Botany Photo of the Day

I'm curious as to the hardiness of this species of Eucalyptus in your area. Down here in SW Washington, I see an occasional eucalypt, but I haven't seen the one you have featured today. The name "Tasmanian Snowgum" would seem to imply it is fairly hardy.

This plant has been in the ground since 1992, and wasn't harmed at all by the killing frost from a few years ago which wiped out Banksia marginata and Acacia baileyana. UBC has a fair Eucalyptus collection, though at least a few have to be put through the crucible of sustained low winter temperatures.

Maybe Brent Hine will comment - I'll send this along to him.

I should also note that the garden is conducting some Eucalyptus field trials, and I believe one of the assessments is measuring hardiness.

This noble and beautiful Eucalyptus is hardy - at this site - to at least -12c, or 10F. As you see by its accession number it was planted in 1992 or perhaps 1993. It has endured this amount of cold without significant damage at least twice since then. As always in PNW plant trials of these kinds, provenance is crucial. Where did the seed come from? In the end, vagaries of local climate combined with provenance give mixed results. We may have a specific Eucalyptus in local gardens for 5 to 25 years or more, or just two, before it is killed outright or cut down during winter to begin again from the root (e.g. E. gregsoniana, 35741-474-01 now again at 1.5m ht.). Here at UBCBG, we're but 200 meters away from and 100 above the Pacific Ocean. This site gives us a longer and more moderate growing season than just an hour's drive inland. As a result, tissues have more time to harden off before any deep cold of true winter arrives, while cold is less intense. The first "cold snap" (-5c/23F or colder) occurs here most years sometime in December. The plants' evergreen leaves begin photosynthesizing again in earnest in February when temperatures are reliably above freezing. With a growing season roughly nine months long, it isn't too surprising that gardeners are able to succeed with subalpine species. There are currently 14 Eucalyptus taxa in the E.H. Lohbrunner Alpine Garden at the UBC Botanical Garden. Finally, the specimen pictured is yearly depositing viable seedlings into the garden.

Last wipeout winter in Seattle area was 1990--two years before specimen shown here was planted. At the moment gums are common in Seattle. Most-but not all-earlier specimens destroyed or spoiled 1990.

Jacobson, TREES OF SEATTLE - SECOND EDITION reports (under E. coccifera) that "Arboretum has one 40' x 3' 8 1/2" (#501-90A SE of GVC parking lot--it may be a hybrid with Silver Peppermint, E. tenuiramis Miq.)" and that "9808 35th Ave SW has a young tree 21' tall by the road (other species there as well)".

Elsewhere it has been claimed hardiness of seedlings out of same capsule can vary significantly, from all dead through partly dead to intact after a trial winter.

We have found a number of Tasmanian Eucalyptus species to be relatively hardy at our UBC site. This individual was grown from seed in our nursery and planted out as a "5 gallon" in 1991. The winter of 1991 - 1992 was fairly cold and the tree was killed back to the ground (this probably had more to do with the soft growth produced under protected conditions in the nursery than the species' inherent hardiness), but six stems arose from the base the following spring and the tree hasn't looked back. In fact, the following January (1993), the temperature dipped to minus 14C and the tree was unharmed.

We have noticed that a number of local nurseries are beginning to carry Eucalyptus coccifera. Seed is available commercially in Tasmania, but I suspect that people are pocketing seed capsules from this tree and germinating the seeds. We don't permit the removal of any plant materials from the garden, but recognize that when we have a good thing, people will do whatever they can to acquire it. And obviously, this is a tree worth having. Unfortunately, eucalypts are notoriously difficult (nigh-on impossible) to propagate vegetatively and single trees seldom produce enough viable seed for us to realistically consider packaging and selling it in the Shop in the Garden.

To that end, we are growing more individuals of this species (and a number of others) in our nursery, and we are supporting ongoing research in vegetative propagation of Eucalyptus and other recalcitrant species (including Holboellia--see BPotD May 25th). With any luck, this tree will be a more familiar sight in this area within a few years.

PLANT LOCATOR - WESTERN REGION (2004, Black-Eyed Susans/Timber) lists 7 sources for this species:

Forestfarm
Colvos Creek Nursery
Daryll's Nursery
Heronswood
Steamboat Island Nursery
Cistus Nursery
Trans-Pacific Nursery

Wow, thanks for all the comments regarding the hardiness of this species. Best of luck with all your efforts with Eucalyptus.

There is a list of Eucalypts suitable for cold climates at http://www.anbg.gov.au/gnp/cold-climate/eucalypts-cold-climates.html

The Snow Gum Eucalyptus pauciflora is the most cold resistant and characterised by beautiful bark.

M. Lee, Colvos Creek Nursery has recommended E. archeri as the hardiest here. Otherwise, E. perriniana has made some of the most resilient specimens. One Seattle site even had it reseeding before the 1990 winter. Horticulture Center of the Pacific, near Victoria has a largish one as a centerpiece.

This picture confirms Ken's statement regarding the bark of Eucalyptus pauciflora, attached picture, taken September 27, 2005, is ssp. niphophila bark.

The bark of pauciflora is even more impressive

or

Finally, the specimen pictured is yearly depositing viable seedlings into the garden. . .

Will it turn out to be invasive?

The penultimate one looks like one of Boucher's nymphs' buttocks but spraypainted. You can tell I'm spending too much time at camp accessible only by snowshoes sitting atop a rock which gets sprayed in November storms by Lake Superior waves but just last night the hither bay got finally frozen and is calmed at last. Made a liar out of me despite a rise from -15 to -5 only and barely any wind the dark green water reclaimed the ice and it's restless normally again. Finally before the frost hit two months ago I ate the lonely rosehip of the only wild rose on a single stem as it barely got ripened at last.