This rather narrow unlabelled tree at VanDusen Botanical Garden has pinnately compound leaves. I've checked for trees listed in the bed where this tree is, and am not recognizing anything that should be this. The distinctive features seemed to be the smooth bark with lenticels, generally nine sessile toothed leaflets, grooved rachis and the prickles on the underside of the leaflets. I thought maybe an ash, but I'm not seeing any descriptions with those last two characteristics.
The bud (pic 3) looks very ash-like. A close-up of a bud from a stronger-growing shoot (if accessible!) would help. Grooved rachis is OK for at least some ashes (e.g. F. excelsior). No ashes have prickles on the leaves, but could they be galls, rather than true prickles?
The strong branches were well over my head. Here's a close-up of buds from another low branch. I thought they looked like Fraxinus and were the right colour for F. excelsior, which does have serrated leaves, but I was led astray by the other stuff. And a close-up of what felt like prickles. They're mostly on the veins, but not on all the veins. Do galls do the underside of leaves?
Thought it looked short on low easy-to-reach branches! Yep, an ash, but I'd say the bud colour isn't right for F. excelsior, which has blackish buds. The 'prickles' look more like hairs to me. Not with opposite leaves!
My friend who is learning to be a guide at that garden has figured out the plot map better than I have, and has found Fraxinus mandshurica (or mandschurica - there seem to be proponents of each spelling) in the area. That seems like a good match. This drawing shows the grooved rachis, and this document mentions for leaf surface "hispid on the veins beneath", which I looked up - means bristly hairs! Works for me. Thanks.
Mostly I'm seeing alternate, but if "(sub) opposite" will do, there's one on the Flora and Fauna of Liberia website, Z. gilletii.
