Unlike apples, there are no extreme dwarfing plum rootstocks. The smallest rootstock available will produce a 3m tall tree with a 3.5m spread, while the largest will produce a 4m tall tree with a 4m spread. They are thus equivalent to M26 and MM106 apple rootstocks respectively.
What Are Rootstocks?
Rootstocks are varieties, often of the same species, on which the variety you buy is grafted. In this case, grafting involves attaching the wood of one variety to another’s roots. Trees are propagated this way for two reasons. Firstly, trees grown on their own roots will not be the same variety as the parent. This is because seeds within the fruit is a mix of two varieties or in the case of self-fertilised trees the variety’s genes rearranged. Thus, the offspring of a Victoria plum will not be a Victoria plum, but something different. And secondly, by using rootstocks nurseries can produce smaller trees better suited to the average size garden.
Rootstocks don’t just control a tree’s vigour, but also affect its precociousness (time to fruit), disease resistance and hardiness. Rootstocks produce smaller trees than one grown on its own roots, an effect which is known as dwarfing. This is because rootstocks’ roots absorb less water and nutrients from the soil. This may sound like a huge drawback, but it is actually a huge benefit. Such trees put more resources into fruiting at the expense of vegetative growth and fruit earlier in their life. Their branches are at a more manageable height and the fruit is therefore easier to harvest.
The downside to some dwarfing rootstocks is they require permanent staking as their shallow roots are liable to uprooting in strong winds.
Testing Rootstocks
Before any large outlay, it is always worth testing multiple rootstocks as you can never know how well a variety or rootstock will perform in local conditions. Any listed eventual size should always be taken as an estimate. Don’t be surprised if your tree ends up smaller or larger than stated.
Plum Tree Rootstocks A-Z
Note: standard refers to a tree grown on its own roots. Thus a rootstock that produces a tree 30% of standard will produce a tree 70% smaller than if it was grown on its own roots.
Pixy
Pixy will produce a tree 42-53% of standard (about 2.5-3m tall) and is somewhat precocious, producing fruit up to a year earlier than St Julien. Pixy requires staking.
Pixy was developed by East Malling and introduced in the 1970s.
St. Julien A
St. Julien A will produce a tree 64-72% of standard (about 3.5-4m tall) and does not require staking. It is the most widely used rootstock in the UK.
VVA-1
VVA-1 will produce a tree 42-53% of standard (about 2.5-3m tall) and requires staking. Compared to Pixy, the rootstock produces larger fruits and crops at an earlier age. Although launched as a more dwarfing rootstock than Pixy, trials have shown great variability in vigour.
VVA-1 was launched in Russia in 2004.
Wavit
Wavit will produce a tree 53-65% of standard (about 3-3.5m tall) and does not require staking. It is slightly more precocious than St. Julien and is free of suckers.
Rootstock Spacing
Pixy and VVA-1 require 3.5m between trees, while St. Julien and Wavit require 4m.
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Jorge works in the Primrose marketing team. He is an avid reader, although struggles to stick to one topic!
His ideal afternoon would involve a long walk, before settling down for scones.
Jorge is a journeyman gardener with experience in growing crops.