In another post we looked at how apple trees are made, but there’s another, more scientific, layer to the life of apple trees. Welcome to the world of apple tree genetics…
Have you noticed how the cooking apple tress in Our English Orchard, which all happen to be a variety called Bramley’s Seedling, are somewhat bigger than the eating apple trees? There are a few reasons for that and most of them are related to the genetics of the tree.
Bramley’s Seedling are a type of Triploid tree; that means they have three sets of chromosomes instead of the usual two sets of chromosomes in Diploid trees (most apple trees are Diploid). Triploid genetics gives Bramley’s Seedling a few advantages but also creates a special difficulty. The advantages include:
- More vegetative growth than a diploid tree, leading to a larger and more vigorous tree.
- Due to the increased vigour and size of the tree, a triploid tree such as Bramley’s Seedling produces a large crop of sizeable fruit.
- Increased vigour also means that they are more disease resistant and longer lived than diploid trees.
- They are also more adaptable to changing climate and more robust under extreme weather conditions.
So triploid trees tend to be larger, more robust and higher yielding. However, they also have a significant drawback. The problem is that triploid trees produce sterile pollen meaning that if you filled an entire orchard with Brambling’s Seedling trees, they would produce very little fruit since the pollen of each tree cannot pollinate either itself or any other tree. For that reason, triploid trees require other varieties of trees for successful pollination and fruit production; that’s why they are planted on an alternating grid pattern with eating apple trees in Our English Orchard.
The robustness of Bramley’s Seedling (triploid) trees means that they will almost always live longer than the eating apple trees (which are all diploid). A Bramley’s Seedling is capable of living 70 or 80 years or more compared to a diploid (eating apple) tree’s lifespan of maybe 40 or 50 years. This leads to an orchard management issue in older and neglected orchards; as the shorter lived eating apple trees die off, the older triploid trees will produce less and less fruit until the whole orchard becomes essentially lifeless.
For that reason, it is important to protect the diploid (eating apple) trees for as long as possible and to replace them as they die off to retain the vigour of the whole orchard. This is part of the responsibility of managing a heritage orchard.