Most stone fruit trees look pretty orderly, even with light pruning; plums, even the most well-cared-for orchards, look a little insane. The trees are definitely more gnarled and seem to grow in all directions at once and straight up at the same time.
Japanese plums, the type most commonly cultivated, do not self-pollinate. There are a few ways to accommodate this. Two or three varieties that will bloom at the same time and will pollinate each other can be planted in alternating rows, sets of alternating rows, or scattered regularly in a checkerboard pattern throughout the orchard.
This orchard demonstrates another solution – pollenizer limbs. Using pollenizer limbs, which are a different variety grafted onto the tree, (with two to three different varieties used throughout the orchard) means the whole orchard can be planted in a single variety of tree. And it makes them look a little mad.
The pollenizer limbs are allowed to grow above the height of the rest of the tree, on the theory that bees, who aid in pollination, may find the higher, more pollen-laden limb first and then make it down to the blooms on the rest of the tree, which won’t yield as much pollen, but the successive visit to the non-self-fruitful blossom may cause pollination to take place. Wind also carries pollen; if it’s high up, the idea is it’ll be carried further before it hits the ground.
So how does that fruit all the way up there get picked? Usually it doesn’t, and it’s knocked off the tree early on in the season so that it doesn’t fall off later and damage another part of the tree or the crop.
If you didn’t know there was a purpose to that limb, you’d probably say who let that happen? They provide a bit of a zany feel to a batch of trees – the ones with the limbs will probably get voted Most Eccentric when Senior Superlatives roll around.