Australian natives for the gulf coast

[thyerr01]

Nowhere in Australia experiences the combination of hot humid summers and winters with periodic severe freezes we get in the gulf coast and southeast, making it a rough climate for growing most Australian plants. Callistemons are some of the most tolerant Aus natives and there are several different species/hybrids commonly grown in Texas, many of which survived Palmageddon. I occasionally saw Eucalypts in Houston before the freeze and at least a few survived (out near IAH). I have also surprisingly seen both hybrid and species (A. flavidus) kangaroo paws for sale at the big box hardware stores, and more recently a few hybrid Grevilleas at some of the specialty nurseries. Another forum member from the southeast reported good survival of G. 'peaches and cream' at 22F this last winter.

I put several things in raised beds in October last year including Corymbia ptychocarpa, Kunzea baxteri, Callistemon phoeniceus/montana/pinifolius/glauca and some Grevillea victorieae cultivars and hybrids. All survived our mostly mild winter in Houston, although the C. ptychocarpa lost most of their leaves and are resprouting from the stem and lignotubers. I have several more Eucalypts and Melaleucas to start from seed, and I'll probably roll the dice on the A. flavidus kangaroo paws if I see them again.

I am curious if anyone in the gulf/southeast is having success with anything different or especially unusual, maybe Correa hybrids or East Coast Banksia species? Other small ornamental Eucalypts? 

[richtrav]

Oh man, this topic again. I’m down in far South Texas and while our temperatures aren’t as low as the northern Gulf we have additional issues with soil alkalinity and salinity that you don’t have. My successes have been very few: Lysiphyllum carronii, Melaleuca bracteata, and cultivars of Callistemon viminalis and blue Eucalyptus coolabah from Texas and Arizona respectively. All Corymbia spp I know of in the area were severely damaged in last year’s freeze, including what should be some of the hardier ones such as tessellaris. There is one Eucalyptus pilligaensis in Weslaco that survived the freeze without losing branches, go figure. The Australian livistonas survived the ‘21 freeze down here, though muelleri and some forms of rigida had heavy foliage scorch. A Eucalyptus victrix I had in a large pot had some branch dieback but came back fast. And Casuarina glauca and presumably cunninghamiana are widely used here, though damage to glauca in the freeze was all over the map, ranging from fine to completely dead. The soil here pretty much rules out the Proteaceae. Lysiphyllum cunninghamii had modest branch damage but recovered well.

Failures would include: Acacia aneura, cana, salicina and stenophylla (though there are a few stenophylla around still limping along), Atalaya hemiglauca (froze way back in ‘21 then died of root rot); Grevillea striata (died from some mystery disease in a pot); Melaleuca fluviatilis and what I think was viridiflora (froze to the ground only to come back chlorotic); Melaleuca tamariscina (it just slowly went away); multiple Eremophila spp, though I have one ‘Wendy’ left that somehow was spared from the freeze; Pittosporum angustifolium (you can get about 10-15 years sometimes out of them); Brachychiton spp (root rot, you’ll see a few populneus around though they lost limbs in ‘21); Callistemon viminalis ‘Slim’ and ‘MacArthur’ (chlorosis, though ‘Slim’ and ‘Little John’ did very well in last year’s cold here); that Monrovia Callistemon rigida type, can’t remember the name, it didn’t like the soil, neither did ‘Harkness’ and to a lesser extent ‘Captain Cook’; pretty much all of Ozbreed’s strappy plants (Lomandra, Dianella, etc); Araucaria bidwillii (one in Weslaco died of some mystery disease years ago). Australian Peltophorum pterocarpum froze down but came back in 2018 and 2021. That’s about all I can think of at the moment, I’m sure there are more. Oh, I lost one of two Macrozamia moorei in the freeze, it took it nearly a year to die.

Still have to put Callistemon viminalis from Boulia in the ground but so far it likes it, it even takes my really bad well water. Callistemon is probably the most successful genus for the Gulf Coast area, they hybridize readily and some of the species have a high level of cold tolerance while others tolerate some alkalinity so the genetics are there. Many also grow in flushes during the warmer months instead of continuously, which is rare among the Australian plants and helps them in winter.

The temperature swings and absolute minima in winter along the Gulf Coast are just too severe for nearly any Australian plant over the long term unless you’re ok with losing all top growth from time to time. Eastern China has been the go-to region for foreign plants in the US for good reason: they have a continental climate similar to the eastern and southern US and many of their plants rely on day length to go into or come out of dormancy. The evolution of the Australian flora has been optimized for a “grow whenever you can” pattern which is ideal where drought is a bigger threat than cold. But that sets them up for disaster on the capricious US Gulf Coast and Southeast.

 

[thyerr01]

Thanks for the detailed thoughts @richtrav. I wasn't aware of the issues with high soil pH/chlorosis in South Texas.

Was your C. vimminalis 'Boulia' grown from seed? That's an unusual locale. I forgot to mention I also have C. vimminalis 'Boyette'. Most of the 'Little John' used in commercial plantings froze back and were removed in my area of Houston, the only ones I have seen that actually recovered were in Galveston.

I have no issues with treating small Eucalypts as die back perennials every couple of years and many will flower at a small size. I am sticking to fire-adapted species with lignotubers which should enable them to survive freezes and form multi-stemmed clumps. The biggest issue will just be rotting from the constant moisture and humidity which hopefully my raised, sandy beds will fix. I am hopeful for some of the Grevillea victorieae complex and hybrids; after doing nothing for six months they all just started new growth with the warmer weather.

I agree that East Asia is a great place to find interesting plants for the gulf coast - I have several palms from there.

[richtrav]

Yes I grew ‘Boulia’ from seed, got it from trees growing in front of the Desert Channels office in Longreach. ‘Boyette’ is a beautiful weeping cultivar from the Bradenton area of Florida that also has some pH issues and about average hardiness for a viminalis. Sure you can try some tropical mallees, they grow faster than than the ones from drier country and there are some such as ptychocarpa that grow in poorly drained sites. Mine froze down in ‘21 but regrew fast, though it hates the high pH of river or well water. Apparently there used to be a place near Hobby airport that had some ptychocarpa and other odd eucs planted out. I have no idea what happened to it, Xenon could probably tell you more about it.

Yeah grevilleas would be fun to play with as temporary ornamental flowering plants in Houston, not so much here, there were a number in Rockhampton that looked great in their Florida-like summer weather. I want to say Grevillea banksii was a parent to many of them. They just have too many soil issues here, robusta can be grown here on lighter soil if you just use city water on it but they had some damage in ‘21. The old Gardens nursery in Austin had some dwarf Grevillea that looked like ‘Long John’ that they used up until 2010 or 2011 I guess. Forgot to mention Casuarina ‘Cousin It’ will grow here but has no vigor, am not sure why. For some reason it does not develop a good root system. I did not see it used much in western Queensland either but it looked great in Brisbane. 

[thyerr01]

Yeah, I saw the old posts about the place in South Houston that had several different Eucalypts. I thought some other folks in Houston were also growing C. ptychocarpa. I'll have to look into some tropical mallees, all my other seeds are WA or arid zone species which are likely to struggle.

I've seen Grevillea 'Peaches and Cream', 'Long John', 'Kings Fire' and 'Kings Celebration' sold locally at Caldwell nursery and G. victorieae has been offered in the past by the John Fairey Garden. They were expensive and probably not popular.

[ShadowNight030]

I have good luck with Grevillea ‘peaches and cream’ and ‘bonfire’ in central Louisiana. I also have luck with various callistemon, with them being popular for landscapes across the gulf coast. My callistemons all survived our low of 12/13F in 2021, with my larger species getting killed to the roots, and my ‘Little Johns’ only defoliating with a few sheets on top. Others in the area are regrowing from their roots slowly. Eucalyptus cinerea is popular in my area. Further south in New Orleans I’ve seen various species I haven’t been able to identify. Someone had a rainbow euc for awhile before Hurricane Ida took it out this past season. A nursery in Lafayette sells various grevilleas and leptospermum. They also have nice sized acacia baileyana ‘purpurea’. I am also interested in trying different eucs, though I’d most likely be better off getting those from seed. 

[ShadowNight030]

Here is my grevillea ‘bonfire’ after 22F. It fared better than my bottlebrush ‘little John’’s did. I have pruned it by half as I read a spring pruning helps with blooming. 

[richtrav]

This is the one they used to grow in Austin pre-2010: