[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 ����Ӱ�Ӵ�ý 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.

Plants can fight back, unleashing an array of chemical defenses to discourage wayward foragers — from releasing chemicals that to secreting compounds that make the plant that desperate caterpillars resort to cannibalism. But scientists know little about how plants detect these attacks and marshal defenses.

In a published Nov. 23 in the Proceedings of the National Academy of Sciences, a team led by scientists at the ����Ӱ�Ӵ�ý and the University of California, San Diego reports that cowpeas — a type of bean plant — harbor receptors on the surface of their cells that can detect a compound in caterpillar saliva and initiate anti-herbivore defenses.

“Despite chemical controls, crop yield losses to pests and disease generally range from 20-30% worldwide. Yet many varieties are naturally resistant or immune to specific pests,” said lead author , a UW assistant professor of biology. “Our findings are the first to identify an immune recognition mechanism that sounds the alarm against chewing insects.”

The receptor is a protein known by the acronym INR. The team showed that, in response to both leaf wounds and the presence of a protein fragment specific to caterpillar saliva, the cowpea’s INR protein boosts the production of ethylene, a hormone that plants often produce in response to munching by herbivores and other types of environmental stress. The protein fragment in caterpillar spit that elicited this response, Vu-IN, is actually a fragment of a cowpea protein, which gets broken down by the caterpillar as it dines on cowpea leaves.

Researchers have fewer methods to study cowpeas compared to other plants. So to learn more cellular details about INR’s function, they popped the gene for INR into tobacco plants. These tobacco plants, when exposed to Vu-IN, increased production of ethylene as well as reactive oxygen species, another anti-herbivore defense that consists of chemically reactive forms of oxygen. In addition, the team’s experiments showed that a tobacco-eating caterpillar — the beet armyworm — munched less on INR-harboring tobacco plants than plants without INR.

The research shows that plants like the cowpea sound the alarm only after their cells detect specific molecules associated with herbivory. Vu-IN is a trigger for cowpea defenses. Other plants likely have different molecular triggers for their own defensive systems, the researchers believe.

Understanding how plants activate their immune systems could help scientists develop more effective strategies to defend crop plants against hungry insects.

Co-authors are UW research scientist Antonio Chaparro; of Colorado State University; Jessica Montserrat Aguilar-Venegas of the National Autonomous University of Mexico; Sassoum Lo and of the University of California, Riverside; Satohiro Okuda of the University of Geneva in Switzerland; Gaetan Glauser, Julien Dongiovanni and of the University of Neuchâtel in Switzerland; Da Shi, Marlo Hall, Daniel Crubaugh, Ruben Abagyan, and at UC San Diego; and Nicholas Holton and Cyril Zipfel of the University of East Anglia in the U.K. The research was funded by UC San Diego, the Life Sciences Research Fund, the University of California system, the Washington Research Foundation, the U.S. Agency for International Development, the European Research Council, the Gatsby Charitable Foundation and the U.K. Biotechnology and Biological Research Council.

For more information, contact Steinbrenner at astein10@uw.edu.