousin could have been growing a potato variety that coincidentally had extra-low solanine levels in its fruit, or they could have a low sensitivity to solanine. Either way, they probably wouldn't have been able to collect enough fruit from the potato plants to be at risk of being in any real danger from the amount of solanine.
A weekend prior to when I first started writing this post, I gathered a batch of fruit from some Yukon Gold potato plants. I tasted one and found it mildly bitter. My mother in law tasted it and found it terribly bitter. We had sampled a similar amount of the fruit and so our different reactions likely reflect different abilities to taste the solanine.
I wouldn't advise eating the tomato-like berries to be found occasionally on potato plants, but they have other uses.Potatoes are typically grown from seed potatoes (either saved from the previous year or bought anew from tissue-culture labs) and thus are genetic clones that will grow/produce very consistently from year to year. The true potato seeds (TPS), however, are the result of a cross- or self-pollination. The mixing up of the parents' genetics means every plant grown from true seed will be different.
The really interesting thing about growing potatoes from TPS is all the minor variations in the plant that might impact production or how the plants grow. Over a few years one could select a variety perfectly-suited to the peculiar conditions of your garden, rather than hoping that the default clones available in the store will work for you. At least that's the theory, if you've got enough time and space to dedicate to the task.
A few years back I ordered some true potato seed from cultivariable.com to start experimenting with in my garden. Most of the seedlings each year have failed for one reason or another.
From the story, second-hand as it was, I imagined ripe-red tomatoes on a plant that when pulled up had mature potatoes hanging from the roots. There is usually some truth behind a story like this, but perhaps not what the originally teller or the later hearer initially thought.
The two species (tomato, Solanum lysopersicum; potato, S. tuberosum) are in the same genus, but are distantly related enough that they can't cross to form hybrids. Plants with the important traits of both species can be purchased or made at home, but they are the result of actively grafting separate plants together and wouldn't accidentally form in the garden.
The fruit are generally considered to be poisonous (due to high solanine content) like the other non-tuber parts of the plant. Solanine can usually be detected as a bitter taste, but sensitivity to it varies and people have been sickened or killed by consuming too much of it.
Professional potato breeders have been actively reducing the level of solanine in potatoes for decades. A side-effect of this selection process could be the reduction of solanine in the berries as well as the tubers, but nobody seems to have been researching this possibility.
The story teller's cousin could have been growing a potato variety that coincidentally had extra-low solanine levels in its fruit, or they could have a low sensitivity to solanine. Either way, they probably wouldn't have been able to collect enough fruit from the potato plants to be at risk of being in any real danger from the amount of solanine.
A weekend prior to when I first started writing this post, I gathered a batch of fruit from some Yukon Gold potato plants. I tasted one and found it mildly bitter. My mother in law tasted it and found it terribly bitter. We had sampled a similar amount of the fruit and so our different reactions likely reflect different abilities to taste the solanine.
As the only potatoes growing in the patch were Yukon Gold, the seeds in the gathered fruit likely represent the result of a self-pollination. Every plant that grows from TPS is instantly a new variety that can then be cloned by saving the tubers. Over a few years one could grow a significant number of new varieties from any given cross, in time developing an appreciation for the genetics that are found in the parent(s). Yukon Gold is a popular variety and others have already performed exactly this experiment.
A forum discussion about TPS about the likely results of growing seeds from Yukon Gold, written by Tom Wagner, a notable tomato and potato breeder:
I have been testing Yukon Gold OP berries for 25 years or more ever since the experimental clone was first accessed by me. In controlled self pollinated berries, as opposed to OP berries, I get a rather predictable segregation of types each time I grow out seedlings. If you grow out seedlings yourself enjoy the following:Yukon Gold is a tetraploid with a complex parentage, potentially giving it a wide range of possible genetic combinations. That most of those possibilities seem to fall into a distinct set of combinations just means that for those visible traits there isn't that much diversity hiding inside the parent. If you want to play with intensely-colored tubers you would have to look elsewhere.
Yukon Gold was selected from a cross between Norgleam (female) and W5279-4 (a yellow-fleshed diploid hybrid of S. phureja and haploid cv Katahdin). Yukon Gold is a tetraploid because of the unreduced gamete from it pollen parent.
- whites with white flesh
- whites with light yellow flesh
- yellows with light yellow flesh
- yellows with medium yellow flesh
- yellows with deeper yellow flesh
- repeat of above but with either light pink eyes/red eye
- all of the above with templates of size, yield, shape, flavor, etc., differences.
The really interesting thing about growing potatoes from TPS is all the minor variations in the plant that might impact production or how the plants grow. Over a few years one could select a variety perfectly-suited to the peculiar conditions of your garden, rather than hoping that the default clones available in the store will work for you. At least that's the theory, if you've got enough time and space to dedicate to the task.
A few plants didn't produce a single tuber. Most of those that produced tubers got infected with what might have been late-blight (Phytophthora infestans). For my purposes, the specific disease didn't matter. Any with an obvious infection were discarded.
Of those that made it to harvest, some didn't survive winter storage. A very few didn't taste good. One tasted like fresh-mowed grass. (In retrospect, I wish I had kept that one for its prank value alone.) A few that made it through all those steps didn't manage to grow any tubers in the next year.
I did end up with a handful of varieties which seem to grow well enough in my environment, produce tubers that store well, and importantly also taste good. A selection of my varieties can be seen in the photos above. Some even ended up having very nice flowers, though one would never mistake the plants for garden flowers. This year I'm planning to grow a commercial type along side mine, to get a better sense for how well they produce vs the commercial control. Every year in the garden is a new experiment.
References:
- Grafted tomato/potato
- www.territorialseed.com/product/grafted-tomtato-ketchup-n-fries/new_for_spring_2015
- www.youtube.com/watch?v=6V_X77CeTcs
- Solanine
- www.food-info.net/uk/qa/qa-fp95.htm
- www.smithsonianmag.com/arts-culture/horrific-tales-of-potatoes-that-caused-mass-sickness-and-even-death-3162870/?no-ist
- Tom Wagner
- Potato Seeds
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