[April 6] UPDATE: Flower petals are falling on the Quad as the trees lose their blossoms. The waning bloom is still quite a site but it’ll be a while before the trees are back on full display.

[March 23] UPDATE: The cherry trees are officially in peak bloom! Visit campus anytime in the next week or so to see the blossoms in all their glory.

[March 18] UPDATE: Recent temperature swings have slowed bud development for the Quad cherries. About half of the trees are still in peduncle elongation stage while half have moved on to the “puffy white” stage that precedes full bloom. Cool temperatures in the coming days may delay peak bloom as trees gradually blossom. Warm weather could produce a sudden transition. Check the live cams for updates.

[March 13] UPDATE: It’s snowing but the blossoms are still growing! The Quad cherries are now in the “peduncle elongation” stage, where the flower-bearing stalk extends from the bud. Some have also begun to flower.

Each spring, large crowds gather on the 天美影视传媒 Quad to admire 29 puffy pink cherry trees making their seasonal debut. The trees begin to wake up as the weather warms, and this year, estimates suggest that they will reach “peak bloom” on March 20.

The UW’s iconic cherry trees achieve peak bloom when 70% of the blossoms have opened, but the week before and after still offer visitors an optimal viewing experience.

The cherry blossom visitors’ website provides updates on bloom status as well as details on transportation, activities and amenities. The cherry blossoms also have live video feeds for virtual viewing and their own social media accounts on and .

The cherry trees are both beautiful and ecologically significant. Tracking when the buds burst each year helps researchers predict peak bloom and determine how climate warming is impacting the trees, which were planted in the Washington Park Arboretum in 1936 and then relocated to UW in 1962.

This year, many plants began to emerge early as a mild winter gave way to spring. Recent UW research described how plants rely on both temperature and light cues to time their flowering. Temperature is particularly important to cherry trees, which estimate the arrival of spring based on how cold it has been. They accrue “chilling units” as winter progresses and “heating units” as it yields to spring.

“The buds need to accumulate a specific amount of chilling units before they can start accumulating the heating units. When it is not as cold, the chilling units accumulate much slower, so it takes them longer to wake up from dormancy, which is very counterintuitive,” said , a UW doctoral student of environmental and forest sciences.

Theil is now overseeing data collection on campus, with the help of approximately 20 undergraduate students. The researchers make observations as the trees begin to wake up and feed the data into a computer model that incorporates weather forecasts to predict peak bloom.

Historically, the onset of peak bloom has fallen between March 12 and April 3, with an average date of March 23. While the weather impacts peak bloom year to year, climate change drives longer term trends over multiple decades.

Research shows that bloom time has shifted approximately two days earlier each decade since the 1960s. Researchers began monitoring the trees in 2012 and referenced newspaper archives to estimate peak bloom dates for the preceding years.

“With the climate warming more rapidly in the spring, I expected to see the flowers blooming earlier,” said lead author , a recent doctoral graduate from the UW school of environmental and forest sciences. “But as we dove into the literature and examined the data, we saw a delay in bloom, as a result of winter warming in Seattle.”

The study focused on the Somei-yoshino, or Yoshino, cherry tree cultivar. These trees, sometimes called the Japanese flowering cherry, are found throughout Japan. They also line the National Mall in Washington D.C. and paint many Seattle neighborhoods pink in the springtime.

The bloom delay Maust observed applies only to Yoshino cherry trees in Seattle. In colder climates, such as Washington D.C., the trees have ample time to accrue chilling units. Still, the two populations are quite similar, genetically.

Propagation, or breeding more trees, occurs by grafting one tree onto another. This process limits genetic variability in favor of consistency. Because all Yoshino cherry trees are sterile clones of one another, they do not produce fruits or seeds, but they do reliably bloom in beautiful pink hues each spring.

For more information on bloom time, contact Theil at mtheil@uw.edu or Maust at? amaust@uw.edu. For information about the Yoshino Genome Project, contact Steinbrenner at astein10@uw.edu.

[April 4] UPDATE:? Our iconic cherry trees are in bloom. Plan your visit to campus using this map, which highlights the locations of different cherry trees on the 天美影视传媒 campus, including the Yoshino blossoms in the Quad.

[March 31] UPDATE: The majority of the blossoms are in peak bloom, a developmental phase which usually lasts about 10 days.? This phase can last longer if the weather is cool, calm and dry.

[March 25] UPDATE:? There are three developmental phases currently visible on the UW cherry trees. The majority of the blossoms are in the “peduncle elongation” phase where the stem is formed and the petals have begun to develop. Many blossoms are in the “puffy white” phase, when the fully formed flowers that are ready to open do so with increased sunshine, warmth and clear skies. Approximately 20% of the flowers in The Quad are in bloom.

[March 24] UPDATE:? This week’s warm weather in Western Washington will help the UW’s famous cherry tree blossoms open. The trees have entered what scientists call the “puffy white” stage, the final phase before blooming.?

[March 18] UPDATE: The cherry blossoms in The Quad are now in the “peduncle elongation” stage, which is when the stalks supporting the flower protrude from the bud.

The 天美影视传媒 invites the community to enjoy the iconic Quad cherry blossoms on campus this spring. The 29 cherry trees in the 天美影视传媒 Quad usually draw large crowds on campus and reach peak bloom the third week of March, and this year is on track to meet that timing.?

Warmer temperatures and mild weather affect when the cherry trees start to blossom and when they reach peak bloom.? The UW’s Bloom Watch is updated regularly to reflect the current blossom phases, including when peak bloom is expected.

The UW’s iconic Yoshino cherry trees typically bloom March through April, but forecasting the precise dates for prospective visitors is an annual challenge. To refine the prediction, a UW research group is using historical weather data going back to 1966 and student-collected observational data to come up with the timing of peak bloom — and looking at how a warming climate impacts that date. Once the trees reach peak bloom — when at least 70% of the blossoms have emerged — cooler temperatures, dry weather and low wind will keep the blossoms on the trees longer.?

“We found that in Seattle, because our winters are so mild and warm, there’s actually been a delay in the bloom time over the past six decades,” said Autumn Maust, a UW doctoral student in the School of Environmental and Forest Sciences. “The bloom time is shifting a little bit later.”

This is because cherry trees need to accumulate both chilling and warming units — accrued over springtime periods of cool and warm temperatures — to reach a threshold that forces them through the bloom stages. Mild winters, Maust says, mean it takes longer to reach the required chilling units.?

There are dozens of varieties of blossoming cherry and plum trees across the Seattle area, with blooms for some species visible from early February until May. Bloom colors range from white to light rose to dark pink, and cherry trees — unlike plums — have distinct horizontal-line patterns on their bark called . These help the trees “exhale” or release carbon dioxide and water.

But you need not wait for peak bloom to visit campus, the season is underway. The UW maintains a visitors’ website dedicated to updates on the status of the blooms as well as details on transportation, activities and amenities. The Quad cherry blossoms also have their own social media accounts on and . Cherry tree enthusiasts who can’t make the trip can keep up with UW Video’s live webcam overlooking the Quad, a?virtual tour?with photos from campus and tweets from .?

###

For more information or to schedule an interview, please contact Dana Robinson Slote: drslote@uw.edu or 206.457.6058

[March 26 update: Peak bloom is set to continue at least through the weekend of March 30-31, according to UW arborist Sara Shores. “The cool weather is helping now,” said Shores. “I believe the blooms will be hanging on into the weekend. The leaves are close and once the leaves begin [to emerge], the blooms are harder to see.”]

[March 20 update: As peak bloom continues, this post was updated to include a video about an ongoing study of the UW cherry trees and the headline was changed from “UW cherry blossoms set for peak bloom in late March” to “Video: Predicting cherry tree bloom timing at the UW”]

[March 19 update: Cherry trees in the UW Quad are at approximately 70% bloom and have entered “peak bloom” stage. “If the weather stays cool, with little wind or rain, the bloom should last about two weeks,” said Autumn Maust, a UW doctoral student in environmental and forest sciences.]

[March 18 update: Thanks to unseasonably warm weather over the weekend, approximately 50-60% of buds on the UW Quad cherry trees are now in bloom, with peak bloom expected to begin by March 19 at the latest.]

[March 15 update:?All trees in the Quad now have pink buds with some florets visible. Approximately 2% of buds on the UW Quad cherry trees are now in bloom.]

[March 13 update: All cherry trees in the Quad are now at the “peduncle elongation” stage of bud development, during which the stalks supporting the florets grow longer. It is one of the last stages before the florets open.]

Cherry trees on the 天美影视传媒’s Seattle campus are waking up and getting ready to say hello. For the 29 iconic Yoshino cherry trees in the UW Quad, peak bloom will likely begin after March 20, according to UW arborist Sara Shores.

“Historically, peak bloom in the Quad typically begins during the third full week of March and goes into the fourth week of March. That seems to be what this year is going to look like,” said Shores. “Right now, I would guess that the last two weekends of March are ideal viewing conditions.”

This post will be updated with the latest estimates, which could change based on weather conditions.

Cherry tree fans don’t have to wait for peak bloom to visit campus. The entire cherry blossom season is a great time to visit and see the trees in bloom.? The UW maintains a visitors’ website dedicated to the school’s cherry blossoms, providing tips for getting to campus and maximizing the tree-viewing experience. The site has updates on the status of the blooms as well as details on transportation, activities and amenities. The Quad cherry blossoms also have their own social media accounts on and , formerly Twitter. For cherry tree enthusiasts who can’t make the trip, campus webcams are a good option for virtual viewing.

The timing for peak bloom — meaning 70% of buds have emerged — varies each year based on weather conditions that the developing buds are exposed to in January, February and March.

“In order to reach peak bloom, buds need to accumulate a certain number of both cold and warm days, known as ‘growing degree days,’” said Marlee Theil, a UW graduate student in the School of Environmental and Forest Sciences.

As of March 8, just over half of the cherry trees in the Quad were at the “peduncle elongation” stage of bud development, during which the stalks supporting the florets grow longer. It is one of the last stages before the florets open and the bloom season begins. The remaining cherry trees in the Quad are also progressing normally, albeit one or two days behind.

Since 2018, a UW research group has been?monitoring campus blossoms?from January to April with the goal of creating a model that will use weather data to predict the timing of peak bloom. Theil currently leads the monitoring team of more than 20 undergraduates.

“The data that we gather will not just help us know in future years when to come to campus to enjoy the trees,” said Theil. “This will also be a valuable research tool to understand how these trees respond to changing environmental conditions.”

There are more than 100 cherry trees on campus. The main species is Yoshino, including the trees in the Quad. Other varieties include the Higan, Hisakura, Kwanzan, Mt. Fuji and Shirofugen trees that can be viewed at?locations across campus. The Yoshino trees bloom earlier than many of the other species.

“Even as bloom season wanes for the Yoshino trees in early April, other trees on campus will be starting,” said Shores.

How long blossoms will remain on the trees this year depends on the weather. Cooler temperatures, less rain and lighter winds all will help keep blossoms on the trees.

For those who wish to avoid crowds on the Quad, visiting on weekdays and in the early mornings are better options. The UW asks that visitors not climb the trees, move their branches or shake their branches, as this can cause damage.

Visitors are encouraged to share their photos by using the??hashtag.

For media inquiries about the cherry trees, contact James Urton at jurton@uw.edu or 206-543-2580. For broadcast media, and from past years are available.

[April 5 update: The cherry trees in the UW Quad have reached 100% bloom, where all buds have erupted with petals.]

[April 3 update: Approximately 90% of the buds in the UW Quad have bloomed. Cooler weather will help preserve the blossoms, though heavy rain or wind will knock off petals. UW arborists estimate the trees will remain above 80% bloom through the weekend of April 8-9.]

[March 31 update: The trees in the UW Quad have surpassed 70% bloom, so they have reached “peak bloom.”]

[March 29 update: The UW Quad cherry trees are at 50% bloom, and are on track to reach peak bloom this weekend.]

[March 27 update: The cherry trees in the UW Quad are now at an estimated 25% bloom, and rapidly increasing with the warmer weather.]

[March 21 update: The trees now have pink buds with some florets visible. An estimated 5% of buds on the UW Quad cherry trees are now in bloom.]

The cherry blossoms at the 天美影视传媒 campus are a seasonal tradition and celebration for the entire region. This year’s colder-than-usual spring is demanding a little more patience. Mark your calendars and plan your visit for a peak bloom expected in early April.

“The cold snap has delayed the blooms slightly, but I don’t anticipate any damage to the blossoms as a result of the cold weather,” said , the UW campus arborist.

As of March 15, the cherry trees in the UW Quad are mostly green buds and a few florets, where the folded-up petals are emerging. The trees will likely hit 10% bloom, meaning one in every 10 buds has erupted in pink or white blossoms, the week of March 20. Shores estimates that the trees will reach peak bloom — when 70% of the buds have emerged — in early April. This post will be updated with the latest estimates.

A dedicated to the UW cherry blossoms provides tips for coming to campus and for maximizing the tree-viewing experience. The site has updates on the current status of the blooms as well as details on transportation, activities, amenities, nearby food options and even new cherry-themed merchandise.

Those who prefer to avoid crowds may want to visit the Quad on weekdays and in the early mornings. Others may appreciate being around fellow cherry-blossom aficionados, especially after the quieter years of 2020 and 2021 due to pandemic restrictions.

The main species of cherry tree on the UW campus is Yoshino, including the 29 iconic trees in the Quad. Other varieties include the Higan, Hisakura, Kwanzan, Mt. Fuji and Shirofugen trees that can be viewed at locations across campus.

A UW research group has been monitoring campus blossoms from January to April since 2018 with the goal of creating a model that will use weather data to predict the timing of peak bloom. Autumn Maust, a UW doctoral student in environmental and forest sciences, currently leads the 14 undergraduates on the monitoring team.

“I personally enjoy strolling through the Quad during peak bloom in the evening,” Maust said. “There is typically less foot traffic, and seeing the trees lit up at night is very peaceful.”

How long blossoms will remain on the trees this year depends on the weather. Cooler temperatures, less rain and lighter winds all will help keep blossoms on the trees. The university asks that visitors not climb the trees or shake their branches, as this can cause damage.

Visitors are encouraged to share their photos by using the hashtag.

For media questions about the cherry trees, contact Hannah Hickey at hickeyh@uw.edu. Broadcast media: is available for download. are also available.

4/1/22 update: Traffic congestion on campus is significant during cherry blossoms season and parking is limited. Please take light rail to the University District Station or park in the or .

The 29 cherry trees in the Quad usually reach peak bloom the third week of March, said UW arborist , and this year is on track to meet that timing. Warmer temperatures and mild weather all factor into when the cherry trees start to blossom and when they reach peak bloom.

Virtual viewing options are also available, including UW Video’s live webcam overlooking the Quad, a?virtual tour?with photos from campus and tweets from . Hear Shores explain how a cherry tree functions in this interactive “anatomy of a cherry tree” illustration:

Once the trees reach peak bloom — when at least 70% of the blossoms have emerged — cooler temperatures, drier weather and lighter winds will keep the blossoms on the trees longer. The university asks that visitors not climb the trees or shake their branches, as this can cause damage.

Dozens of varieties of blossoming cherry and plum trees can be found across the Seattle area, with blooms visible from early February until, for some species, May. Petal colors range from white to light rose to dark pink, and cherry trees — unlike plums — have distinct horizontal-line patterns on their bark called . These help the trees “exhale” or release carbon dioxide and water.

Plum trees, which often are mistaken for cherry trees, bloom earlier than most cherries and don’t have lenticels on their bark.

The Seattle Department of Transportation maintains this of trees across the city. To see cherry trees in your neighborhood, click on “Explore street trees” in the top navigation bar, then click on “trees by type” and look for trees with the “Prunus” genus (cherry and plum trees).

For more information on the UW campus cherry blossoms, contact Michelle Ma at mcma@uw.edu.

Viewing options

A number of virtual viewing options are available, including UW Video’s live webcam overlooking the Quad, a?virtual tour with photos from campus that will be updated throughout the blooming season and tweets from .

live webcam
Virtual tour

UW News will not track full bloom timing this year due to the pandemic. Please avoid coming to campus to see the cherry blossoms and instead enjoy them virtually. Campus buildings along the Quad are closed to the public and restrooms are not available.

Identifying cherry blossoms

Many of the earliest-flowering pink trees each spring are plums, Shores said. She recommends checking the bark to verify. Plum flowers also tend to smell sweeter than cherry flowers.

Find cherry blossoms in your neighborhood

The Seattle Department of Transportation maintains this of trees across the city. To see cherry trees in your neighborhood, click on “Explore street trees” in the top navigation bar, then click on “trees by type” and look for trees with the “Prunus” genus (cherry and plum trees).

Virtually tour the blossoms on campus

These jobs clearly include the university’s extraordinary medical, facilities, custodial and housing staffs. But another role that’s often not seen is the work of our campus photographers. They continue to capture the visual stories and people on campus in a time when many of us aren’t there to see them ourselves.

UW News asked one of our campus photographers, Dennis Wise, to share some of his favorite photos he’s taken this spring, and to describe what it’s like working on campus now.

“It has been two very different campuses these past few months,” Wise said. “From one perspective, it is an incredibly busy and exciting campus from the work in the UW Medicine facilities and the student volunteers in every place I’ve visited, to employees sewing masks and the 60-plus volunteers at the UW Virology Lab doing COVID-19 testing.”

But, he said, there’s another side to campus as well.

“From another perspective, it is quiet and empty. Red Square is deserted and no one is walking through the Quad — even the buses are empty,” he said.

Overall, Wise said he has been inspired by the people he’s been able to photograph over the last several months.

“I’ve been overwhelmed by the faculty, student and staff members’ passion, caring and devotion to the UW’s mission to be the best university in the world as measured by impact,” he said.

The work of the UW’s campus photographers also captures how quickly life has evolved during this pandemic — from the early guidance of emphasizing hand washing and using disinfectant, to maintaining appropriate distancing and, most recently, wearing masks in public.

Here are some of Wise’s favorite photos from this spring — which highlight both the beauty of campus and the work of the university’s staff, faculty and students.

There are several options to enjoy the blossoms virtually this year: UW Video’s live webcam | Facebook photo album | UW Video’s Aerial footage| Follow on Twitter

UW Video’s live blossom camera

In case the video above is unavailable, check out UW Video’s page here.

Facebook album

Aerial footage

ORIGINAL POST on March 5: A relatively mild winter in the Seattle area means the iconic cherry trees in the 天美影视传媒 Quad are on track for a typical bloom season.

The trees likely will reach peak bloom in late March, said , a UW doctoral student in the School of Environmental and Forest Sciences who leads a team of undergraduates collecting data on bloom timing.

The buds appear to be progressing a few days ahead of last year’s timing, Bradshaw said, according to the data that students have been collecting since early February. Warmer temperatures and sunlight usually influence bloom timing each year.

Once the trees reach peak bloom — when at least 70% of the blossoms have emerged — cooler temperatures, dry weather and low wind will keep the blossoms on the trees longer, he explained.

The cherry trees in the Quad, “Somei-yoshino,” are particularly striking when they reach full bloom because unlike many other flowering tree species, their white-pink blossoms take center stage before the leaves start filling in.

“Something that’s really special about these trees compared with other cherry trees is they bloom before their leaves are out, and that’s such a beautiful thing to see,” said Bradshaw, who also works as a pest management coordinator with the UW’s grounds maintenance team. “It’s amazing to see these massive trees with only their blooms out.”

The 29 large cherry trees in the Quad are about 87 years old and healthy, said campus arborist Sara Shores.

The Quad cherry trees were originally planted on arboretum land near Montlake Boulevard where Highway 520 passes through. They were moved to campus in 1962 when the highway’s construction required the trees to be relocated. These details, as well as more history on the cherry trees, are described in a recent??written by Yuki Shiotani, a student at Waseda University in Tokyo who studied at the UW as an exchange student.

This is the second year that Bradshaw has enlisted the help of about 10 undergraduate students to collect data on bloom timing for the 118 cherry trees across campus, including the Quad trees. The students visit each tree at least twice a week on average, taking photos and noting which of the five bloom stages the trees appear to be in, and how much of that stage is complete.

The goal is to gather enough data year after year to build a model that will help predict peak bloom timing, similar to the success Washington, D.C. has had with its model.

“We’re hoping to better track when they will bloom, and in the future align our data with weather data to be able to answer how much temperature and weather are dictating when they bloom,” Bradshaw said.

Each spring, thousands of visitors flock to the 天美影视传媒 campus to see the iconic cherry trees in the Quad. Class discussions, casual Frisbee tosses, lunchtime picnics and even wedding portraits all take place under the beautiful blossoms, which typically?hit their prime in late March or early April. This year, they reached peak bloom on March 29.

But there’s no easy way to predict when peak bloom will occur each year for the trees in the Quad. Every spring, UW Facilities staff diligently check on the blossoms as they progress, but it’s hard to say down to the day, or even week, when the blossoms will be at their best. In contrast, peak bloom periods for Washington, D.C.’s impressive cherry trees with reasonable accuracy, thanks to years of meticulous data collection and models linking the historical bloom data with temperature, such as the one developed by UW professor .

Now, a team of UW students hopes to make it possible to accurately predict peak bloom timing for the Quad cherry trees. Led by , a doctoral student in the School of Environmental and Forest Sciences, 10 undergraduate students are documenting bloom information on all 118 cherry trees across campus, including the 29 Quad trees.

“We started this project to collect data on trees to predict more accurately when they will bloom, and also to see how climate change is affecting bloom times,” said Bradshaw, who began collecting data on a handful of trees by himself last season. This year, he enlisted the help of other students, who each are responsible for a block of trees around campus.

Collectively, the students visit every cherry tree on campus at least twice a week on average, sometimes swinging by after class or, in the case of one data gatherer, taking a break on his runs. On each visit, the students take two photos — one that shows the full tree, and another close-up shot of a cluster of buds. They also note which of the five bloom stages the tree appears to be in, and how much of that stage is complete. Tree names and dates are filled in automatically in a smartphone app they use to collect the data.

Favorable temperatures and day length are the two most important factors that determine when plants will reach full bloom, including cherry trees. Cherry tree species bloom at different times, and blossoms usually stay on the trees for two or three weeks if wind is low and temperatures are cool.

For freshman TJ VanderYacht, pausing his run two or three times a week to visit the cherry trees near Husky Stadium is a way to dive into fieldwork early in his time at the UW. VanderYacht, who grew up in Washington, said the cherry trees are famously tied to the UW, a quintessential part of campus.

“I thought it’d be a great way to get involved with my school and the day-to-day research going on here,” he said. “It’s a good opportunity to be part of something that characterizes the UW.”

UW senior Rachel Liu heard about the cherry blossom project and wanted to get involved to practice computer-aided mapping skills, which she is learning simultaneously in a class she is taking this quarter. Liu, who is in charge of the trees along Rainier Vista and half of the Quad, said she stops by after class, usually spending up to an hour three times a week noting details about the trees.

“I thought, wow, this is such a great opportunity to practice these skills,” said Liu, who is majoring in biology. “I’m really interested in plant biology, and I’m hoping to do research after I graduate related to plants or maybe fungi. It’s great to get the experience of collecting data.”

Data collection for the UW trees, while just beginning, is already more robust than the efforts for D.C.’s cherry blossoms, said Bradshaw, who compared notes with the National Park Service that the capitol’s blooms. It might take several years of consistent data gathering for the UW trees, but Bradshaw hopes that patterns will begin to emerge that will help anticipate peak bloom timing. For example, it might become clear that when trees reach 50 percent of a certain stage, peak bloom will follow in a month or less, he explained.

Kim, a UW associate professor of environmental and forest sciences, said he is eager to see the early results of the bloom timing data. The model he developed to help predict the D.C. peak bloom period needs rigorous testing before it can be applied for the trees on the UW campus, mainly because of the differences in regional weather patterns as well as tree genetic backgrounds.

The cherry bloom data collected at UW could prompt additional research and help improve the ability to provide more accurate bloom predictions through advanced observations as well as models, Kim added.

The iconic cherry trees in the 天美影视传媒’s Quad reached peak bloom March 29, and this weekend will be prime viewing to see the blossoms. Peak bloom is when at least 70 percent of the blossoms have emerged.

The amount of daylight and favorable temperatures are the two most important factors that determine bloom timing, said Sara Shores, UW arborist. If it stays cool, with little rain or wind, the blossoms could stay on the trees for as long as two or three weeks.
Peak bloom is about a week or two later than usual, probably because of the record-breaking snowstorm and cooler temperatures this winter, Shores said.

The 29 large cherry trees in the Quad are about 86 years old and healthy. A number of other cherry trees live across campus, but the species in the Quad, “Somei-yoshino,” usually blooms before the others each season. Each species has its own typical bloom time.

Read more:

Contact: Kiyomi Taguchi, UW News video producer: ktaguchi@uw.edu or 206-685-2716