Articles | Home | Back

Recent Northwest Freezes and the Olympia Garden

In the early 2000's it seemed everyone was pretty happy about the Northwest's gardening climate. Mild winters followed one after the other and the severe winters of the 80's were nothing but a distant memory. Gardeners increasingly pushed the boundaries of what could be grown in western Washington, Oregon and British Columbia with plants frost hardy to only 20 - 25°F, or even less hardiness in really protected gardens.

A moderate freeze in January 2004 and another in November 2006 served as reality checks for gardeners in some areas. Still, even these events were not as severe or damaging to plants as the cold winters of the 80's. Then along came the big freeze of December 13 - 23, 2008, bringing severe cold (sub-zero in some cases) to regions north of Seattle, including Vancouver's coldest official temperature in 40 years, and 2 - 3 feet of snow from multiple storms. From Seattle southwards, the cold was relatively less severe in December 2008, but another freeze on December 6 - 13, 2009 caused significant plant destruction to areas south of Seattle, and all the way into California, where Redding recorded a new all-time low in its more than 100 year period of record (16°F). This freeze evolved quite differently (bringing virtually no snow, for one thing) and spared gardens from Seattle north to varying degrees, with some lucky folks barely having any serious frost.

It follows, then, that all the marginally hardy species I planted at my previous garden near Olympia got more of a serious test in December 2009 than in 2008, since Olympia is situated south of Seattle. The garden I refer to is not in Olympia proper, but a few miles northwest of the city center, not far from the Evergreen State College. Winter temperatures here are significantly milder than those recorded at the Olympia airport, which misrepresents the Olympia area as being some sort of terribly cold place. For example, during a severe freeze in December, 1998, the Olympia airport recorded a temperature of -1°F while it was no colder than 14°F at my garden on the same night.

In the freeze of December 2008, the minimum temperature at the Olympia garden was about 18°F. (I have to say "about" since the effects of differing microclimates cause a couple degrees of variation in the exact temperature to which each plant was exposed.) However, the temperature remained below freezing for most of 10 consecutive days, which it still quite a test for plants that are not accustomed to frigid weather. It also snowed about two feet over the period. Of course the insulation provided by snow cover is mostly advantageous for marginally hardy plants, as it protects their roots, and (to some degree) lower branches from freeze damage. Certain plants that appreciate good air circulation at all times may have had difficulty being buried under snow for such a long period, however.

In the freeze of December 2009, the minimum temperature at the Olympia garden was about 12°F. This time there was no snow cover to protect the roots of plants from freezing and it can be assumed the soil froze to a depth of several inches. The temperature remained entirely below freezing for nearly a week. Also, because this freeze occurred slightly earlier in the winter, plants were a little bit less "hardened off" than they would have been in the 2008 freeze. This was a good test for the plants since the Northwest is prone to occasional early very hard freezes, even in November some years (1955, 1985).

We also had significant freezes at the Olympia garden in February 1989 (minimum 13°F), December 1990 (minimum 9°F), and December 1998 (minimum 14°F). (The big December 1996 snow actually did not manage to bring severe cold as far south as Olympia.) December 1990 is often considered the historic "landmark freeze" for most of the West Coast from Seattle southwards: even those with a very conservative view of plant hardiness generally agree that "if it survived that, it can survive anything." February 1989 was the comparable "landmark freeze" north of Seattle. The December 1998 freeze was somewhat less severe overall, despite hitting southwest Washington and western Oregon pretty hard.

I think it's fair to say based on plant damage, the minimum temperature, early timing of the freeze, and complete lack of snow cover, that the December 2009 freeze was slightly more severe than the December 1998 freeze (which was later and had a few inches of snow cover) for my Olympia garden. That makes the December 2009 freeze the worst this location has seen since December 1990. To me, it almost qualifies as a "landmark freeze", but not quite; and was very instructive in learning what plants are hardier than realized, which deserve further experimentiation, and which we might consider giving up on growing in the Northwest.

The Plants

The Olympia garden is on a slight west-facing slope. The soil is very heavy clay which drains poorly (somewhat poorly to very poorly, depending on the location) in winter. In summer it dries up and becomes cracked (like a lake in the desert) for the dry period from about July through September. Annual precipitation averages about 60 inches, with (like the whole Northwest) a very strong winter maximum.

I began major planting of marginally hardy plants in Olympia around 1995 - 96. Although certain species froze out in December 1998, I continued planting until about 2006. A great deal of planting was done during my college years from about 1999 - 2002. So everything in the report below has been well established for years. However, certain plants have not put on growth, because of suboptimal conditions usually resulting from too much competition for light and water from surrounding plants. Especially in the case of eucalypts, which were often planted too close together, the earlier planted and more vigorous specimens vastly outgrew the later plantings. Perhaps now that some of the larger, older ones have frozen out, some plants that have struggled along for years will finally have their day.

Results

The chart below lists the plants in my garden and their performance through the winters of 2008-09 and 2009-10. In the second and third columns below I provide my best visual estimate of the degree of freeze damage to the plant listed in the first column. Where multiple plants of the same species and origin were planted, I sometimes list them individually, but sometimes I just provide a note of how many there were. In the white boxes I offer some additional commentary where warranted. Further conclusions about this grand experiment can be found below.

Botanical Name	Damage Winter 2008-2009	Damage Winter 2009-2010
Abutilon vitifolium	no damage	didn't really pay attention, but looked fine in July
Acacia dealbata var subalpina [Celyn Vale]	one with 20% leaf burn, others undamaged	all dead to ground
Acacia dealbata var subalpina [Celyn Vale]	(big one) no damage	dead to the ground, a few shoots coming up from ground level
Many had high hopes for this, reportedly one of the hardiest Acacias. I originally planted four; they were beautiful in flower and bloomed all winter every year. I think we can fairly conclude it is hardy to about 15°F in the Northwest. It also appears to be a less vigorous resprouter from the ground than regular A. dealbata.
Acacia pravissima	minor damage	dead
Acaena microphylla	no damage	no damage
Aloe striatula	frozen to ground, resprouted	not appearing yet as of July
Araucaria angustifolia	no damage	no damage
Araucaria bidwillii	dead	still dead
Argyrocytisus battandieri	slight tip dieback	no damage other than normal leaf loss
Austrocedrus chilensis	no damage	no damage
Azara lanceolata	no damage	some leaf loss, no dieback
Bashania fargesii	no damage	no damage
Callistemon (mystery sp. cute!)	(no information)	slight damage
Callistemon 'Cole's Hybrid'	dead to ground, resprouting	dead
Callistemon linearis [Colvos]	(no information)	defoliated, regrowing throughout
Callistemon macropunctatus	dead	still dead
Callistemon pallidus [Forestfarm]	no damage	80% leaf burn
Callistemon pallidus [silver form]	no damage	dead to the ground, resprouting
Callistemon pityoides [Xera]	no damage	no damage
Callistemon rigidus	10% leaf burn	dead
Callistemon sieberi 'pink form'	(this is probably not really a form of C. sieberi) heavy leaf burn	dead
Callistemon sieberi prickly version	no damage	no damage
Callistemon sieberi slightly less prickly version	no damage	no damage
Callistemon sp. [Mt. Drummer]	no damage	dead to the ground, resprouting
Callistemon sp. [not brachyandrus]	10% burn	dead, not resprouting
Callistemon sp. [Red Giant]	no damage	dead to ground, resprouting
Callistemon sp. [Soft White]	slight damage	dead to the ground, resprouting
Callistemon sp. [Woodlander's Hardy]	10% burn	20% burn/dieback
Callistemon sp. aff. salignus [WCM]	no damage	no damage
Callistemon sp. aff. sieberi small hairy	no damage	no damage
Callistemon sp. aff viridiflorus	(probably a form of C. sieberi, actually) no damage	no damage
Callistemon sp. 'Ken's Favorite'	no damage	about 60% burn/dieback
Callistemon sp. 'Violaceous'	20% leaf burn	dead to the ground, resprouting
Callistemon sp. 'Waldport Hardy'? 'Woodlander's Red'?	no damage	dead
Callistemon subulatus	no damage	about 60% burn/dieback
Callistemon subulatus	no damage	30% leaf burn
One of the consistently hardiest non-white-or-cream flowered Callistemons, C. subulatus blooms bright red. Despite some foliage burn these all looked reasonably good by summer.
Callistemon viridiflorus	no damage	90% leaf burn but resprouting at 6' up
Callistemon viridiflorus [Jim G.]	no damage	no damage
I believe we have now discovered a form of this species with superior hardiness, which I will be propagating in the future. The one that froze was much larger.
Callistemon x 'Eleanor'	no damage	dead to the ground, resprouting
Carpenteria californica	no damage	no damage
Cassinia fulvida	no damage	minor leaf burn, no real damage
Ceanothus 'Blue Jeans'	no damage	no damage
Ceanothus 'Julia Phelps'	no damage	no damage
Ceratostigma plumbaginoides	no information	dead to ground, resprouting
Chamaedorea microspadix x radicalis	parts above snow dead, resprouting	parts above ground dead, resprouting very feebly
Chamaerops humilis	dead	still dead
Chamaerops humilis [seed grown]	no damage	no damage
The dead one had been transplanted recently and was not fully re-established. The other had been in the ground for years. All you people who are constantly rearranging the palms in your garden take note!! (I would also suggest that the surviving one benefitted from not having any summer water, which helped it to harden off.)
Choisya ternata	no damage	slight damage, looked great by summer
Chusquea culeou	no damage	no damage
Chusquea gigantea (breviglumis)	no damage	no damage
Chusquea valdiviensis	no damage	frozen to ground, resprouting weakly
Planted in 2000, this exciting climbing bamboo from Chile had grown more than 60' high into a sitka spruce tree and was magnificent and beautiful. Its recovery remains uncertain.
Cissus striata	slight damage	frozen to ground, resprouted vigorously
Clerodendrum bungei	no damage	no damage
Cordyline australis	minor burn on lower leaves	dead to the ground, one coming back, another not
Cordyline australis 'Baueri'	dead to the ground, grew back	dead to the ground, grew back
Cordyline indivisa	dead	still dead
Corokia macrocarpa	no damage	dead to about 1' above ground
Corokia virgata 'Bronze King'	no damage	dead
Crinodendron hookerianum	slight tip dieback	dead to about 2' above ground
Crinodendron hookerianum	no damage	a little damage
Crytomium falcatum	(no information)	dead
Cupressus lusitanica var. lindleyi	no cold damage, but top broke off in snow	no damage
Cupressus macrocarpa	no damage	no damage
Cupressus macrocarpa 'Donard Gold'	no damage	no damage
Desofontainia spinosa	no damage	no damage
Dicksonia antarctica	slight damage	defoliated, but coming back
It should be noted that this was protected with blankets during both freezes. Even so, I think its survival of the 2009 freeze was a close shave. It has been in the ground since 1996.
Distylium racemosum	no damage	no damage
Edgeworthia chrysantha	on its way out	dead
Elaeagnus x ebbingei	no damage	no damage
Embothrium coccineum	no damage	no damage
Erica arborea var. alpina	no damage	no damage
Eriobotrya japonica	no damage	no damage
Eryngium agavifolium	no damage	no damage
Eryngium sp. [Woodlanders]	no damage	no damage
Eucalyptus acaciiformis [Chiltern Seeds]	(2 trees) 10% burn	dead to the ground
Eucalyptus aggregata [Milligan Seeds]	(3 plants) no damage	dead to ground, two are resprouting
Although E. aggregata is often compared with E. rodwayi, apparently the latter is superior.
Eucalyptus amygdalina [Milligan Seeds]	no damage	dead to the ground, resprouting
Eucalyptus apiculata [Milligan Seeds]	no damage	dead to the ground, resprouting
Eucalyptus archeri [Burnt Ridge]	no damage	heavy leaf burn, but no dieback, also major resprouting
Eucalyptus archeri [Celyn Vale?]	(2 plants) no damage	no damage
Eucalyptus archeri x nitens [Milligan Seeds]	no damage	mostly dead, resprouting at 4'
Eucalyptus badjensis [Milligan Seeds]	one fine, one dead to trunk	both dead
Eucalyptus badjensis [Milligan Seeds]	60% burn/dieback, resprouting from trunk	dead to the ground
Eucalyptus baeuerlenii [Milligan Seeds]	dead to about 6" above ground	dead
Eucalyptus barberi [Wildseed]	(no information)	frozen to ground, resprouted
Eucalyptus bicostata [Milligan Seeds]	heavy damage, resprouting	dead
Eucalyptus bicostata [Milligan Seeds]	dead	still dead
Eucalyptus bicostata [Milligan Seeds]	60% leaf burn, branches ok	dead
Eucalyptus bridgesiana	20% burn of older leaves	dead
Eucalyptus bridgesiana [Frank]	80% leaf burn but branches fine	dead
Eucalyptus brookeriana [Milligans]	dead	still dead
Eucalyptus brookeriana [Milligans]	(no information)	dead to the ground, resprouting
Eucalyptus brookeriana [Milligans]	(in an excellent microclimate) no damage	top dead, resprouting to about 8' up
Eucalyptus camphora [Milligan Seeds]	(3 plants) (no information)	defoliated, but releafing throughout
Eucalyptus camphora [Milligan Seeds]	(no information)	dead to the ground, resprouting
I'm very impressed with this species. Even if leaves and small branches die it seems very capable of releafing and recovering quickly throughout the plant rather than just freezing to the ground. The one that died to the ground may have been a victim of "weedwhacker blight."
Eucalyptus chapmaniana [Milligan Seeds]	no damage	defoliated, resprouting from about 1' up
Eucalyptus cinerea	20% burn of older leaves	dead
Eucalyptus cinerea [California]	30% leaf burn	dead
Eucalyptus coccifera [Celyn Vale]	(2 trees) no damage	dead, one of two is resprouting
Eucalyptus coccifera [Milligan Seeds]	no damage	dead to the ground, "tried" to resprout, but regrowth died
Eucalyptus cordata [Milligan Seeds]	(5 trees) no damage	dead to the ground, resprouting
Eucalyptus cordata [Chiltern Seeds]	20% crisped	dead, resprouting from base
Eucalyptus crenulata [Milligan Seeds]	no information	about 70% burn, trunk severely split, but no real dieback, looks like it will be fine?
Eucalyptus crenulata hybrid [Milligan Seeds]	no damage	no damage
Eucalyptus crenulata x nitens [Milligan Seeds]	no damage	dead
Eucalyptus dalrympleana [Burnt Ridge]	50% burn	dead to the ground
Eucalyptus dalrympleana [Milligan Seeds]	(2 trees) no damage	slight tip damage, 20-30% defoliated, resprouting
Eucalyptus dalrympleana [Milligan Seeds]	no damage	dead to the ground, resprouting
Eucalyptus dalrympleana [Milligan Seeds]	(2 trees) no damage	no damage
Eucalyptus delegatensis [Colvos Creek]	30% leaf burn	50% burn but branches still alive, ought to make it
This unique plant of unknown seed origin was very glaucous, with smaller leaves than usual and looked rather like a snowgum when I bought it; however, it's definitely E. delegatensis. I hope this excellent hardy form produces seed someday!
Eucalyptus delegatensis [Milligan Seeds]	no damage	dead, but it appears to have "almost survived"
Eucalyptus dendromorpha [Milligan Seeds]	dead	still dead
Eucalyptus dives [Milligan Seeds]	(it's in too much shade) ok	heavy leaf burn, resprouted at 2'
Eucalyptus dunnii [Nindethana]	nearly defoliated, almost all of tree looks dead	really dead
It had been a huge, 50' tree in my most protected microclimate.
Eucalyptus elliptica [Milligan Seeds]	no damage	dead
Eucalyptus elliptica x nitens [Milligan Seeds]	no damage	(little one) dead to ground, resprouting
Eucalyptus elliptica x nitens [Milligan Seeds]	no damage	(huge one) about 70% dieback, some branches alive?
The future of this massive, beautiful tree is uncertain. It has smooth colorful bark that smelled very fruity!
Eucalyptus elliptica x pulverulenta [Milligan Seeds]	no damage	dead to the ground, resprouting
Eucalyptus fastigiata [Milligan Seeds]	no damage	about 60% leaf burn, branches ok
Eucalyptus fastigiata [Milligan Seeds]	40% leaf burn	dead
Eucalyptus glaucescens [Celyn Vale]	no damage	trunk split, no other damage
Eucalyptus glaucescens [Celyn Vale]	no damage	dead to the ground, resprouting
Eucalyptus glaucescens [Celyn Vale]	no damage	no damage
Eucalyptus glaucescens [Chiltern Seeds]	no damage	top dead. Resprouting @ about 8' up
It's certainly disappointing that one of the Celyn Vale plants froze to the ground - this is generally regarded as one of the hardiest eucalypts. The Chiltern tree was planted in 1996 and was undamaged through the December 1998 freeze.
Eucalyptus glaucescens? Hybrid [Celyn Vale]	no damage	dead to the ground, resprouting
Eucalyptus globulus	dead to trunk, resprouted from main trunk	dead to the ground
Eucalyptus goniocalyx?	dead	still dead
Eucalyptus gregsoniana [Chiltern Seeds]	no damage	20% defoliated, trunk split, but ought to be fine
Eucalyptus gunnii [provenance unknown]	no damage	dead to the ground, resprouting
Eucalyptus gunnii [Silverdrop]	(8 trees) no damage	no damage
Eucalyptus gunnii [Silverdrop]	no damage	dead to the ground, resprouting
Eucalyptus gunnii var divaricata	no damage	no damage
Eucalyptus hybrid (nicholii x ???)	no damage	defoliated, resprouting all along trunk to top!
Eucalyptus hybrid [parvula x ?]	no damage	dead
Eucalyptus johnstonii (hybrid?) [Celyn Vale]	no damage	10% leaf burn
This may have been a hybrid with E. gunnii, I'm not sure. Unfortunately it fell down sometime in spring 2010 and is no longer with us.
Eucalyptus johnstonii [Milligans]	(in a very protected microclimate) no damage	top dead, resprouting to about 10' up
Eucalyptus kartzoffiana [Frank]	(2 trees) dead? Defoliated anyways	still dead
Eucalyptus kitsoniana [Milligan Seeds]	(2 trees) no damage	dead to the ground, resprouting
Eucalyptus kybeanensis [Celyn Vale]	no damage	lower lvs/brs dead, but mostly fine
Eucalyptus lacrimans [Celyn Vale]	(small and in too much shade) no damage	died back to trunk, resprouting from 5' up
Eucalyptus lacrimans [Celyn Vale]	(2 trees) no damage	no damage
Eucalyptus ligustrina [Milligan Seeds]	90% burn and trunk is split, not looking good	dead
Eucalyptus macarthurii [Milligan Seeds]	(2 trees) no damage	dead to the ground, has resprouted vigorously
Eucalyptus mannifera	20% leaf burn on older leaves	dead
Eucalyptus mannifera praecox (E. praecox) [Milligan Seeds]	no damage	about 20% leaf burn, looked fine by summer
Eucalyptus mitchelliana [Milligan Seeds]	(2 trees) no damage	no damage
Eucalyptus moorei [Milligan Seeds]	no damage	dead to the ground
Eucalyptus moorei nana	no damage	dead, resprouting from base
Eucalyptus morrisbyi [Wildseed Tasmania]	(3 plants) moderate to heavy leaf burn	all dead to the ground, resprouting
Eucalyptus morrisbyi x dalrympleana? [Wildseed]	moderate leaf burn	dead to the ground, resprouting
Eucalyptus neglecta [Trans-Pacific Nursery]	no damage	no damage
Eucalyptus neglecta [Milligan Seeds]	no damage	10% leaf burn
Eucalyptus neglecta [Milligan Seeds]	no damage	no damage
Eucalyptus nicholii [Celyn Vale]	no damage	was cut down before winter, did not resprout (was 50' tall)
Eucalyptus nitens (Chilean landrace) [GIT]	(no information)	dead
Eucalyptus nitens [Milligan Seeds]	no damage	dead
Eucalyptus nitens [Victoria BC]	(2 trees) 10% leaf burn	dead, one resprouting from base
Eucalyptus nitida [Celyn Vale?]	no damage	dead
Eucalyptus nova-anglica [Milligan Seeds]	no damage	no damage
Eucalyptus obliqua [Milligan Seeds]	(in too much shade) dead	still dead
Eucalyptus ovata? Yarraensis? [Milligan Seeds]	90% defoliated, regrowing	dead to the ground, resprouting
Eucalyptus paliformis [Milligan Seeds]	no damage	dead
Eucalyptus parvula [Celyn Vale]	no damage	about 30% burn to lower lvs
Eucalyptus parvula [Chiltern Seeds]	no damage	no damage
Eucalyptus parvula x nitens [Celyn Vale]	no damage	no damage
Eucalyptus parvula x pulverulenta [Celyn Vale]	no damage	no damage
Eucalyptus pauciflora [Mt. Buffalo]	no damage	no damage
Eucalyptus pauciflora subsp. debeuzevillei [Celyn Vale]	(2 plants) no damage	no damage
Eucalyptus pauciflora subsp. debeuzevillei [Milligans]	no damage	some damage to trunk/bark, top still growing fine
Eucalyptus pauciflora subsp. niphophila [Nungar Plain]	no damage	no damage
Eucalyptus pauciflora subsp. pauciflora [Chiltern Seeds]	no damage	70% leaf burn, trunk cracked, but top keeps growing
Eucalyptus pauciflora subsp. pauciflora [Milligan Seeds]	(4 plants) no damage	one undamaged. 3 dead to ground, resprouting
Eucalyptus perriniana (mainland) [Celyn Vale]	no damage	no damage
Eucalyptus perriniana (mainland form) [Milligan Seeds]	no damage	60% burn
Eucalyptus perriniana (Tasmania) [Burnt Ridge]	minor leaf burn	dead to the ground, resprouting
Eucalyptus perriniana (Tas. Form) [Milligan Seeds]	no damage	30-40% leaf burn, ought to be fine
Eucalyptus pulverulenta [Celyn Vale]	(no information)	defoliated, resprouted to 9' up trunk
Eucalyptus quadrangulata	(no information)	dead
Eucalyptus radiata [Milligan Seeds]	dead to trunk, resprouted from main trunk	dead
Eucalyptus radiata [Milligan Seeds]	dead, tried to resprout a little	still dead
Eucalyptus regnans [Milligan Seeds]	about 50% leaf burn, but no dieback	dead
Eucalyptus regnans [Milligan Seeds]	(was in too much shade) dead	still dead
There's quite a bit of interest in Eucalyptus regnans, since it is the world's tallest non-coniferous tree, having been recorded to grow at least 373' tall in the wild. Despite coming from a cool, moist, maritime climate, often at rather high altitudes, this tree doesn't quite have what it takes to survive a colder Northwest winter. The larger one - the one that managed to survive December 2008 - was 70' tall when it froze dead. Unlike many eucalypts it's also incapable of returning from the roots if the top is killed.
Eucalyptus retinens [Frank]	dead	still dead
Eucalyptus rodwayi linear juvenile lvs [Milligan Seeds]	no damage	no damage
Eucalyptus rodwayi round juvenile lvs [Milligan Seeds]	no damage	no damage
Eucalyptus rubida [Celyn Vale]	no damage	dead to the ground, resprouting
Eucalyptus rubida [Chiltern Seeds]	10% leaf burn	no damage
Eucalyptus rubida [Frank]	90% crispy	dead, resprouting from base
Eucalyptus rubida [Milligan Seeds]	90% burn	dead to the ground, resprouting
Eucalyptus rubida is one of the most beautiful hardy Eucalyptus species. It's surprising that the Chiltern provenance was unharmed in December 2009, since the top of it froze back a couple feet in the January 2004 freeze. The Celyn Vale form was exceptionally beautiful, and I hope for seed of it someday when it grows back. I had a much larger one, but it fell over in 2006 - pity.
Eucalyptus rubida x nitens [Celyn Vale]	no damage	dead, but appeared to "almost survive"
Eucalyptus rubida x viminalis [Celyn Vale]	slight damage	dead
This was my tallest eucalypt at more than 80' tall. It was one of a number of eucs that appeared to "almost survive" - meaning, it did not show certain damage until very late in the spring and then the whole thing collapsed probably from internal damage that prevented the transport of water and nutrients to the plant.
Eucalyptus scoparia [Forestfarm]	some leaf burn on lower lvs	dead
Eucalyptus sp. aff lacrimans [Celyn Vale]	no damage	20% leaf burn, looked great by summer
Eucalyptus sp. was supposed to be saxatilis [Milligans]	(uncertain just what this is, likely a hybrid) no damage	dead to the ground, resprouting
Eucalyptus stellulata [Chiltern Seeds]	no damage	no damage
Eucalyptus subcrenulata [Celyn Vale]	(no information)	dead
Eucalyptus subcrenulata [Milligan Seeds]	no damage	60% leaf burn, regrowing throughout
Eucalyptus subcrenulata [Milligan Seeds]	no damage	no damage
Eucalyptus urnigera (Mt. Field, Tas) [Frank]	(5 plants) no damage	mixed: some dead, resprouting; some fine
Eucalyptus urnigera [Luke Isham]	no damage	90% burn, top half is dead, ought to recover
Eucalyptus urnigera [Milligan Seeds? Not sure]	(no information)	dead
Eucalyptus urnigera x dalrympleana [Celyn Vale]	(3 plants) no damage	minor leaf burn, no real damage
Eucalyptus urnigera x nitens [Milligan Seeds]	no damage	50% defoliation, top regrowing, and resprouting at base
Eucalyptus sp. aff. vernicosa [Celyn Vale]	(2 plants) no damage	no damage
These were supposed to be E. vernicosa but they grew much larger than E. vernicosa does, and have floral features matching E. subcrenulata. Probably they represent an intergrade between E. vernicosa and E. subcrenulata - they certainly have excellent hardiness!
Eucalyptus viminalis [Celyn Vale]	no damage	dead
Eucalyptus viminalis [Chiltern]	no damage	dead to the ground
The E. viminalis from Celyn Vale, planted in 1999, was 70' tall and awesome - though I had a better one with a beautiful weeping form that blew over in 2006. The Chiltern ones, planted in 1997 and frozen to the ground in 1998, were quite large as well. I guess there's not much point in growing this species in the Northwest though, when the very similiar E. dalrympleana is hardier.
Eucalyptus volcanica [Frank]	10% burn	dead, resprouting from base
Eucalyptus williamsiana	dead	still dead
Eucalyptus youmanii [Milligan Seeds]	one dead, one fine	both dead now, one resprouting from base
Eucryphia x hybrida	no damage	no damage
Eucryphia x intermedia 'Rostrevor'	no damage	no damage
Eucryphia x nymanensis 'Mt. Usher'	no damage	no damage
Eucryphia x nymanensis 'Nymansay'	no damage	no damage
Fargesia utilis	no damage	no damage
Fascicularia bicolor [Edinburgh]	very slight damage	about 40% crisped, crowns mostly ok, recovering
Fascicularia pitcairnifolia	90% burn, but alive	one tiny part remains alive
Fatzhedera lizei	no damage	defoliated, resprouting from near base
Feijoa sellowiana	50% leaf burn	10-20% leaf burn
Ficus carica 'Lattarula'	no damage	no damage
Ficus pumila	no damage	90% leaf burn, but coming back well
Ficus sarmentosa var. nipponica	no damage	no damage
Fitzroya cupressoides	no damage	no damage
Fremontodendron 'California Glory'	(no information)	dead
Fremontodendron 'Pacific Sunset'	no damage	dead
Fuchsia campos-portoi	no information	dead to the ground, resprouting
Fuchsia excorticata	slight tip dieback	frozen to ground, resprouted
Fuchsia magellanica 'Ricartonii'	no damage	frozen to ground, resprouted
Fuchsia magellanica 'Sharpitor Aurea'	frozen to ground, resprouted	frozen to ground, resprouted
Fuchsia magellanica var. molinae	no damage	frozen to ground, resprouted
Fuchsia procumbens	still alive	disappeared for a while, but growing back
Fuchsia regia var regia	(no information)	dead to the ground, resprouting
Fuchsia sp. [Yachats]	(no information)	dead to the ground, resprouting
Gevuina avellana	no damage, but snow knocked it over	no significant damage, but still bent over
Grevillea 'Austraflora Canterbury Gold'	(was in too much shade) no damage	can't even find it, dead I guess
Grevillea 'Canberra Gem'	(was in too much shade) no damage	dead
Grevillea 'Clearview David'	dead	still dead
Grevillea juniperina 'Low Red' or was it 'Molonglo'	(was in too much shade) no damage	mostly defoliated, probably dead
Grevillea juniperina 'Pink Pearl'	(was in too much shade) no damage	dead
Grevillea juniperina var. sulphurea	very slight tip dieback	very slight tip dieback again
Grevillea miqueliana [Heronswood form]	(was in too much shade) no damage	dead
Grevillea miqueliana [UCSC]	(was in too much shade) no damage	dead
Grevillea 'Noellii'	no damage	dead
Grevillea 'Penola Pearl'	no damage	dead
Grevillea 'Poorinda Elegance'	no damage	dead
Grevillea 'Poorinda Leane'	(2 plants) no damage	no damage
Grevillea rosmarinifolia	no damage	90% leaf burn, future uncertain
Grevillea 'Ruby Clusters'	70% defoliated, some dead branches	dead
Grevillea 'Scarlet Sprite'	dead	still dead
Grevillea victoriae	(3 plants) no damage	no damage
Grevillea victoriae 'Marshall's Seedling'	no damage	no damage
Grevillea victoriae 'Murray Valley Queen'	no damage	no damage
Griselinia littoralis	no damage	dead
Gunnera perpensa	no real damage, leaves gone, that's normal	no real damage, lost leaves as usual
Hakea microcarpa? epiglottis? (wish I hadn't lost the label)	no damage	no damage
Hebe albicans	no damage	no damage
Hebe 'Amy', seedling of	no damage, another with heavy damage	all dead
Hebe cupressoides	no damage	about 50% of lower foliage browned out
This damage didn't show until July, so not sure if it's frost damage, or something else.
Hebe glaucophylla	no damage	no damage
Hebe mckeanii	no damage	no damage
Hebe 'Mrs. Winder'	heavy damage	dead
Hebe 'Nicolai's Blush'	no damage	dead
Hebe pin...whatever 'Pagei'	no damage	no damage
Hebe seedling of 'Amy'	no damage	dead
Hebe 'Spender's Seedling'	no frost damage, snow smashed it a bit	some leaf loss, will be ok
Hebe sutherlandii	no damage	no damage
Hebe topiaria	no damage	no damage
Hebe traversii	no damage	no damage
Hebe traversii (another form)	no damage	no damage
Hedera canariensis 'Variegata'	no damage	no damage
Himalayacalamus porcatus	frozen to ground, resprouted	dead to the ground, resprouting weakly
Hoheria sextylosa	lost a lot of leaves, stems fine	dead
Hydrangea integrifolia	no damage	no damage
Hymenanthera alpina	no damage	no damage
Ilex latifolia 'Purple Power'	no damage	no damage
Ilex purpurea	no damage	dead, but perhaps not from cold?
This was in poor condition before the freeze came.
Jubaea chilensis	no damage	dead
This had been in the ground since 2000 and was never damaged despite being in the coldest part of the garden. It was originally in full sun but was heavily shaded by eucalypts toward the end. In December 2009 the leaves were generally undamaged but the plant lost its central spear, the most vulerable point. Of course I can't really prove it but I think it might have been saved if the center had been sprayed with a copper fungicide in the spring before it was too late.
Kniphofia linearifolia	no damage	no damage
Kniphofia northiae	no damage	no serious damage
Kniphofia thompsonii hybrid	no damage	no damage
Kunzea ericoides	80% defoliated, but ok	dead to the ground, resprouting
Lagarostrobos franklinii	no damage	very slight 2% tip dieback, basically fine
Laurus nobilis	no damage	no damage
Leptospermum cunninghamii	no damage	90% defoliated, regrowing vigorously
Leptospermum humifusum [prostrate form]	no damage	no damage
Leptospermum lanigerum	no damage	dead
Leptospermum lanigerum	no damage	dead
Leptospermum lanigerum [purple leaf form]	no damage	95% dead, few live branches, regrowing strongly
Leptospermum nitidum	no damage	85% dead, lots of vigorous regrowth
Leptospermum scoparium [Seattle Hardy]	no damage	80-90% defoliated, resprouting from branches
Leycesteria formosa	no significant damage	dead almost to the ground, regrowing
Lomatia fraseri	no damage	about 50% died back. Bottom 3' of it alive, looked good by summer
Lomatia polymorpha	no damage	no damage
Lomatia tinctoria	no damage	no damage
Lophomyrtus obcordata	defoliated, some dieback	dead
Luma apiculata	very slight damage	about 20% leaf burn, crisped branch tips
Magnolia macrophylla	no damage	no damage
Mangletia insignis	no damage	no damage
Maytenus boaria	very slight tip dieback	no damage
I'm really impressed with this plant - I've been aware of hardy forms of it but I thought they were all inferior looking, while the beautiful weeping ones were supposed to be tender. Apparently I got lucky with this specimen (which is a nice weeping one) and in the future I'll be propagating and selling it.
Medicago arborea	no damage	no damage
Melaleuca linearifolia	heavy damage, looks mostly, but not quite, dead	dead
Melaleuca squarrosa	(no information)	dead
Michelia platypetala	no damage	no damage
Mitraria coccinea	no damage	heavy damage, but growing back from all of plant, ought to be fine
Myrceugenia nanophylla	no damage	no damage
Myrtus communis 'Nanophylla'	(no information)	90% burn/dieback
Myrtus communis 'Variegata'	no damage	60% leaf burn
Nerium oleander 'Hardy Red'	90% defoliated	dead
Nothofagus fusca	no damage	no damage
Nothofagus procera	no damage	no damage
Olearia argophylla	dead	still dead
Olearia avicennifolia	no damage	no damage
Olearia gunniana	no damage	no damage
Olearia lineata 'Dartonii'	no damage, but snow knocked it over	was taken out before winter
Olearia macrodonta	no damage	80% burn, tip dieback, recovered fast, looked great by summer
Olearia moschata	dead	still dead
Olearia traversii	no damage	dead
Olearia x haastii	no damage	no damage
Olearia x mollis	no damage	no damage
Osmanthus fragrans [Seattle Hardy]	no damage	no damage
Osteospermum barberiae	heavy damage, but survived	(no information)
Parakmeria lotungensis	no damage	no damage
Passiflora caerulea	(no information)	dead to ground, resprouted, already huge again by July
Phormium cookianum	no damage	95% dead but coming back
Phormium cookianum	80% crisped	dead
Phormium tenax	dead	still dead
Phormium tenax [bronze]	(was a huge plant) no damage	80% defoliated
Phormium tenax [purple]	35% burn	dead
Photinia serrulata	no damage	no damage
Phygelius capensis	no damage	no damage - wow
Phygelius 'Moonraker'	slight damage	frozen to ground, resprouted
Phygelius 'Salmon Leap'	slight damage	frozen to ground, resprouted
Phygelius 'Winchester Fanfare'	(no information)	dead to the ground, resprouting
Phyllostachys vivax	no frost damage, but snow crushed it	no damage
Pinus patula	no damage	no damage
Pittosporum crassifolium	top died back 1'	dead
Pittosporum eugenioides	no damage	dead
Pittosporum ralphii	no damage	looks like about 80% dead with one branch still alive
Pittosporum tenuifolium	no damage	no damage
Pittosporum tenuifolium 'Silversheen'	no damage	10-20% burn, looked reasonably good by summer
Pittosporum tenuifolium 'Theodore'	no damage	no damage
Pittosporum tobira [Seattle Hardy]	no damage	no damage
Pittosporum x 'Garnettii'	no damage	some leaf loss, no dieback, looked ok by summer
Podocarpus alpinus	no damage	no damage
Podocarpus lawrencei 'Purple King'	no damage	no damage
Podocarpus macrophyllus	no damage	no damage
Podocarpus nivalis	no damage	no damage
Podocarpus salignus	no damage	no damage
Podocarpus totara 'Aurea'	no damage	no damage
Pseudopanax ferox	no damage	no damage
I planted this and P. crassifolius in 2006. P. crassifolius froze dead in November 2006, so I was really impressed that P. ferox survived December 2009.
Quercus agrifolia	no damage	no damage
Quercus chrysolepis	no damage	no damage
Quercus chrysolepis? Vaccinifolia?	no damage	no damage
Quercus douglasii	no damage	no damage
Quercus fusiformis	no damage	no damage
Quercus hypoleucoides	no damage	no damage
Quercus ilex	no damage	no damage
Quercus phyllareoides (sp??)	no damage	no damage
Quercus reticulata (sold as Q. rugosa)	no damage	no damage
Quercus salicifolia? Salicina? ???	no damage	no damage
Quercus wislizenii	no damage	no damage
Rhamnus alaternus	no damage	no damage
Senecio x 'Sunshine' (S. greyi)	no damage	no damage
Shibatea kumasaca	no damage	no damage
Sophora tetraptera	no damage	defoliated, but releafing throughout
Taiwania cryptomeroides	no damage	no damage
Thamnocalamus spathiflorus	no damage	dead to the ground, but coming back strongly
Thamnocalamus tesselatus	no damage	no damage
Trachycarpus fortunei (x wagnerianus?)	no damage	no damage
Trachycarpus fortunei [Victoria]	no damage	no damage
Trachycarpus latisectus	parts above snow dead, resprouting	parts above ground dead, but growing back again
Tropaeolum ciliatum	died to ground, as it does every year	died to ground, as it does every year
Ugni molinae	20% tip dieback	dead
Umbellularia californica	no damage	no damage
Yushania anceps 'Pitt White'	no damage	no damage
Yushania maling	no damage	no damage

Notable pleasant surprises

I've already noted a number of these in the comments above but here are a few more.

• Araucaria angustifolia was originally planted in August 1998. I was already impressed with it when it lived through December 1998 with only minor tip burn, but this time it was completely unfazed. It is now approaching 20' tall. I think this deserves to be much more widely grown in the Northwest. It lived from 1999 - 2008 and grew more than 6' tall during that time. A. bidwillii, on the other hand, does not really have what it takes to survive in our climate, though I'm not the first person to figure that out.
• Eucalyptus fastigiata is a close relative of E. regnans, yet based on the performance of my plants of both species, I think E. fastigiata is hardier. A relatively small (maybe 20' tall and with a thin trunk) E. fastigiata survived the big freeze, while my giant E. regnans (planted 1999) died. I'm impressed and I think E. fastigiata deserves more experimentation.
• Eucalyptus mannifera subsp. praecox (or just E. praecox according to recent taxanomic changes) is apparently the hardiest subspecies of E. mannifera, a rather tropical looking species with smooth white bark that doesn't grow too large. I knew these were rather hardy but was impressed that this one had only superficial damage.
• Eucalyptus nova-anglica is closely related to the often-tried, yet tender, E. cinerea subsp cinerea; yet it is even more silvery, if such a thing were possible. The brilliant blue-silver color on this one shimmers almost enough to create its own light. And not a speck of damage - wow.
• Lagarostrobos franklinii (formerly known as Dacrydium franklinii) is one of those rare antipodean conifers that is supposed to be tender in our climate. But so far, so good.
• Luma apiculata I thought wasn't supposed to be all that hardy, but it took this freeze like a champion.
• Pittosporum tenuifolium and all hybrids of it generally had no significant damage - it is certainly hardier than given credit for and hardier than most of the other New Zealand Pittosporums. There are so many hybrids out there and of course I can only comment on the few that I have tried - but so far, this group of plants is very promising.

Notable disappointments

• Callistemon x 'Eleanor' was a hybrid (probably a chance seedling) selected for having survived the big freeze of 1998 in a pot at a nursery in Oregon and having attractive deep purple flowers. Unfortunately it turns out to be somewhat inferior in hardiness to some of the reds such as C. subulatus and C. linearis.
• Eucalyptus bicostata is a close relative of E. globulus that grows at much higher altitudes where a winter snowpack accumulates every year, and has beautiful purplish-glaucous juvenile leaves. For how high up it grows in the wild it has been an astounding failure in the Northwest even in moderately severe winters.
• Eucalyptus coccifera, from the highlands of Tasmania, is often referred to in British literature as one of the hardiest species, but I guess it's not - I don't know of any of these still alive in the Olympia area after December 2009. However I do know of one in Sequim that survived 15°F in December 2008 with no visible damage - perhaps drainage is an issue as the Sequim specimen has much better soil drainage.
• Eucalyptus nitens: they're all dead regardless of how great the provenance was. What can I say?
• Eucalyptus youmanii is supposedly one of the hardiest 'stringybark' eucalypts. Not hardy enough though, I guess.
• Fremontodendron is dead across the board, but these may require better drainage to achieve full hardiness.
• Grevillea miqueliana seems like it almost made it - perhaps it would have if they were larger and in full sun. I'm a bit disappointed but I still think this one should be tried again.
• Leptospermum lanigerum - this was a Tasmanian form that I thought would be hardier, oh well.
• Melaleuca squarrosa was another Tasmanian introduction and supposedly one of the hardiest Melaleucas. There may not be any hardy Melaleucas, but one can keep trying.
• Nerium oleander 'Hardy Red' really hasn't managed to perform for me. If I try any more Oleanders it will have to be from some of those new high altitude introductions Europeans have been hoarding over there.
• Phormiums might grow in swamps in New Zealand, but I think good drainage in cultivation improves their ability to handle freezing weather. It would be interesting to do a comparison, although even with better drainage they can have heavy damage when temperatures drop into the teens F.

Eucalyptus results by seed source

Below is a quick list of Eucalyptus species that didn't freeze to the ground in December 2009. This makes it a good starter list of species for further experimenting and trialling in general.

I grew eucalypts from a variety of sources. Two of my favorite sources are Milligan Seeds in New Zealand, and the now defunct Celyn Vale Nurseries (a.k.a. Eucalyptus Nurseries) in Wales. It's a pity Celyn Vale is out of business but Milligan Seeds is still going strong and I recommend them highly as a eucalyptus seed source. I'm glad to have a number of trees in my garden from Celyn Vale seed that may serve as a future seed bank for their hardy provenances. I also have a few good trees from Chiltern Seeds although they are less reliable for cold hardiness. And I obtained some seed from an avid hobbyist who sourced some excellent hardy provenances of various species; these are listed below as "Frank C."

This is far from a perfectly comprehensive study. Ideally I would have tried as many sources as possible for each species, but in some instances I guessed at which source would be more likely to offer a hardier provenance before ordering the seed and never bothered to order it from the other source. Also ideally I would have data on where the seed was originally sourced in the wild. Some trees that would have been interesting to observe in the freeze blew over or died of other causes years ago, including all three of my Celyn Vale E. dalrympleana, and a bluish form of E. stellulata.

The numbers in the list below are my attempt to "score" plants from different seed origins based on their performance. Scores are assigned on a scale of 0 to 10. If it froze to the ground, it gets a 0. If it was undamanged, it gets a 10. Since leaf damage is largely cosmetic, and trees can recover from it quickly without significant setback (for example E. camphora), the idea of "damange" here is based only on the degree of damage to stems/branches. So it may not agree completely with the list above. If more than one specimen of the same species and origin were planted, points are averaged to best represent the performance of that form. Species for which all plants froze to the ground (regardless of origin) are excluded. Hybrids are excluded (although some hybrids are certainly worth trialling).

It's tough to draw any really useful conclusions from such a limited dataset. With more data one might do some averaging of numbers to compare the hardiness of plants from different origins in a more general way. Really I hope this will inspire a more thorough and well-managed study of eucalyptus hardiness, perhaps of the hardiest 30-40 species collected or obtained from several different sources each, somewhere in the Pacific Northwest.

The Future

As I write, climatologists and amateurs alike are prognosticating the "perfect storm" of conditions to produce our coldest winter in decades, including the colder than usual north Pacific, and a very quick transition to the strongest La Niña in decades. Maybe I produced this report too soon! But on the other hand, maybe the next winter or two will provide us with further opportunities for education about plant hardiness in the Pacific Northwest.