I've seen a few cultivated specimens here that seemed to be intermediate between the eastern and western species.

That's something I always wondered about. There are a few plicata in arboreta around here, and of course, occidentalis is very common. Personally, I'd enjoy seeing the two get together!

+oM

A few cultivars may be hybrids or assigned to the wrong species.

I would assume (but do not actually know) that people have tried to hybridize many similar plants over the years in the effort to get something marketable. Just look how the trade has gone crazy over "Leyland Cypress" and "Green Giant".

Not sure on that - Leyland Cypress was an accidental hybrid, and while the 'Green Giant' cross was deliberate, it was not made for horticultural use but for forestry (trying to get resistance to the fungal disease Didymascella thujina; T. plicata is fast-growing but susceptible, T. standishii is slow-growing but resistant).

Virtually all the other conifer hybrids that have been deliberately made were done by forestry research organisations, too.

Resin

Resin

The Thuja plaiclata x Thuja standishii hybrid is it faster
than Thuja plicata? are all plants genetically indentical?
also is it the only known hybrid in the genus? I think other
hybrids would be possible as below.

Thuja koraiensis x Thuja occidentalis
Thuja koraiensis x Thuja plicata
Thuja koraiensis x Thuja standishii
Thuja koraiensis x Thuja sutchuensis
Thuja occidentalis x Thuja plicata
Thuja occidentalis x Thuja standishii
Thuja occidentalis x Thuja sutchuensis
Thuja plicata x Thuja sutchuensis
Thuja standishii x Thuja sutchuensis

They would make nice arboretum trees

No, it's slightly slower than T. plicata, at least in N European conditions.

I don't know whether what is commercially available is all one clone or not, but I've got a 1994 book about the work of the Danish National Arboretum which has a photo showing a seedbed with (a minimum of) two rows of hybrid seedlings, maybe at least 15-20 two-year old seedlings, between rows of dead T. plicata seedlings. The caption states (translated from Danish) "Resistance testing in Thuja. West American T. plicata dead of disease, and undamaged hybrids with the resistant Japanese T. standishii. Photo B. Søegaard 1953".

How many of these still exist, and how many have been propagated, you'll need to ask the Danish National Arboretum; they may (or may not!) have the info available.

Resin

I too have wondered whether or not if all of the "Green Giants" are clones. It wouldn't surprise me and I would hate that because of the narrow genetic base. From what I can find Green Giant doesn't even produce seed. Is that true? If so it would make me wonder if its a sterile hybrid. Too bad if it was. I would love to see it back crossed with Thuja plicata in the hope of getting a larger tree. But then does anyone really know how big Green Giants will really get?

The cultivar is a clonal one based on a single plant sent from Denmark. See the USNA web page on 'Green Giant'.

USNA fact sheet says 60' x 12'-20' at maturity.

Ok. Here, mine are already 4' across at 9-10' tall. It was pure speculation on my part.

Dax

Probably a guess on their part also, such depictions always have to be representative anyway as tree response varies so much with site conditions. However, they do have a page up where they give dates and dimensions for a specific known planting - we can at least see what has happened so far in that particular instance. I find their information on the tree by searching "usna green giant".

"From what I can find Green Giant doesn't even produce seed. Is that true?"

Certainly produces cones. Whether the seeds are viable or not I don't know, but I'd not be surprised if they were viable.

"Does anyone really know how big Green Giant's will really get?"

I'd agree with Dax, not the USNA sheet. The UK champion, at the Forestry Commission research centre, is already 23 metres tall. I'd think 35-40 metres is well within the bounds of probability, given suitable locations.

Resin

Pineresin,

I'm looking for that source that mentioned that. I too was surprised. I've never grown this yet and so I'm researching it when I have time. As soon as I find that I will copy & paste the link so you can read it for yourself. I'm not saying its true because as I said before I've never grown this just researching it along with Leyland Cypress.

Thanks,

Kanssouri

The phrase used was "at maturity", not "ultimate height" or "final height". They were also writing from the eastern US and not Britain, where a plant that is half T. plicata might grow bigger faster.

Statistics derived from eastern US performance will also be more useful to someone posting from that region than those based on British plantings.

What caught my eye was that original Danish description. "Disease" is almost an unknown entity among the Thuja. And not that Mike Dirr's words are gospel or anything, but even he begins his description of T. occidentalis as "A healthy tree....." which neatly summarizes everything I've ever seen. I live in the land of the latter species home range and quite simply put, they don't fall prey to fungi, bacterial pathogen, or pretty much anything else. They can easily colonize sites with very high water tables-almost singularly so, in fact-and can also survive on windswept cliffs. I have seen damage during extraordinary drought/winter dessication events, but that's really about it.

One other comment: If one were to travel to, say, Vancouver Island, they would not be thinking in terms of T. plicata needing to somehow grow bigger! They become monstrous out there, in a good way!

+oM

I've seen the Thuja plicatas on Vancouver Island and yes, they are huge.
I have a few large ones also. Here's a tree hugger friend with one.
Mike

http://i75.photobucket.com/albums/i283/Botann/2496008070036511179.jpg

That isn't large of course, as far as the species goes - a small number of old growth examples multiple times that in diameter still exist in the region.

Didn't you remove a Green Giant, Mike?

Dax

Gotta be just about the coolest trees around!

+oM

Speaking of Vancouver Island Big Trees...

http://vancouverislandbigtrees.blogspot.com/p/visit-big-trees.html

"What caught my eye was that original Danish description. 'Disease' is almost an unknown entity among the Thuja"

The disease is Didymascella thujina, which can be very damaging to Thuja plicata seedlings growing densely in nursery beds. It doesn't harm them once they're more than 2 or 3 years old. The hybrid Thuja was an early attempt to develop resistance to this for forestry seedling production, as T. standishii seedlings are resistant, though slower-growing. In modern nurseries, the disease is controlled by spraying with fungicides, so the hybrids are no longer of any interest to foresters.

Resin

"The phrase used was "at maturity", not "ultimate height" or "final
height". They were also writing from the eastern US and not Britain,
where a plant that is half T. plicata might grow bigger faster"

Given that "at maturity" likely means in excess of 500-1000 years, I don't see how they or you can be so sure what its height at maturity is ;-)

From what's been posted here and elsewhere, growth rates for 'Green Giant' are pretty similar in the eastern US and in Britain.

Resin

Well, fungicides are indeed a pretty regular feature of the big seedling nurseries, and who knows, maybe the ones with which I'm familiar (seedling nurserries, that is) would also have that pathogen show up were it not for the preventative sprays. But that notwithstanding, Thuja o. as a wild plant and as a landscape cultivar, is notably absent of disease pressure of any kind, again, here where it's native. BTW, sites favorable for regeneration can feature tight groupings of seedlings which would rival any nursery beds. Where I dig them out for transplant, it's hard to sink a shovel in the ground and only get one. Maybe it's wrong though on my part to conflate the Thuja o. experience with T. plicata. They are however, very nearly the same plant.

Back when I worked at the J. W. Toumey Nursery (USFS) in Watersmeet, Michigan, I know we sprayed Daconil on pretty much everything. I should know-on my first day back after a long absence, I got caught in the spray drift out in the field. Welcome back!

+oM

I'm not sure of anything about the ultimate size of the hybrid, have said for years many such trees are too new to know how big they will eventually become - you're barking up the wrong tree trying to make out that I am saying anything otherwise.

As has been discussed on this forum before rates claimed for 'Green Giant' in the eastern US have sometimes been based on behavior of young plants in greenhouses. The main USNA web page on the tree says it grows 1 ft. per year.

every time it's advertised,they say it grows 3 to 5 ft/yr

I can say green giant grows 3 ft/yr

on deep black soil,,lots of moisture

ron

every time it's advertised,they say it grows 3 to 5 ft/yr

That is the rate it was pointed out on a previous thread was based on some young stock in a greenhouse.

And I can say, in a cold Z4 location, this plant looks remarkably good for a few years and then gets utterly nailed by winter effects! Mine were the pride and joy of the field until last winter. Uh....they didn't look so good after that. Since then, they've grown smaller, but that mostly due to my saw.

+oM

Green Giants don't seem to handle shade as well as the T. plicatas.
Mike

I had them in full, wind-blasted sun, and then a few in a partially shaded and very moist site. The ones in the upland were just cruising along until winter before this one. Likewise, those down in the swamp-right next to big stands of native Thuja o.-had been fine and dandy. They're all gone now, or will be as soon as next time I'm up there with a saw. I learned my lesson. There, in the very heart of T. o.'s native range, was I mucking about with this foreign upstart. And zone-pushing too! Like I say, for a time it looked like it was going to work! What it has done for me is reconfirmed my deep love and respect for the native trees in the "cedar swamp". And what's really neat about those guys-if I dig one, throw it over my shoulder, and drop it in a hole up the hill somewhere, it will not die. Even my deer there appear to be dumb. They evidently don't know they're supposed to decimate this tree. They do less than a half-mile away!

+oM

"But that notwithstanding, Thuja o. as a wild plant and as a landscape
cultivar, is notably absent of disease pressure of any kind, again, here
where it's native"

Don't they get badly damaged by Odocoileus blight?

Resin

Resin, I've evidently got dumb deer on my land. Yes, as a generality, it is said that deer are removing this species from the landscape-in that no regeneration can take place without getting munched. But..........this is highly nuanced, and it would help if you knew the geography-along Wisconsin's "east coast" are several counties with dolomitic limestone very near to the surface. Door County is the most famous, but south of that, the same situation exists. In these counties, "white cedar" is able to regenerate, due to its ubiquity (my theory) in the landscape, such that hungry deer can't eat all of it. And even though often considered a "swamp tree", in these counties it grows up hills, on cliffs, etc.

Now.........here's where it gets hairy: My land (home of the dumb deer) is NOT in that belt-not quite. It lies just north and west of the limestone area, my soil being sandy loam. But the plant is still extremely common, and looks just as good as it does in Door, Kewaunee, Manitowoc, etc. I believe there's some factor by which the limestone is still present-or its influence is. Thuja o. is after all, a well-known calciphile. In any case, it's a real common species in my central Oconto County location. We've counted up to 38 deer at a time in our field. Under the "cedars" in the swamp, there is not one square inch of snow-covered ground not also imprinted with deer prints. It's not as though they're not present. Far from it. But I can drag a sapling out into plain sight in the field, plant it and forget it. It won't get munched, but it will grow, as if nothing ever happened.

Sorry for this treatise. If you lived here, you'd be even more surprised at this set of facts, given it's obvious you have awareness of this issue from afar.

+oM

That is the rate it was pointed out on a previous thread was based on some young stock in a greenhouse.

NO,,,that is the rate I observe in my back yard

I'm telling you they grow 3 ft/yr

ron

Location, location, location!

+oM