Grafted plants appear to be increasingly common, particularly tomatoes, but also peppers, chillies, aubergines, cucumbers, and so on. They offer two potential advantages – vigour and disease resistance. Depending on the sort of rootstock used, a grafted plant may be much more vigorous than a non grafted plant. This vigour may be directed towards increase vegetative growth, which is common amongst the commercial growers who have the height needed to keep the plants growing through an extended season and are likely to be laying down the stems as they grow. Alternatively, more of the energy may be directed towards fruit production and it is this sort, the so-called generative rootstocks, that are likely to be of most value to the amateur gardener. Grafted plants are typically expected to produce a higher yield and may well, in this way, justify their additional costs.
The second potential advantage is disease resistance. Rootstocks are chosen not only for vigour but also for a their resistance to a wide range of soil borne pests and diseases. This can be especially advantageous if growing in greenhouse or polytunnel beds year after year as we do. Over time there can be a build up of problems that are harboured in the soil and unless the soil is swapped out for fresh from time to time, this can result in plants of reduced vigour and poor yield. I suspect that we may be seeing this in our greenhouse beds now so grafting is a potential solution that would allow us to continue to plant in this same soil. I have found many advantages to planting in beds rather than pots, or, worse, growbags. The plants tend to be more robust; there is space and depth of soil into which they can get their roots, and tomatoes are capable of producing impressive root systems if allowed. Planted into deep fertile beds they are potentially more vigorous and more productive. When we moved from pots to beds the difference was remarkable.
Grafted plants may offer some advantages but there are also some drawbacks. They are expensive, often several times the cost of a non grafted plant of the same variety, and far more than those raised at home from seed. The range of varieties available as grafted plants is also rather limited and the majority are modern F1 hybrids. I generally grow few hybrids, preferring open pollinated varieties and, where possible, traditional or heirloom varieties that have some culinary, geographical, cultural, or historical interest. Few of the old varieties can be found as grafted plants. Therefore, if I want to enjoy the potential benefits of grafted plants but with the open pollinated varieties that I prefer, I need to graft my own.
This year, I have gone through the entire process of grafting tomato plants for the first time, experimenting with grafting old open pollinated varieties onto a modern hybrid rootstock. The videos below follow the process from sowing to planting out. I am primarily interested in the disease resistance of the rootstock but, naturally, would be quite pleased to improve yield. Yield is rarely a significant concern for me. I am happy to grow varieties that have relatively poor yield, if the crop itself is well flavoured and the variety is interesting to me. Many of the old tomatoes, especially the larger fruited sorts, produce only a modest crop, and this may be improved by the grafting process, which is a secondary but welcome benefit.