Ketchup and Fries from the Same Plant

Last year, I posted a blog on the pomato or tomtato, a tomato grafted onto a potato plant. (See Two Vegetables in the Space of One?) I wrote it for no particular reason: I just felt like it. I certainly wasn’t planning ahead. But a touch of clairvoyance must be flowing through my veins, since suddenly the pomato is making it big and appearing in countless columns and blogs, not to mention news reports. I’ve even assured that they will be available locally this spring in ordinary garden centers just about everywhere in North America. The evocative name of Ketchup ‘n’ Fries™ pretty much says it all: grow your own ketchup and fries on the same plant. The same variety, by the way, has already been on sale in Europe for 2 or 3 years under the name of Ketchup ‘n’ Chips ™, a bow to British usage.

Not Such a New Idea

The idea of grafting a tomato plant onto a potato is in fact nothing new. Luther Burbank was doing it back in the early 1900s. A French gardener named Fourquet from Fromont, Seine-et-Marne, is said to have done the same in 1820.

The fact that this is possible at all is because the two plants are closely related, both being in the Solanaceae family. In actual fact, they are now even in the same genus, although that’s a recent change. The tomato is now called Solanum lycopersicum while the potato still has its long-standing botanical name, S. tuberosum. In fact, you can also graft tomatoes onto other related plants, such as eggplants (S. melonogena), tobacco plants (Nicotiana tabacum), and even pepper plants (Capsicum annuum). The latter two may not be solanums, but they are in the right family, the Solanaceae, and apparently that’s close enough.

I actually tried my hand at grafting tomato plants onto potatoes as a biology project way back in high school, nearly 50 years ago. It turned out to be fairly difficult (it wasn’t easy coordinating the growth of the two plants so that both had a similar stem thickness at grafting time, a sine qua non condition for a successful graft) and even when the two did match, I was unable to get all the grafts to take. The two plants that I ended up with did not give conclusive results: the potatoes matured before the tomatoes were ready to harvest, then started to die back, as potatoes do, bringing my experiment to an early conclusion. I ended up with a reasonable harvest of potato tubers, but only 5 small green tomatoes… and remember, that was the total from two plants. I think you could call that a fairly dismal failure!

A Better Choice of Plant Stock

The plants used in producing Ketchup ‘n’ Fries pomatoes are not just any potato and tomato combination, but were carefully studied. I met John Bagnasco of SuperNaturals, the plant’s main supplier in North America, last year at the Garden Writers Association annual show and expo and he explained to me that it took 15 years of experimentation to arrive at two plants that really worked well together. Part of the secret is that the chosen potato is a late variety while the tomato is an early variety: that means the tomatoes will ripen while the potato is still growing, before it starts to go dormant. (Why didn’t I think of that when I did my high school experiment!)

I also tried to find out which cultivars were used (maybe it’s just me, but I like putting the right name on the right plant), but it seems I won’t get my way this time. The names of the two varieties are a “trade secret”. So I’ll just have to accept Ketchup ‘n’ Fries ™ as the grafted plant’s name. All I know about the plants’ real identity is what the press releases say: that the potato is a white-fleshed late one while the tomato is an early red cherry type.

Not Frankstein Plants

GMO activists needn’t jump into action over this: a tomato grafted onto a potato has nothing to do with gene transfers. Grafting has a long and illustrious history in horticulture. Essentially all of the apples produced worldwide come from grafted trees. Of course, it’s true that it’s a case of grafting one kind of apple on another, not on a totally different species, so maybe you feel that example doesn’t count. Consider then the ever-popular orange (C. x sinensis): most of those grown in Florida are grafted onto the roots of a tree that is not an orange tree or even a Citrus, although it is related to the orange: Poncirus trifoliata. So if you eat oranges, you’ve probably been consuming fruits borne on an intergeneric graft (a graft between two different genera) for many years.

The Good and the Bad

But why grow pomatoes rather than tomatoes and potatoes on separate plants in the first place?

Vendors will point out that this helps save space: you’ll get two crops in the same space. Pomatoes can be grown either in the ground or in pots on a balcony, terrace or roof, in rich, moist, well-drained soil in full sun: exactly what the two parents need. For urban gardeners, whose gardening space is very limited, a two-in-one plant makes sense. Also, the potato used is resistant to late blight, a disease that has been wreaking havoc on home-grown tomatoes for the last few years, so you will likely gain disease resistance as well. And according to the suppliers, you can harvest up to 500 cherry tomatoes and 2 kg of potatoes per plant and that seems pretty impressive.

I have to add the main reason for trying these pomatoes might actually be for the sheer pleasure of experimenting. After all, what is gardening if not a long series of experiments? People who want perfect vegetables every time buy them at the supermarket. Only gardeners insist on cultivating vegetables year after year despite results that can be (let’s be honest here!) rather variable!

The downside? The price! I’ve been told these plants will be retailing at $20 to $25 in Canada (I’ve seen $19.95 in the US and £9.99 in Britain) and this is for a small plant. For twenty bucks, I could grow two entire rows of tomatoes and two more rows of potatoes in my veggie garden. So Ketchup ‘n’ Fries pomatoes just aren’t going to be your very best financial decision.

But I’m not saying that I won’t be buying at least one plant, just to see. What can I say? Maybe curiosity killed the cat… but I really do like experimenting!