Preserving Australian Flora in the Washington Park Arboretum

snow gum forest with blue sky
Laura van Galen
A snow gum forest in Mt. Field National Park in Tasmania

The Pacific Connections Garden (PCG), found at the southern end of the Arboretum, is a place that spurs the floristic imagination. Visitors traverse hemispheres and continents while moseying through gardens that showcase plant communities from specific regions in New Zealand, China, Cascadia, Chile, and Australia. In a short walk it’s possible to pass through our version of the New Zealand high country, continue on to the Cascadia garden, featuring plants native to the Siskiyou mountains, and finish with our representation of the wine palm and monkey puzzle laden temperate rainforests of Southern Chile. A core goal of the Pacific Connections Garden is to present immersive ecogeographic display gardens that create opportunities for people to learn about plants, culture, and conservation simultaneously. Each garden originates with a distinct ‘entry’ or ‘display’ area that serves to exhibit and trial plants native to these countries or regions that show potential horticultural promise for Pacific Northwest gardens. Additionally, there are three well developed Focal Forests featuring plants of known wild origin for New Zealand, Chile, and Cascadia. Pursuant with the goals of the PCG exhibit, the Australian ecogeographic Focal Forest is next to be developed. Hopefully someday in the not too distant future visitors will be able to voyage west from New Zealand, across the Tasman Sea, to find themselves in the subalpine woodland communities of Southeastern Australia, simply by walking east across Arboretum drive!

Long before the inception of the Pacific Connections Garden, careful thought and collaboration was devoted to the continued development of the Australian collection. For the past 85 years the Arboretum has served as a testing ground to trial Australian plants, particularly eucalypts, for their hardiness in our climate. In the footprint of the future Australia Focal Forest you can find a patch of well develop Australian natives planted in 1990, as well as a particularly impressive Eucalyptus gunnii that is 64 years old. While 15 to 20 years ago Australian native plants were not necessarily common in Seattle gardens, they have been steadily creeping into the horticultural consciousness. This increased abundance may in part have been aided by the floriferous and multi-textured PCG displays, as well as by the work of dedicated plant explorers and nurserypeople.

In addition to having an impressive collection of individual Australian specimens, the visionary Curation committee planning PCG sought to represent a complete Australian plant community as the guiding theme of the Focal Forest. To do so they poured over rainfall and temperature data. While there is climatic variation throughout the country, Australia is mostly arid to semi-arid and is the second driest continent after Antarctica. However, there are pockets of rainforest and wetter, colder areas. Areas of Victoria and New South Wales, in the south eastern part of the country, specifically the Australian Alps, as well as mountainous parts of the island state Tasmania, have precipitation and cool temperatures similar to those of the Pacific Northwest. The curation committee seized upon a specific type of Eucalyptus plant community that occurs in the Snowy Mountains as particularly emblematic—the striking snow gum (Eucalyptus pauciflora ssp. niphophila) and associated woodland. While I have not had the chance to visit a snow gum woodland, I have read a description comparing it to an alpine version of our Oak Savannah (but I imagine it would be odd, blue hued, and more Gondwanan leaning, also).

Plans are in motion, and much work has already been done for the next phase in expanding the Australian Focal Forest. Over the past two years several cedar trees and a few duplicates of collection trees were removed to open the canopy for new plantings. (The trunks from these removals did not go to waste—wood chips were used to mulch garden beds throughout the Arboretum and other logs repurposed, with some of the wood being milled to make the ornamental base for the Arboretum foundation’s Northwest Flower and Garden Festival display garden). Additionally, earlier this spring and winter a dedicated group known to some as the ‘Monday Volunteers’ made great progress removing invasive species like English ivy and Himalayan blackberry from the future footprint, paving the way for bigger changes to come. This fall several examples of eucalyptus native to the “focal” area will be planted along with companion shrubs. Be sure to look out for developments in this part of the park!

Cindy Clark
Eucalyptus gunnii

In the meantime, you can revel in the Australian Entry Gardens. Constructed in 2008 the original entry garden (located across Arboretum drive from the PCG meadow) was the first major installment of Australian plants to the arboretum and is likely one of the most well established outdoor displays devoted to the flora of Australia this far north. In June 2019 a second entry garden was developed. Here a large planting of over 130 plants comprising 23 different species and cultivars installed within and around the bus turn-around. The plants in this expanded entry garden have settled in well after the relatively warm winter, and the Grevillea, Callistemon and Eucalyptus species have been particularly strong growing.

The most notable trees in the original entry garden are a snow gum planted in 2008 and a spinning gum (Eucalyptus perriniana), an associated eucalypt species, planted in 2011. Both trees have quite a diagonal tilt to them due to former lack of morning sun, but hopefully the newly increased light levels in the area will encourage some gnarly twisting, turning, lifting, and eventual straightening out of these trees. Some other noteworthy plants include a wide variety of Grevillea species and cultivars, leatherwoods (Eucryphia spp.), mountain plum pine (Podocarpus lawrencei), alpine tea tree (Leptospermum rupestre), celerytop pine (Phyllocladus aspleniifolius), river lomatia (Lomatia myricoides), Tasmanian pepper berry (Tasmannia (syn. Drimys) lanceolata, among others.

grevillea covered in snow
Grevillea victoriae ‘Marshall Olbricht’

Such an opportunity to delight in and learn about plants from Australia is especially poignant in light of the recent wildfires which ravaged large swaths of the country this year. When browsing the collection, it is important consider these tragic events, as the opportunity to make relatable seemingly distant experiences is part of the great power of an ecogeographic garden.

Fire is a natural part of Australian ecosystems, so much so that some native plants actually require it to produce offspring. However, fire frequency and intensity has been trending upwards. This year Australia endured it’s hottest and driest seasonal conditions, and subsequently the most destructive bushfire season on record. These fires caused huge loss of life and property and will undoubtedly have severe ecological consequences. Even those fire obligate plant species cannot withstand fire events at this scale and intensity. The sheer amount of land that burned in Australia in 2019 and 2020 is hard to fathom. To put things in dreadful perspective, fires raged through more than 31 million acres of the Australian continent, leaving burned areas amounting roughly to the size of the UK. These horrific fires impacted every Australian state, with the southeastern region of Australia most severely affected with 13 million acres burned.

snow gum forest with blue sky
Laura van Galen
A snow gum forest in Mt. Field National Park in Tasmania

The effects of climate change in concert with variable weather conditions have created an altered fire regime that the Australian flora and fauna (humans included!) are not adapted to. The problem is both spatial and temporal. Fire events that had been patchy in the past are now raging through entire ecosystems. This has a devastating impact on wildlife, likely pushing some species to extinction. For instance, small marsupials who in the past could have taken refuge from fires have had the entirety of their native ranges destroyed all at once. Forests that require fire and heat to regenerate are experiencing fires so hot that the oldest, largest, and normally resistant, seed producing trees are being destroyed. The increased frequency of fire events suggests an increased likelihood that forests already regenerating from fire may experience another destructive fire event before they have recovered. If fires destroy all seed producing trees, and then more fires burn the vulnerable immature trees that are regenerating from previous fires, there will be no reproductively mature trees contributing to the seed bank and forests will cease to recover at all. The recent fires in Australia have permanently changed the trajectory of the landscape there.

Such tragic events emphasize the relevance of conserving and celebrating the Australian plants here at the UWBG. Snowgum woodland communities are among those in greatest peril. While they can withstand fires of certain intensity, they do not require fire to grow new seedlings. Indeed, ongoing research conducted prior to 2019 suggests these woodlands have been negatively impacted by burns that occurred in 1998, 2002, 2006, and 2013. The situation in Australia highlights the impermanence and volatility of the natural world. It is undeniable that climate change will have an impact on landscapes worldwide, and there is no time like the present to push forward in developing these unique transpacific ecogeographic gardens! Speaking more broadly, in this time of zoom calls and virtual hangouts, the power of an ecogeographic garden to transport and provide shared experience and understanding is all the more bittersweet. Nevertheless, to hold us over for now and perhaps inspire some home gardening ideas, below is a list of some particularly fabulous Australian plants you can find at the Washington Park Arboretum. G’day mate!

Leptospermum grandiflorum: A small tree evergreen in the Eucalyptus family with silver leaves and papery bark. A close relative to New Zealand’s cherished manuka, Leptospermum scoparium. Grows to about 10 feet with a fairly columnar form, appreciates summer water.

 

close up of grevillea leaves
Grevillea gaudichaudii

Grevillea gaudichaudii: A prostrate or mounding Grevillea with striking lobed leaves. It is a naturally occurring hybrid between G. acanthifolia and G. laurifolia that occurs in the Australian alps. To read more about this Grevillea and others check out the January 2019 Plant Profile by Roy Farrow.

blue green leaf-like branches
Phyllocladus aspleniifolius

Phyllocladus aspleniifolius: An unusual conifer (especially to us, and perhaps to everyone). What appear to be glaucous leathery leaves are actually glaucous leathery phylloclades- essentially flattened branches functioning as leaves. The genus is mostly confined to the southern hemisphere and found in New Zealand, Tasmania, and Malesia. P. aspleniiflolius is endemic to Tasmania. It thrives in dry lean soils and has N-fixing bacteria in its root nodules!

Billardiera longiflora: An evergreen vine with large blue fruit, need I say more! Native to the moist shady forests of southern Tasmania. The two plants in the Australia entry garden are thriving, one mounding on the ground and another propped up on a Callistemon.

Podocarpus nivalis ‘Red Tip’: A useful little low growing podocarp, even does well in a container. New growth is red, hence name of the cultivar. This plant is heavily featured in the entry gardens, and its wild counterpart is a key part component of snowgum woodlands.

Prostanthera cuneata: Alpine mint bush, a real cutie. It is a compact evergreen shrub with teeny mint scented leaves and white flowers in late summer.