Tomato Grafting

In recent years I’ve noticed more and more grafted vegetable plants appearing in Garden Centres and on the web. Initially I thought this was an expensive fad, but when I found out that commercial organic growers were using grafted plants I thought it was time for me to try them.

The aim of grafting tomatoes is to combine a vigorous, disease-resistant rootstock with another variety (the scion) that may not have disease resistance but does have tasty fruit. I suffer with soil borne diseases, if I don’t replace my greenhouse soil the follow on crop of tomatoes is spindly, weak and low yielding, so all the more reason to try them.

Ready grafted plants are available in a limited range of varieties, I wanted to grow my preferred tastier types, so that led me to try a DIY approach growing from seed. Also ready grafted plants are quite expensive, another reason to grow them from seed.

The big disadvantage of DIY grafting is the extra time taken to learn and apply the techniques.

I started January 2012 having watched a few videos on YouTube showing the procedure. It is quite fiddly and a fair amount of dexterity is needed, something I was lacking in. As the rootstock seed is relatively expensive I initially practiced using some surplus seeds. Whilst this helped me develop a technique that suited my banana fingers I also learnt a bit about timing and matching up stem sizes.

During March & April I was sowing batches of the actual Arnold F1 rootstock (from Moles Seeds) and different scions and developing my technique.

 

I initially tried growing both rootstock and scion seedlings together in same pot as described at Step 2) here:
http://www.molesseeds.co.uk/flower_and_vegetable_seed_store_uk/zz640_grafting_tomatoes.pdf

This method did not work for me, the tension between the two plants pulled the grafts apart no matter what I tried.

I used a variety of techniques to hold the graft together and different grafting joints (45 deg cuts and wedge/splice). The grafting clips only worked if the rootstock and scion stems matched exactly, otherwise the joint wasn’t gripped tightly and the scion slowly died:




I tried sticky taping the graft but the stems were too easily damaged and the tape didn’t stick.

Eventually I found silicon grafting supports in a GC which worked well for me:


Once the graft is made the plant needs high humidity and reduced light for a few days (otherwise the scion wilts and dies). Poly bags were no good as it’s very difficult to inspect, pulling off the poly bag usually resulted in separating the graft!. Eventually I settled on a couple of big plastic storage boxes to fully enclose the plants, then sprayed twice a day.
The plants don’t grow during this high humidity/low light phase so the graft procedure sets them back by a fortnight. Here’s my ‘Delicious’ variety, with two grafted plants on the left and non-grafted on the right showing difference in size at this stage:


The non-grafted plants had an extra two weeks under grow-lamps, that’s why they looked healthier. In the long run however the grafted plants caught up and overtook the normal plants in terms of size and produced ripe fruit first.

 

PLANTING:
When it comes to planting I found another disadvantage of grafting. Normally I would ‘deep plant’ tomatoes, plunging them into the soil right up to the first truss. This encourages roots to develop on the buried stem and increases the vertical space for extra trusses before the plant hits the roof. You can’t ‘deep’ plant a grafted plant since the splice needs to be above soil level, otherwise the scion will send out is own roots, negating the advantage of the rootstock’s disease resistance and vigour.

In the long run this was not such a problem. When I dug up my tomatoes at the end of the season, the grafted plants had enormous root systems, maybe three times the size of my deep-planted normal plants growing alongside. Regarding the extra height needed to grow the grafted plants, I found I had to change my normal vine training technique anyway, because the grafted plants were much stronger/taller I trained them up and over the greenhouse roof, and ended up with more trusses.

GROWING COMPARISONS:
I grew grafted and non-grafted plants of the same variety side by side, both in the greenhouse and outdoors. In the greenhouse I grew some in the border soil (that had tomatoes grown in it from the previous year) and some in containers with good quality fresh multi-purpose compost.

The biggest difference was noted in the greenhouse border soil, the grafted plants were both stronger and healthier and produced ripened fruit ahead of normal plants of the same varieties.

In the greenhouse container grown plants there was little noticeable difference, the grafted plants ripened slightly earlier.

For outdoor plants I never noticed any difference in growth between grafted and normal. This may have been down to the terrible weather in 2012 and also that Blight wiped out most of my outdoor plants early on.

 

WHAT I LEARNED:

Varieties: ‘Gardeners Delight’ was by far the easiest variety to take being grafted. In contrast the bush (determinate) variety ‘Siberian’ just wilted and died at an early stage and the one plant that did survive only produced a measly handful of ripe fruit.
Timings are critical to get the rootstock and scion to match up. On my small scale I need to stagger the sowing of rootstock over a period of time rather than all planned at once, this will allow for some variations in size & growth rates.


AUBERGINE AS A ROOTSTOCK
I’d read that Aubergines were used as a rootstock for tomatoes in the far-east. Given that a packet of Aubergines seed is very cheap it was worth experimenting. This did not turn out well, although the grafting was straight-forward the scion tomato rapidly outgrew Aubergine rootstock. Here you can see the difference in size of the rootsock and scion (when I made the graft they were identical diameters)




I ended up with stunted non-flowering plants. It’s an experiment I won’t be repeating

 

COSTS:
The rootstock seeds are more expensive than normal seeds, 50 seeds cost £13 ish. Also there is a one-off expense of the grafting clips, these were about £8. Then there is the extra time involved in grafting, this was significant last year but I was learning then. Hopefully it will be easier/quicker this year and won’t take much longer than the normal chores of sowing, pricking out etc. Set against this is the saving of not having to replace the greenhouse border soil. For me that took a couple of hours at least, plus having to find some spare soil to replace it with that hadn’t had tomatoes/potatoes grown in it for 3 years was not straight-forward.

CONCLUSION:
Even though it is a bit fiddly and time consuming, for me tomato grafting is definitely worth doing for greenhouse border soil grown crops. It saves me having to replace the soil and the plants are much more vigorous. Choosing the right variety is important: Gardeners Delight has been great. Grafting is not worth doing for outdoor or container grown plants.

 

I'll be trying them again this year

 

Thanks Joolz. In a month or so the Garden Centres will start stocking them, apart from the big price difference they don't look that different to normal tomato plants, so easy to miss

 

Yes I had considered doing that, in the end I rigged up a support in the g.house roof si I could train them into the apex then down the other side. I thought the plants would object to growing downwards, but they didn't seem to mind.

I guess that not many people buy rootstock seeds in small quantities, maybe that's why they are so expensive?

It's very difficult to choose which rootstock, I can't recall why I picked Arnold but it does look to have a bigger list of pathogen protection. I've got some left over from last year so I'll use these up first.

 

Thanks, I recall looking at their website and their video was useful (although I failed successfully get that splice being demonstrated to actually 'take', it was far too fiddly and I think I was bruising the stems over-handling them). I think as Scrungee pointed out their shipping costs put me off using them.

Yes I tried that and as you can imagine they rooted very quickly and I enough for another grafting batch. It would be possible to save seed costs by starting say just two from seed very early (Jan say), then chopping up the seedlings to root a couple of dozen plants. The downside would be getting the timings right, as I found out the stems sizes really have to match the scions to get a reliable grafting joint.

 

It was a local independant one. I couldn't find any on ebay although Amazon were selling them from Holland I recall.