Depends.

Very prone to a number of diseases including apple scab, fireblight, fungal leaf spotting, several species of leaf eating caterpillars. Severity varies from year to year, but by August most sorbus look pretty woeful in most years.

Latin= Sorbus. In England known as a Rowen.

Sorbus aucuparia with reddish orange berries has naturalized here in western Washington state and a bit of a weed. Looks good with Rose of Sharon.

I watched a group of caterpillars this summer travel about in a small group on the tree rather than randomly spaced about the branches. These were not tent caterpillars. They ate almost every leaf on the 7 ft. tall sapling.

Mike

So European rowan might do better than the American species?

Don't know. I live in the Netherlands and European rowan (Sorbus aucuparia) is native here. In most years it looks awful by the end of August (scab and leaf spots). This year they have been fine and I think that is because of the dry weather in June and July.

But, as I wrote in another topic som weeks ago, asian species are even better. Sorbus commixta and sorbus ulleungensis are my favorits. Might be hard to find in the USA though.

It's interesting that S aucuparia looks bad by the end of Summer in NL. they seem to stay looking good here and are used as street trees in some places. I have S vilmorinii which should be gorgeous with fine, ferny foliage and pink fruit but it has never set many berries for me and I'm thinking of cutting it down. There are a load to choose from: species, hybrids and cultivars. Some have long lasting white fruit and look as if they are in blossom in mid winter. Sorbus varieties

When I was on the south coast (of the UK) in Sept. 2010 the Sorbus were gorgeous and I don't remember seeing such leaf issues.

Zanthoxylum simulans:

As close a substitute as can be hoped for in my humid Chesapeake Bay climate, at least until I actually see any cultivar of Sorbus looking healthy around here - with my own eyes. I'm a little skeptical about 'Longwood Sunset' for example, and besides it doesn't seem to be available.

Its leaves were badly eaten by Japanese beetles as you can see, but it doesn't seem to have affected the berry display at all.

And btw, it's been bearing for a few years and I haven't seen a single seedling anywhere.

A volunteer of the weed tree Sorbus 'aucaparia' snuck into this picture I was taking of some Blue China Firs.

The caterpillars stripped it bare this summer and now it has a new set of leaves for the Fall. Good as new!

Mike

Thanks for the replies

Interesting, Mike.
I've tried the Sorbus x crataegus 'Ivan's Belle'. I've about to remove it because it gets too many pathogenic leaf issues here, and besides now that I've seen it fruit, I don't even like the look of them. They are an unappealing muddy purplish-red, and even they get covered in dark fungal spots. (and the taste is nothing to write home about, unless prepared, which I wouldn't have the time for)

But it too can completely defoliate in summer...and then regrow a second set of leaves in September. Something would have to be really special to put up with that trait, though. It looks hideous as it is defoliating in July, then it's bare in August.

I remember my Grandfather's garden in the 50s. He had two of them flanking the front of his yard. They usually had a few caterpillar nests in them, but didn't get stripped bare like mine get now with a different type of caterpillar.

Mike

Mike, those were not caterpillars on Sorbus that you reported, but rather, sawfly larvae. Used to have an S. aucuparia in the front yard and it was a regular occurrence, the arrival of these guys. For a fun party trick, move in close and watch all of the larvae-every last one of them-freeze in place. Great way to make friends and influence people.

+oM

This is why I keep promoting sorbus commixta as a better mountain ash

I like seeing Sorbus-whether the native or the European import-growing out of cracks in limestone bedrock, etc. out in the wild. It's just not a "legacy" tree or anything of the sort. Short-lived, I see it as better to think of it as a colony of volunteers or some such. It's a little like staghorn/smooth sumac to me.....would it make sense to stress out about the demise of a single stem or "bush" of sumac? IO don't think so. While you're (hypothetical person) stressing out about some fungal disease on the leaves or some crazy bit like that, plenty of new stems are popping out of the ground nearby. Note: A former boss actually wondered-to me-what fungicide to use on his sumac patch up north. Politically, I couldn't tell him that I regarded his question as being a sign of mental illness.

+oM

Ps....no, I'm not saying here that I think the various Sorbus are rhizomatous. That's not at all my point. The point is, that any individual stem of either genus is not worth any amount of effort to "save" it.

I would do a lot to save some of my mountain ashes. Maybe shortlived, but at least 50-70 years. That's the better part of a human life.

Those you cite (huggorm) must therefore be more substantial species, at least in terms of persistence in the environment. I'm still not at all sure there's a great deal of legitimate use for fungicides, etc. on what are supposed to be fit and healthy species for a given locale, but if you've got one teetering on the edge of existence-and for whatever reason it is of importance to you-treat away. I said at the outset that I like these things. Just makes no sense-this for the species I'm familiar with-to try and beat something out of them that they don't have, namely, longevity!

+oM

A lot of people are looking for small, pretty trees to plant close to their house or along the road under power lines. The same two or three trees tend to get overplanted for this use. Maybe in some climates Mountain Ash might be a tree to consider putting "in the rotation"? I'm considering planting a few American Mountain Ash close to the road in front of some slower growing trees, mixed in with hawthorn, redbud and crabapple.

As I said, the one I planted experimentally at my parents survived complete neglect. They are for sale cheap from the NH state nursery, and seem to do well in central NH.

What places do these trees do particularly well or bad? Would planting them be a mistake?

Thanks, +om. I knew they didn't look like caterpillars, but for the lack of the correct term I used caterpillars. Sawfly larvae, huh. Good to know.

I don't get in a fuss over them or the tree. :-) Fun to watch though. I'll try waving at them real close next year when they appear and watch em' freeze. lol

Mike

These can be nice trees and I've seen some gorgeous specimens. They remind me of Betula papyrifera in that they are easy to grow if you can replicate their natural environment, but disease prone and short-lived if you can't. They simply don't hold up in warm, humid, and dry conditions. During my recent trip along Lake Superior I saw some beautiful native Mountain Ash (S. Americana) that were spectacularly laden with fruit.

Has anyone tried S. alnifolia? It is supposedly more tolerant than the other commonly used Mountain Ash. I've got one that I planted from a container and it is doing well. It hasn't fruited yet, but has settled in nicely and looks pretty good.

Funny that you mention s. alnifolia. I harvested berries from one this very day. Nice little tree, looking very different from all other sorbus I have seen.

These trees originate from Yamabe National Park, Hokkaido Japan, and was sowed in 1956.

Yes, simple leaf structure is unique for the genus. Someone will probably prove me wrong on that, but it's the only one I know of. Fall color can also be spectacular, but I haven't seen that on mine yet.

Simple leaf structure, are you talking about non-pinnate leaves? Because there are lots of those. All the whitebeams, sorbus aria probably best known. But also sorbus intermedia that is fairly common in the wild where I live.

Yes - there are lots of simple leaved Sorbus. Some are unique to a single location. I live not far from the Avon Gorge which has 8 endemic Sorbus, all whitebeams. Sorbus

Sorbus aria 'Lutescens' is a really beautiful tree if it will grow for you. It is a common choice for municipal plantings here, but none the less stunning for its ubiquity.

Maackia et al, yes, such locales as the shores of the Great Lakes are ideal Sorbus country, especially-it seems to me-if the land is rocky. Cool conditions, relative freedom from drought conditions (I said relative), is all that is needed. Again, I just would not stress out about the longevity of a single stem. Maybe those whitebeams and the Korean version are superior in that respect-I've never grown them-but at least in terms of aucuparia and decora, this is what I've learned.

+om

wisconsitom, would coastal zone 6 be a good location? Trying to suss out what are and aren't good locations...

Ed, I'd generally think so. There are likely parameters I'm not aware of, but Maackia reports seeing them along Lake Superior, and I've seen them in very dissimilar bedrock, but growing within a stone's throw of Lake Michigan, so there's something going on there. Almost all of the Lake Superior basin would be basaltic and granitic rock-perhaps throw in some sandstone-but Lake Michigan is all limestone if any rock is near the surface, as it was where I saw S. decora literally growing in cracks in the rock. Come to think of it, another fairly frequent sighting is of a volunteer seedling growing up in a moist tree crotch. The seeds seem to have a preference for other than mineral soil, yet a high affinity for minerals themselves, as in bedrock. OR, just the bit of organic material that forms in the crotches of some trees.

+oM

floral - thanks for posting about the 8 endemic Sorbus in Avon Gorge. The link refers to them as "apomictic hybrids" - does that mean they're not technically separate species, but should probably be termed "microspecies" or a "species aggregate"?

Photo below (20 May 2015) is one of a handful of S. alnifolia we planted 9 years ago. No significant pest or disease problems so far, but growth has been very slow. Japanese beetle feeding can sometimes be a problem on this species however.

arbordave, that's about as big as my Sorbus alnifolia was, maybe a little bigger. (bought from the last year of trade at Arborvillage as 'Red Bird - seedling') It had just started producing berries. The next year, it got an absolutely massive case of fireblight with over half the crown being "burned" out. I cut it all out, but the next year it happened again. Since I don't want to have to permanently spray it, I had to cut it down. It had never shown even a bit of disease problems before and I'd assumed it was resistant.

Hopefully won't be a problem for you in the airier climate of SE MI.

Many Rosaceae have trouble with the humidity here, when I bought the
house I had to cut down a massive crabapple that was full of fire blight
and probably scab. Knock on wood but Cotoneaster frigidus seems either immune, or to just get small, self-limiting cases of it.