An Update on Grafted Tomatoes

A couple of months ago I had the opportunity to see how grafted tomatoes (and other grafted plants) are produced courtesy of Suttons Seeds. As my previous post about them is in my all time top 10, I couldn't resist going along. As you can see it's a mind boggling operation - horticulture on an industrial scale. 

There's millions of plants at various stages of growth in the greenhouses, all growing under their most suitable conditions and the ever watchful sensors of the computers. Conditions vary (light, temperature, watering) from germination through to when the plant is dispatched to customers. I was pleased to hear a biofuel boiler is onsite to generate some of the heating required.

Before I got to see these plants, I had to undertake a fair amount of plant hygiene measures: not handling tomatoes for a couple of days before my visit, plus washing my hands when I first got onsite and also going through disinfection mats so I didn't bring in anything of concern on my shoes. 

Next year, I'll probably have to suit up and wear a fetching cap over my hair as the hygiene measures are set to be increased. Such measures are understandable when producing plants on this scale, especially as they're supplying commercial ventures in the UK and abroad and so cannot afford to be blamed for any crop failures if and when they occur.

Here's the start of the grafting process. Those fingers are lightning fast at picking off the tops of the plants! These trays contain rootstock. Just like for apple grafting (and elsewhere where this technique is used), the angle of the rootstock and plant top stems have to be just right for the graft to take.

Here you can see the plant top being joined with its rootstock and how tiny the plants are when it's done. And yes, that is a moving conveyor belt you can see, so there's several other people waiting down the line out of my camera shot to deal with the rest of the plants speeding past.

And here's a grafted plant ready for potting up. Note the darker colour of the rootstock. That little plastic clip holds the 2 parts in place until the graft has taken. Different rootstocks are used depending on the tomato used on top. Until recently only varieties suitable for greenhouse growing were available.

However, experiments with less vigorous rootstocks mean some varieties suitable for outdoor growing e.g. 'Gardeners' Delight' are now available. Problems such as fruit splitting had to be overcome, showing the original rootstocks being used were too vigorous for the variety being supported. Trials with less vigorous rootstocks eventually led to successful pairings which resulted in good crops of the desired fruit without losing the benefits of the grafting.

Here's a few 'Elegance' ready for sending out. Andy McIndoe from Hilliers mentioned this variety at Bath University Gardening Club when he came to talk earlier in the year. He's had it fruiting into December in his conservatory. Elsewhere on #saladchat, the results reported from growing grafted tomatoes - of unknown variety - have been mixed. 

I've been lucky enough to have some grafted tomatoes to trial this year. I chose 'Lizzano' as it's suitable for outdoor growing and is a bush variety. However, my plants arrived in late March, way before I would be able to plant them out as I don't have a greenhouse.

They've been residing in my kitchen ever since, with the odd foray outside. Whilst this means we're eating home grown tomatoes now (about 6 weeks earlier than usual), I haven't been able to keep on potting them up for them to reach their maximum potential, as I don't have the room. Pollination's also been a bit hit and miss too, so my crop will be just a few handfuls. Therefore my trial hasn't been that successful because of when I received my plants and my keeping the plants indoors owing to the dreadful weather we've been having.

We were introduced to 'Juanita' (see above) during our visit, which came out top in Suttons' taste trials of 70 varieties last year. We were given a small bagful to take home, which NAH and I thoroughly enjoyed with our salad :)

I've since received some of these plants to trial. Their arrival was much better timed and they're now shivering in the garden awaiting better weather. The day after I planted them out I received my first Full Smiths Period warning email from Blightwatch. I despair of ever giving grafted tomatoes a decent trial this year!

NB Suttons have some open days coming up at their site where you'll have the opportunity of taking part in this year's taste trials as well as gaining an insight into what happens at Suttons. Could be worth building into a break down in Devon? The dates for your diary are 10-12th August.

If you're tempted to give grafted plants a go, do bear in mind the soil should not go above the graft union when you plant them out. If you do, the fruiting part of the plant will root and you'll lose the benefit of the stronger rootstock. This is against the usual advice to bury your tomato plants deeply when planting them in their final positions. You may also find this growing guide and video useful.

You can see in the above picture the fruiting part of the plant also had some tiny rootlets when my 'Juanita' plants arrived, so I had to be most careful when potting them up. These rootlets disappeared after a couple of days in the fresh air.