The humble spotted gum is a world class urban tree. Here's why...

LibertyLizard, 9 months ago

Treevan, what do you think are the best Eucalypts for urban forestry? They have a rather poor reputation here in California due to their propensity for limb drop, but few people can actually distinguish the various species enough to consider the pros and cons of each one. To be honest, I struggle with these as well. The dominant species here is E. camaldulensis though we have others as well.

My ideal tree grows tall, tolerates frost, drought, and wet soil, and has strong branches that won’t fall and crush people’s houses. I’m not sure any of the common Eucalypts I’ve seen locally fit the bill, but I haven’t seen this species around yet. They mention cultivars with stronger branches–can I read more about that somewhere?

Treevan, 9 months ago

Probably none? The problem is that the way we design urban spaces doesn’t lend themselves to large trees and Eucalyptus are stupidly large sometimes. If they had planted TPZ/vegetation strips /exclusion zones underneath then they would be doable.

Your climate is different to mine and probably has Winter rains, E.camaludensis doesn’t occur for us. Out of all the urban Eucs, the Spotted are probably the safest where we are. Their branches are mostly inconsequential, straight bole etc. Bifurcation failures can be a problem but that’s a maintenance issue usually. It seems like Corymbia maculata (we have C.citriodora) will likely grow for you as it is in cultivation in locales similar to what you describe outside of its range. It does die suddenly for us but we have a “live fast, die young” climate.

Our big avenues that I’ve seen are C.citriodora/maculata, Araucaria cunninghamii (Hoop Pine), Flinderia australis, Agathis robusta. These fit the large, straight style with F.australis being a little wider. Beaches have A.heterophylla/A.columnaris (Norfolk Island and Cook Pine). You probably want to speak with a South Australian or Victorian. Greg Moore is in Victoria.

I just went and cut some trees in a local plot and they have E.cloeziana. I took a weird panorama and you can see how ‘safeish’ the form is and it self-prunes (none have ever died or failed in the lot):

https://aussie.zone/pictrs/image/53ec1285-e4ff-498c-91e6-7404f73aa777.jpeg

They mention cultivars with stronger branches–can I read more about that somewhere?

It’s the first I’ve heard of it and I was going to go looking. I was involved with some dwarf Eucalyptus plantings back in the say and not sure where that ended up. Probably a PBR (Plant Breeder’s Rights) somewhere in a fancy nursery. There is an individual with the largest collection of Eucalyptus in Australia, I’ll see if he has any articles up. Problem is, most of it is locked behind FB these days especially when you have a VPN like I do.

LibertyLizard, 9 months ago

Personally I think big trees are worth it even if they can be a bit of a hazard. But that means we need to pick the best ones that aren’t prone to breakage. And in parks there are no buildings to hit, so most things can work there, especially more towards the center. The biggest trees we’ll see around here are redwoods, torrey pines, and eucalyptus, usually blue gum or manna gum. Some big, well irrigated parks have large tulip tree (Liriodendron) as well. Then lots of large but not huge broad leafed trees like oaks, elms, plane trees, etc. Many of those large temperate species are likely imperiled by climate change.

I haven’t seen any spotted gum around here but I wonder if I would recognize them anyway. I’ve seen some lemon-scented gums here and there which are beautiful but don’t seem particularly strong. The nicest one around was broken in half after last winter’s storms. I’m also experimenting with ghost gums but they seem to have issues with Phytophthora. I’m growing one in my back yard so we’ll see how that goes.

I’d like to grow some hoop pine but haven’t got my hands on any yet. The few I’ve seen in CA look good but it’s not a well known species here. Seems like it would thrive with its climate requirements but who knows. Cook and norfolk island pines are somewhat common here but seem to be damaged by the cold periodically. Consequently, they don’t look good and develop multiple trunks which lead to breakage. I’ve heard hoop pine is more cold hardy. Bunya also thrives but the cones are a liability issue. I haven’t seen a good Agathis but I’d be interested in trying. It’s a very cool tree. Not sure it’s drought resistant enough to make it through our summers though. We usually have several months where temperatures can exceed 40C and no rain. I want to try klinki pine too but I have no idea if its hardiness has even been tested. That one will be hard to obtain.

Not familiar with the rest of those but I’ll look into them! I did a quick iNaturalist search but there are no observations for Flindersia or E. cloeziana. I did find one record of Flindersia in San Diego, maybe I’ll look for it next time I’m in that area. You’re up in Queensland, right? I think SW Australia is our closest analog but we’re definitely colder in winter. We might be able to get away with subtropical plants but ideally you want a tree to be able to survive down to about -5C without major damage.

Treevan, 9 months ago

Yeah, I think big trees/Eucs are worth it but what I mean is that the way they are placed into the urban landscape needs improvement. Park plantings as well. The risks should be managed, not only with inspection and tree management but with exclusion zones that not only passively protect people but actively improve the health of the tree.

The 3 species of Spotted are superficially similar, with Lemon Scented and C.maculata sometimes difficult to tell apart. Maybe C.citriodora being the northeastern species, even though it’s naturalised all over, isn’t 100% suited. C.maculata seeds should be easy to import. Possibly invasive though! Hoops wouldn’t be too bad.

Since I am in an area with humid Summers and mild Winters, most of anything I suggest wouldn’t be suitable. Plenty of outliers though, western Queensland too. You probably have Brachychiton populneus there?

LibertyLizard, 9 months ago

Your vision of better tree management sounds great, but having worked with my local municipalities I am skeptical it would be implemented.

Few trees are truly invasive here because of the extreme dryness during summer. But some do naturalize in riparian areas. I’m sure there are some maculatas somewhere in CA so I’ll observe them before introducing any.

We do have B. populneus and they do well here. Strange looking tree. I like the look of some of the other Brachychitons better but they’re rare in my area.

Treevan, 9 months ago

www.dn.com.au/Currency_Creek_Arboretum.html

LibertyLizard, 9 months ago

Ah yes I am familiar with Dean Nicole’s work. His knowledge of Eucalypts is amazing. I know our main Eucalypt expert here in CA (Dr. Matt Ritter) consults with Dean when there is a particularly tricky or unusual tree.

The arboretum might be a little far for me to visit but I’m sure it must be very interesting!

Treevan, 9 months ago

I meant if you wish, he would be the person to find out if improved cultivars exist.

LibertyLizard, 9 months ago

Gotcha, thanks.

randomwords, 9 months ago

What is needed is diversity in tree species in urban environments. Stop the monoculture bullshit that causes every tree in a neighborhood to die when a new disease rolls though.

Treevan, 9 months ago

That’s true but the person that wrote this article definitely knows about that.

What is happening in Australia is that Councils are becoming very risk-averse and planting small trees only, usually within the range of 5-8m high (16-26ft). While he writes about a lot of things, I guess he is trying to make it easy on the general public and Councils to decide that maybe some big trees aren’t all bad and scary. Spotteds are quite iconic so if people are made familiar and comfortable maybe they may get used more in urban settings.