Grafting tomatoes on potatoes – not such a new idea

This year I decided to graft some tomatoes onto potatoes to create what used to be called tomtatoes and are called pomatoes in New Zealand. They have recently been made available in large quantities by Thompson & Morgan as TomTatoes (R) and in the USA are sold as Ketchup ‘n’ Fries (R). You end up with one plant that has tomatoes on top and potatoes at the base.

Having done a bit of reading on the matter there seems to be a lot of baloney on the web about the idea. Most of it, obviously, is about the T&M introduction (thought not written by them) and while I will not take away from T & M the credit for making the idea commercially successful or the research needed to find a perfectly suited pairing of potato variety and tomato or the way to get both plants at a state ready for grafting and the method of successfully combining the two, they did not originate the idea.

About seven years ago, at a press event in London, I asked Tom Sharples of Suttons Seeds, who were the first to really push grafted vegetable plants in general, whether they had plans to sell tomtatoes and he replied that he thought they were more of a novelty than a practical proposition so the answer was no.

Some internet articles report that the idea arose in an African prison where, pushed for space, they adopted the method to get greater crops from a small area.

But I did some tomtatoes when I was in my teens which, I am horrified to realise, was about 40 years ago. And I doubt that I came up with the idea either and I must have read something about it and had a go. I can’t honestly remember how I got on with them. I can remember that at the same time I tried grafting Clianthus dampieri (Swainsona formosa) onto colutea to ease its culture and failed. Maybe the tomtatoes failed too – I just can’t remember. But the idea is not new.

Of course there is no reason why anyone would know about my attempts and this could be a case of ‘parallel evolution’ or different people coming up with the same idea at different times in different places. It is certainly not unlikely that you could graft a tomato onto a potato. We don’t bat an eyelid at the idea of grafting a pear on a quince or a cytisus on a laburnum (+ laburnocytisus)*. The fact that tomatoes have now been moved from their genus of lycopericum to solanum, the same as potatoes, makes it even more likely.

So what is a tomtato, what is the point and how does it work?

Well, first of all, it is not a ****** hybrid. As I looked up all the dreadful news stories about the tomtato, written by people who should, quite frankly, have their fingers cut off to stop them writing any more crap (sorry but this really winds me up), I sit here fuming at all the misinformation. A hybrid is produced from seed, combining the genes of the two parents, in each cell. This plant is simply a potato that has had the top chopped off and a tomato put there instead. The two plant part remain distinct – hence you get potatoes and tomatoes, not some odd mix of the two.

In theory you get two crops off one plant, saving space. Much depends on getting two compatible varieties and making sure they ‘stick together’ well so they are vigorous.

How I did it

So, what did I do? The biggest problem, as Paul Hansord, T&M Director, stated in interviews, is to get the stems of both plants of the same diameter so that the cambium, the actively growing tissue around the outside of the stem, lines up on both plants. Potatoes tend to have hollow stems which makes the job extra tricky. Potato shoots tend to be thick and I assume that micropropagation methods were used commercially to grow the potato plantlets, especially as that would be a way to remove virus diseases and ensure vigour.

I got over the thickness issue by using second generation shoots off the potato seed – rub off the main shoots and wait for a second crop of thin ones. In fact I did not always have shoots of the same diameter but if you line up one side of the shoots then they should ‘take’.

So I grew the potato shoots in pots and then decapitated them. It is vital to use a really sharp blade. Everything must be clean. The blade I used for the photos is not ideal – I used a clean one in reality.

tomtato 1

After lopping off the top I cut a vertical slit in it that will receive the tomato part.

I then prepared the tomato part. This was lopped off a seedling and most of  the leaves removed. The base is then cut in a narrow wedge.

tomtato 2

This has to be carefully pushed in the slit in the potato stem. The problem is to hold it in place until the two unite. I had nothing available that would work so I adapted a method called tube grafting and cut some plastic sleeves, from roll-your-own cigarette filters, into 1-1.5cm lengths. I popped these over the potato base and when I pushed in the tomato part the potato stem was widened and gripped the sleeve and held the graft in place – as long as I was careful. (Note – tobacco is riddled with virus that will affect your tomatoes but the filters on their own do not pose a threat).

tomtato 3

In all, I grafted 15 plants and five failed, either through my clumsiness or the fact that the day after, we had a really hot spell that tested the poor plants. Keep them shaded and moist for a week or so until you can see growth on the tomato – a sign that the graft has taken. I also took off any potato shoots.

tomtato 4

Not very elegant but it worked.

We will have to see how things go from here. I will report back.

 

*Now, the clever among you will have noticed + laburnocytisus above. This IS a graft hybrid. The ‘+’ symbol is part of the name and differentiates a graft hybrid from a sexual hybrid which will have an ‘x’ in front of the name. + Laburnocytisus is an oddity where a cytisus (broom) was grafted onto a labaurnum but things went wrong and the instead of a laburnum stem with broom flowers on it a shoot of cytisus grew through an outer layer of laburnum cells to create a chimaera or a combination of the two plants, rather like your hand in a glove. Typically the flowers combine the yellow and pink colours but sometimes the cytisus breaks through or the laburnum blooms so you can get three colours and leaf types on one plant.

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5 Comments on “Grafting tomatoes on potatoes – not such a new idea”

  1. Maria F.
    April 27, 2015 at 6:25 pm #

    Fascinating! I know grafting is best for getting the best trees that yield the best fruit.

  2. thelonggardenpath
    April 28, 2015 at 8:18 am #

    It sounds like a painstaking, fiddly process – let’s hope it’s worth it! It sounds like a pretty good “take” rate. Should get some good plants!

    • thebikinggardener
      April 29, 2015 at 5:22 pm #

      Thank you. It is a bit hit and miss because I just used the one spud variety but after a slow start they seem ok so far

  3. sueturner31
    April 29, 2015 at 4:34 pm #

    You know we are never too old to learn…fascinating. Thanks.

    • thebikinggardener
      April 29, 2015 at 5:25 pm #

      Indeed – especially in gardening – there are always a few tricks and new plants to try 🙂

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