I think that can happen with invasive plants in general. I remember hearing some statistics about either japanese honeysuckle or chinese privet that it wasn't until about 80 years after introduction that it became "invasive". Of course by then the whole system was primed because so much of it had entered the ecosystem (in this case through landscape plantings) and the invasion just exploded.

That's why I always caution people that if a plant shows itself as invasive one place then it is always possible that one day it will become so elsewhere ... even if it is many years later.

Is this a Tree of Heaven (Ailanthus altissima), or something else?

"Its ability to produce an overly abundant amount of seeds, reproduction through roots and a chemical that can prevent or kill other plants near it has made it a species that have many states - including our own - concerned."
http://www.nature.org/ourinitiatives/regions/northamerica/unitedstates/indiana/journeywithnature/tree-of-heaven-1.xml

Here is a link that might be useful: {{gwi:407309}}

yes, that's tree of heaven, blakrab

It's an invasive pest in what they call the "Gold Rush Country" part of California. There was one in this neighborhood when we moved in 14 years ago, now they are all over. A nasty, nasty weed here.

" In California, it is invasive in the Bay Area, the Central Valley, and in foothill counties with a history of gold mining"

Here is a link that might be useful: Source of quote--USFS document

Same here with Paulownia. I've never seen wild ones until this year. I looked down into a ravine yesterday while crossing a bridge, and they were everywhere.

Are they deciduous in California?

Also curious as to how a (Far) Eastern tree made it to California. Were they planted in the West, as they once were in the East (years ago)?

P.S., not a fan of this tree at all, but what an urban survivor!

Yes they are deciduous in Cali. I think they were introduced over a hundred years ago. I know they're all over in some old mining camp. There is a huge colony of them on one of my favorite hikes. There used to be cabins there long ago. I think they were planted then.

I feel your pain Central_Valley - we inherited a small one with our new house last summer - and after reading about it exhaustively, and a meeting with an arborist - we tried 'girdling' it - cutting a strip of bark all the way around 6 inches wide - it was right before it lost its leaves so we had to wait until now to see if it worked. You'll be happy to hear it's leafing out beautifully ha! I've been scared to cut it down because I hear that only makes it more aggressive (like a horror movie!!) So I now need to look for plan B...I've heard you can drill a hole in it and fill it with the strongest Roundup you can find....Anyone have experience?

And re: it's origins, I learned in a class at Theodore Payne it was brought here to California by Chinese immigrants during the gold rush (building the railroads?) - it's native to China, where it's medicinal, folkloric....But grows waaaay faster here in CA than it does there.... thus invasive.

Here is a link that might be useful: Tree of Heaven Wikipedia - Origins

This post was edited by slowjane on Mon, Apr 21, 14 at 13:52

Collaring Ailanthus versus cutting it down outright, I doubt it makes much difference... once its decided the top is no more, you'll have suckers galore...

...unless you try cutting and then pouring all the roundup you can find directly onto the freshly cut stump. Then... maybe...

After reading again about the tree of heaven I went out and crushed a leaf and smelled it - which had a very faint and if anything pleasant smell. Also realized it's leaves are serrated....thinking it's not ToH after all. Posting pictures in a new thread now.....

I think tree of heaven actually are early colonizing trees and they build the soil into a rich loam. I think people are sortof freaking out too much over them. Also they were native to North America before the last ice age. I think they for fill an interesting role in degraded landscapes like cities by cleaning the air of pollution and building the soil. Maybe not always the most beautiful specimen trees but hey they seem to have a niche now. I think they look better than grass monoculture dubbed "lawns".