Most (or maybe all) of what I am posting right now are are spines or prickles, not thorns, but I don't really get it, though every few months I read up yet again on the differences. Anyway, these are not questions, and anyone is welcome to post uncomfortable-looking photos here. I am starting with Robinia pseudoacacia, which we mostly see unarmed, though the Vancouver Trees App notes that "the stipules on some stems of Robinia species eventually harden into spines ...". I am posting an old photo of a branch just to show what we usually see. This tree was cut down last year, and the building in the background was fairly new, having replaced the original church that burned down in a fire; now a highrise rental building has replaced that. But around the corner is a seedling that looks like what I will show in my next example. What really got me into this is the few dozen Robinia pseudoacacia seedlings in Queen Elizabeth Park, in several spots at around 20 meters of the old tree. Another tree that I seldom see armed, but has well-armed young growth is Aralia elata. I have not seen prickles on this adult tree at the West End Community Centre. The adult trees on the property of this condominium building have been removed (first photo), and this fine collection of youngsters is long-gone, but they were very impressive. I have recently posted this Colletia sp. in the Fragrance thread, but it certainly also belongs in in this thread, with its hefty spines (actually thorns). [Edited - I wrote "spines" because I read that somewhere, but I have since wondered why not "thorns", and now I see that "thorns" is correct. See posting #9.] Here is a little pond in Devonian Harbour Park, at Coal Harbour just east of Stanley Park. The planting here is doing a good enough job at keeping people out of the pond. The anchor planting is Gunnera manicata, with prickles on the leaves and petioles. Much of the rest of the perimeter of the pond has been planted with mightily-spined Cirsium vulgare. I have room for my favourite rose: Rosa sericea subsp. omeiensis forma pteracantha, winged thorn rose, with the best prickles ever. Never mind that they are not so attractive in the winter - the Vancouver Parks Board cuts them back and they grow fast enough in the summer that they have to trim them mid-season. This is an old photo, maybe one I haven't posted. I'm not sure. These are from a little over a week ago at VanDusen Botanical Garden - this doesn't look like it gets cut down every year, but I have no idea.
The locust and Aralia growths are likely to be suckers - yes even at that distance. The second rose may be one other than pteracantha.
Thank you - that's impressive. I saw the rose before seeing the label, and thought it looked like that, but I wondered if the leaflets were a little large, although these photos exaggerate the leaf size. The label said f. pteracantha, but it would not be the first wrong label here, including the plant I really went to see, which I decided was mislabeled. What is it that gives you pause?
Leaflets perhaps different, wide gaps between thorns might have some significance - depends on what the rest of the plant looks like, including the flowers. Because there is at least one superficially similar hybrid combination that is represented in North America by at least one named cultivar: pteragonis - Bing images And I think I've been someplace where there was a seemingly nonconforming plant labeled as pteracantha, maybe it was Van Dusen - which I used to visit pretty much yearly.
Thank you. Might it be just Rosa sericea subsp. omeiensis, not the pteracantha form? Here is a Finnish page with fruits shaped like the ones at VanDusen. I'll try to find hips on the ones in my neighbourhood. Kumpula 31.5.2016: Toukokuun valkoiset ruusut | LUOMUS
I think those are more likely to be suckers than seedlings. A Robinia pseudoacacia is a very hard tree to get rid of as I know well from trying to eliminate one in my previous garden. It suckered for years after the tree was felled. If you will indulge me, one of my funniest memories from my old garden was the time I led my father along a path under a R. pseudoacacia, my little, barefoot, 2-year-old son in tow. All of a sudden the baby started to scream and I grabbed him up, certain that he had stepped on an acacia thorn but there were no cuts on his feet; just little triangular bracts that looked a bit like thorns. Once back in the house, I discovered that a wasp had gotten into his diaper . . . not such a funny story for him.
Oh, the only form with the broad, flat wing-like prickles is f. pteracantha. It doesn't mention anything about subsp. omeiensis. I would think a notable feature of R. sericea, which I find hard to believe, is that it has four sepals and four petals. I found quite an interesting page on Rosa hugonis, one of the parents of the pteragonis hybrid: Rosa hugonis - Trees and Shrubs Online Flora of China treatment of that: Rosa hugonis in Flora of China @ efloras.org The difference, if I were to catch the flowers, would be that this has five sepals and five petals. Photos of the hybrid Rosa x pteragonis ‘Cantabrigiensis’ show less contiguous winged prickles, more like the VanDusen one than the others I photographed. It should have 5 to 8 petals. There were no hips on either R. sericea subsp. omeiensis f. pteracantha in my neighbourhood. Here is the one along English Bay. and in Nelson Park. Here is another from VanDusen - it does sort of look like maybe only four sepals.
More on Colletia. Today I found a youngster in a boulevard planting (not a Parks Board planting). As noted in my edited comment above, I originally referred to the hefty spines because that's what I had read, but today I thought the little leaves growing off those things looked just like the thorn drawing on the Thorns, spines, and prickles - Wikipedia page, with the little leaves growing off the thorn. That hefty structure is acting like a modified branch or stem, exactly the Wikipedia definition of a thorn. The Botany Photo of the Day on Colletia hystrix ‘Rosea’ calls them thorns, so I feel like I have learned a teeny bit of the puzzle.
I just posted this elsewhere, but it's useful here as an illustration for thorns on Pyracantha. Since thorns are modified branches, it helps to identify them when you can see leaves growing off them, as in these two photos.
I just posted this Crataegus aff. mollis from UBC Botanical Garden, but it's such a good candidate for this thread. These seem to be thorns, so the common name hawthorn is apt.
A friend grows a hardy, trifoliate citrus called 'Flying Dragon' with formidable thorns. This photo is from Hardy Orange Tree 'Flying Dragon' Poncirus trifoliata 'Flying Dragon’
