biodiverseed:

When the Rootstock Sprouts with a Vengeance

I saw this tree beside a local apartment building today: it’s probably been planted by the municipality or the tenant’s association, and has perhaps not been tended so carefully since then.

I am guessing the tree is meant to display as a double-flowering pink ornamental cherry, but the single white blossoms are likely from the rootstock, which has formed a shoot parallel to the grafted scion shoot, and grown more vigorously.

The result is a tree with two distinct genetic expressions: the upright form and white blossoms of the rootstock tower over the drooping form and pink blossoms of the scion.

In the long term, without pruning out the more vigorous rootstock trunks, the white-flowering parts of the tree will shade or crowd out the pink-flowering grafted parts, affecting them to make up an increasingly small percentage of the tree’s bulk.

Many ornamental grafted trees are selected for their special flowering characteristics (in this case, large, double, pink blossoms), and not for their vigour. They are grafted to a rootstock that does well in the immediate climate, and has characteristics like disease-resistance. Many rootstocks produce ‘suckers’ (basal shoots), which are normally controlled through pruning.

I love multi-grafted trees, however, so I find this arrangement rather charming. It does, however, provide an illustration of why pruning grafted trees – especially between cultivars that have varying shapes, colours, and vigour – is important.

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More Prunus trees and grafting here