It is well known that witches' brooms of maples have the shortened and rounded middle lobe, but how common or rare is this in non-brooms? I was looking at some of my Japanese maples today when I noticed a leaf with the short centre lobe on one of them, a seed grown selection approximately 8 or 9 years old. I looked more closely and I saw another leaf with this feature and then another, maybe about 5 or 6 altogether, but the tree is not fully leafed out yet. It was definitely a minority of leaves that showed this characteristic, maybe 1 in 20 of the ones I examined. Are there any non-broom cultivars that act similarly? Or is it even a common characteristic in seedling grown maples? On a related note, whilst looking at a robot translated page of a Japanese website I saw that a cultivar with the short middle lobe was described as having the "crab leaf", which to me seemed very visually descriptive. Is this an accurate translation of how the Japanese describe this leaf form or just a glitch in the computer translation? Either way I would find it both more evocative and easier to refer to "crab leaf" maples than "shortened centre lobe" maples.
MAF, I've noticed the "crab leaf" syndrome on a number of non-dwarf maples. These appear somewhat randomly and in small numbers. My Osakazuki had a whole cluster of them once, and I thought for a moment I might have a witches broom developing. But it was a short-lived phenomenon, and the branch is back to normal. Obviously this is a common mutation among JMs, and when a branch gets "stuck" in "crab leaf" mode, then we have a new broom!
These leaves were seen at random all over the tree from top to bottom, on many different branches. Some leaf mutations on cultivar maples I put down to poor propagation practices and selection of inferior material for cloning, but that cannot be the case in a seed grown plant. I wonder if a virus might also be involved in causing such mutations? I will keep a close eye on the plant over the coming years and see if the crab leaves continue to appear.
