Very regionally dependant!

In North America, a Thuja purchased in across Canada, the mid-west US, and the eastern US is almost certainly derived from Thuja occidentalis.

Along the west coast (Canada & US)...Thuja plicata

In the southeast & southern states, probably the Thuja 'Green Giant' or similar (Thuja standishii x plicata).

In Europe, I expect Thuja plicata or occidentalis would be the two most likely species (rather than the Asian Thuja). Thuja occidentalis is more versatile (big cultivar selection) so I expect that's the more 'common' one.

By far the dominant one here is T. occidentalis 'Smaragd', from Denmark. It is one of the most prevalent nursery items.

Yup. Thuja occidentalis was the first N. American plant species taken back to Europe for horticultural purposes. This was hundreds of years ago. As such, and given this species genetic plasticity, there have been a great many selections/introductions over that timespan. I think bb's got it right that "Emerald Green", aka Smaragd" has become preeminent in the marketplace.

This is an alright, all-around plant for many uses. I don't care for it however due to its having multiple leaders. It is not the worst offender in that sense, but it can and occasionally does split open under heavy snow or ice load. If one must have a cultivar, I much prefer "Hetz Wintergreen" which is almost always single-leadered.

I'm a huge fan of the native stands of T. occidentalis, such as can be found where I live and all around the Great Lakes region. Contrary to what many seem to think, this tree is usually single-leadered also. They handle enormous snow loads in stride. I've seen young and even not so young plants in my woods bent to the ground, only to spring back to vertical perfection once the snow melts or is blown off.

What height/width/etc. are you after? We can guide you in based on those criteria.

+om

Emerald, Emerald Green etc. are translations of the cultivar name into English - the cultivar is always 'Smaragd', regardless of what language is being spoken.

Hmm, thanks, people. So, according to an Italian on-line nursery that does offer Smaragd,I can expect my plants to grow quickly to 5-6 meters in height, and 1-2 meters wide. Now I think I'll lookaround Internet to see if any italian nurseries offer a simple species thuja, just in case. If not, I'll work on the assumption that the ones I have are indeed Smaragd...cheers, bart

O dear! the same Italian site also offers thuja Plicata Atrovirens,which in contrast can grow up to 12-15 meters high and 4-6 wide! Looking at pictures on Internet, I can't really tell much difference between leaves of the two types, either. Thing is , I was thinking to group them with a cypress sempervirens, having the cypress in the midst of shorter, fatter thujas,but I'd only get the desired effect if these ones I have are indeed Smaragds. Any idea how to tell the two apart?

I've always considered the foliage on T. plicata a bit more coarse, and a bit larger overall. Indeed, some taxonomists consider these two species to be one and the same, merely geographic variants of each other. I'm not saying that, just reporting something I've read.

I strongly doubt you'll find straight species Thujas of any species. I do actually specify straight species T. occidentalis for some of the native restoration work we do, but finding them on the market is a challenge, let alone in Italy.

+oM

I'm going to have to go on-line and look at pictures some more. You are being very helpful however. By now I feel I've narrowed down the possibilities to just the two: the tall growing T.plicata and the smaller Smaragd. Of the three baby shrubs I have, though, I observe that one has a marked pointy cypress-type shape,whereas the other two are more oval/rounded (not ball-shaped at all though). The quest goes on! bart

I have seen beautiful tall Thuja plicata in Washington state. I have no idea what the small trees look like, they were probably all around me but I wasn't paying attention. Maybe the species Thuja aren't available but are there any cultivars that get that tall, bare trunk look at a relatively young age?

>are there any cultivars that get that tall, bare trunk look at a relatively young age?Only under poor conditions.

Any Eastern grown material looking coarser than T. occidentalis I would expect to not actually be T. plicata. The 'Green Giant' hybrid for instance.

Look at 'Hetz' or 'Hetz Wintergreen'-same plant IK believe. It might be the one for you. It does tend to be single-trunked, which I believe to be a huge advantage, leastways where it snows or ice storms occur.

+oM