My Stroll Through Azalea Way

Yesterday, I went for a stroll through through Azalea Way in the Washington Arboretum, a gravel path lined by cherries, azaleas, rhododendrons, and many other beautiful flowers, shrubs, and trees. Azalea Way has a long and storied history – it was first created by the Puget Mill Company in the late 19th century to transport timber to Lake Washington. In 1900, the area we now know as the Arboretum was incorporated by the city of Seattle as “Washington Park,” and Azalea Way was developed into the “Speedway,” a 3/4-mile race track used by local horse owners. In 1903, the Olmstead Brothers Landscape Architects Firm designed Lake Washington Boulevard’s sprawling path through Washington Park, but the park remained relatively undeveloped through the 1920s.

However, there was a burgeoning interest in creating an official Arboretum for the city of Seattle during this time, headed by faculty members at the University of Washington. In 1934, the Arboretum was officially established in Washington Park, the Olmstead Brothers were again hired in 1936 to help design the arboretum, and in 1939, the first cherry blossoms, rhododendrons, and azaleas were planted along the “Speedway” that we now know as Azalea Way. With the Great Depression crippling the nation’s economy, the development of the arboretum was provisioned by FDR’s Work’s Progress Administration. In this way, you could say the Arboretum was one of the first “Green New Deal” projects!

During the post-World War II economic expansion of the 50s and 60s, the arboretum and Azalea Way continued to grow under director Brian Mulligan, an Englishman who made his name growing “Victory Gardens,” – gardens that produced food to help support the war effort – at Royal Air Force stations throughout Great Britain. Mulligan placed an emphasis on correctly siting certain species to areas well-suited for their growth, and the arboretum has thrived as a result.

I’m not sure if the two below photos are the same location – I’ll have to go see if I can find the 1957 location the next time I’m taking a walk! But they sure look similar.

 

Phenology

In addition to having a passion for meteorology, I am interested in phenology, which is the study of the relationship between seasonal plant/animal patterns/behaviors and the climate. During spring, I like to track the timing of our flowering trees, and during late summer and autumn, I like to track fish counts as salmon make their way upstream to spawn after the first heavy rain in autumn, with the rain bringing swifter and cooler rivers and increasing chances of salmon survival as they make their long, difficult trek upstream. One of the major issues dams pose to fish survival is that they interfere with the phenology of fish migration, as the reservoirs behind the dams store heat and cause river temperatures to peak later in the season – right when salmon have evolved to migrate back up the rivers and spawn.

Natural and anthropogenic climate change has also had a significant influence on phenology. In the mid 1800s, Henry David Thoreau, the great American naturalist and writer, took detailed observations of plant and animal life in Concord. A paper by Polgar, Gallinat, and Primack (2013) found that woody species were leafing out, on average, a full 18 days earlier than they did in the 1850s. That’s a massive phenological shift, but then again, we’ve experienced a massive shift in climate over the 170 years, from moving out of the Little Ice Age into the era of anthropogenic global warming, with continued, accelerating warming expected through the rest of the century.

But even though plants are blooming earlier on average in most parts of the world, there’s still a large amount of year-to-year variability. Here in the Pacific Northwest, the timing and intensity of our spring blooms are heavily dependent on the weather from late January through late March, although November and December can have a notable impact if they were anomalously wet or dry, particularly for some of the earliest-blooming plants. As one might expect, the cooler and cloudier the period preceding the bloom, the later the flowering tends to be compared to average, and vise versa, with the timing varying as much as 2 weeks from average on either side for many of our plants. Spring 2011 was an example of a spring with a very late bloom (due to cool/wet weather courtesy of a strong La Nina), while Spring 2015 had a much earlier bloom due to the exceptionally warm 2014-2015 winter, which featured the “Blob” of warmer-than-average sea-surface-temperatures off our coast that has yet to be matched.

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Azalea Way

Though azaleas are its namesake, azalea way is perhaps most famous for its cherry blossoms. Cherry blossoms are from the Rosaceae family, a medium-sized, diverse family of flowering plants with nearly 5,000 known species. It includes pomes (like apples and pears), drupes (like peaches and cherries), many berries, and several flowering shrubs, including its namesake – the rose. All feature pentamerism (5-sided symmetry), which is a very common feature among all flowering plants.

Echinoderms, such as sea stars and sea urchins, are the only animals with pentamerism. Note the similarities!

The flowers of the pomes and drupes in Rosaceae are very similar and can be easily confused. Plum trees are the first to bloom and have white flowers, and I’ve seen many of them currently blooming around the city. There were a couple of Okame Cherry Blossoms along Azalea Way in full bloom, which can be distinguished from other cherry blossoms by their bright pink flowers and the fact that the reach full bloom about 3 weeks earlier than the Yoshino Cherry trees that dot Azalea Way and line the UW Quad.

Most of the Yoshino cherry blossoms along Azalea Way had not yet bloomed, but there were a couple that were beginning to flower. The Yoshino cherry blossoms peak in late March, and Azalea Way, the UW Quad, Seward Park, and the Japanese Garden in the Arboretum are just a few of the places in the city you can see them. The 30 Yoshino cherry trees in the UW quad were actually moved from the Arboretum onto campus in 1975, and they were planted in 1936, making them nearly 90 years old and at the tail end of their life expectancy. They likely have a few more years in them, but they certainly aren’t immortal.

Pomes such as apples and pears have whiter, less dense showy blossoms than the drupes, they should start to bloom in the next couple weeks, likely reaching peak bloom by early April.

The daffodils were a brilliant yellow and were definitely in peak bloom.

Arboretum Drive E

I also walked along Arboretum Drive E, which is surrounded by tall conifers and sees less sun than Azalea Way but still has plenty of flowering trees. Although most rhododendrons and azaleas were a long ways from blooming, a couple in “Rhododendron Glen” near the Drive were already beginning to show their colors. There are so many varieties of rhododendrons and azaleas that they can bloom from March all the way through May or even June, and their flowers tend to last for a longer time than other flowering trees, in my experience.

The magnolias were not yet in bloom, but their buds were just about to burst.

The drive was also lined by a smattering of camelias and stewartias. Both are part of the Camelia family, but stewartias can be distinguished by having five large, radially symmetric flowers, while camelias have 1-2 additional “layers” of flowers behind these front five, giving camelias a “fuller” appearance.

After dry but relatively cool weather this week, we should see a more typical early spring La Nina pattern this weekend and next week, with slightly above-average precipitation and near-normal temperatures. Combined with the relatively seasonable weather we’ve had thus far in 2022, the timing of blooms for the next several weeks should align well with our long-term averages.

Wherever you live, make time to stroll through the woods over the next few weeks – the rebirth of spring in the Pacific Northwest is a sight to behold.

Azalea Way/Arboretum History – Sources used:

• Azalea Way. University of Washington Botanic Gardens. (1970, March 14). Retrieved March 7, 2022, from https://botanicgardens.uw.edu/washington-park-arboretum/gardens/azalea-way/
• Core Collections. University of Washington Botanic Gardens. (1970, March 14). Retrieved March 7, 2022, from https://botanicgardens.uw.edu/washington-park-arboretum/plants/core-collections/
• Horses, cars, & guns: Sport in the arboretum. Elisabeth C. Miller Library. (n.d.). Retrieved March 7, 2022, from https://depts.washington.edu/hortlib/hours-and-contacts/history/wpa-history/horses-cars-guns/
• Long, P. (2001, August 9). Seattle’s Washington Park Arboretum. HistoryLink. Retrieved March 7, 2022, from https://www.historylink.org/File/3490
• Your gain would be our loss: Brian O. Mulligan. Elisabeth C. Miller Library. (n.d.). Retrieved March 7, 2022, from https://depts.washington.edu/hortlib/hours-and-contacts/history/wpa-history/your-gain/