Fraxinus

About five years ago a chap from the RHS identified a seedling on the edge of our back hedge as a fraxinus excelsior f. diversifolia. This was noticed at reference 1. Later that year, I cut it down by accident, but was pleased to be able to report the following year at reference 2 that it had sprouted from the stump.

However, while it is still there, and now carefully protected, it has never really recovered, and has yet to make the size it had back in 2015. As can be seen in the snap left, with the lead bud not long burst. There are some more buds further down.

Maybe, by the end of this year, it will have attained its former size.

Meanwhile, some confusion on the taxonomy front. What does the 'f.' bit in the name do? Why are the leaves at reference 3 pointed, rather than the round of my seedling? Is it one of those trees on which the shape of the leaves depends on circumstances; the amount of light, the age of the tree and so on. It is certainly the case that ivy leaves vary considerably in size and shape from place to place, from plant to plant.

Reference 1: https://psmv3.blogspot.com/2016/06/fraxinus-excelsior.html.

Reference 2: http://psmv2.blogspot.com/2015/07/not-exotic.html.

Reference 3: https://www.vdberk.co.uk/trees/fraxinus-excelsior-diversifolia/.