Rowan and foliage reduction with pinnately compound leaved species

Somewhere I heard Ryan talk about foliage reduction on pinnately compound leaved species (multiple leaflets on a central rachis) and how he was experimenting with foliar reduction by reducing the pairs of leaflets on a rachis down to one or two.
I came to my own conclusions that this might work on Sorbus acuparia last year, I’ve had a root over rock that every year grows, gets cut back and doesn’t develop ramification at all (esentially the same poorly developed tree year after year). So last year, after extension, hardening, and pruning back, I reduced the largest compound leaves to 1 pair, the mid sized leaves to 2, and left the small weak leaves alone (essentially evening the foliar mass across the tree, with a total foliar mass reduction of at least 50% I would guess).
The result was more back-budding and increase in ramification than I’ve seen in a decade of experimentation!
What pinnately compound leaved species do readers of this post have in their collection and how do you treat them?


I’ve got a red buckeye (Aesculus pavia) in a nursery can that I’ve been thinking about experimenting with. I’ve also been considering applying this technique to roses.

Last year I did use it successfully on a Wisteria and got great results. That was based on a Michael Hagedorn blog post.

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I have done his type of minimal defoliation on Mountain Ash for years. Backbuds well. Have gotten the leaf length to shorten somewhat. The long secondary extensions are cut off early. Limb die back is a problem.
Unless the observer KNOWS, they only see leafletts on a small bonsi! Larger trees seem more appropriate. I do 12-24".
Unfortunately the vole ate every ash tree down to the roots… now I have 2 yo forests…
I have used this technique on Horse Chestnuts to good success. Trim the three long fingers 3/4 back in an angular spray. The cut ends do not turn brown. The tree doesnt seem to care. After the first spring leaves come out, adout the time the next bud starts to swell–1/6", carefully pluck or cut the bud. It has two new buds JUST below it that will sprout. I have successfully reduced total leaf legnth to about 3 inches. Be carefull, the next summer, the leaves will try torevert to normal size-- somewhere in the 18-24" Fall terminal bud trimming does help. The dorment buds will show up in the spring!
These species have dorment bud capabilities all the way to the base. They will come up from cut root bases

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Does wisteria count? I picked up a couple late last year, so I haven’t had time to experiment with them. Good to know that it worked for you.

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I would think so, the horticultural response is driven by hormones I guess, so even though they are in a completely different family of plants and a different growth habit it should be transferable!

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Really interesting to read this. I have bought a mountain ash clump last autumn. It looked like it had quite a lot of folliage when I bought it and I was surprised with the lack of ramification when the leaves fell. Your approach is pretty much what I had decided to do from various podcasts I have listened to. It is good to here it validated. Have you any before and after photos of the ramification? It would be good to see those, but also any other peoples ash trees.

I’ve got very few photos of this tree, it’s always been a frustration, but I really love Sorbus as a genus, so I’m glad that I can see ways of improving it. I’d like to get a much better piece of material really, but that will have to wait. I made so may mistakes and learnt so much from this ugly tree, and every year the fresh new foliage delights me!

(As an aside, the name Mountain Ash has always seemed problematic for me, Rowan is a beautiful name and genus Sorbus [Rosaceae] is in a different family to the ashes Fraxinus [Oleaceae]… similarly in the UK we use the name Lime for Linden. [Tillia] baffling.)