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Sunday, October 24, 2021

A wildflower guide to the Arboretum

The flowers of UC Davis and their impact on the local organisms and communities

A great place to find wildflowers in Davis is the UC Davis Arboretum and Public Garden. The Arboretum is made up of 100 acres of land and includes demonstration gardens, scientific collections and the Putah Creek Riparian Reserve. Their mission is, “To inspire human potential to help people and environments thrive,” according to the Arboretum and Public Garden website.

Rachel Davis works at the Arboretum and Public Garden as a GATEways horticulturist. Davis has the responsibilities of being a mentor for the habitat horticulture team and managing some of the Arboretum’s collections such as the habitat gardens and environmental gateway, the foothill redbud desert contemplative garden and the terrace garden. She is aware of all the plants that are blooming this spring.

Some of the trees that are growing right now are the desert willows that are a part of the desert collection in the Arboretum. They are also located in the hummingbird garden by Scrubs Cafe on campus. These yellow flowered trees are drought tolerant since their natural habitat is the desert. Hummingbirds are one of the many local pollinators that visit these trees. They are a good size and fit for a home garden because they are more like large shrubs than huge trees, according to Davis.

Coral trees are also on display right now. They are from all over the world and are featured in the Argentine section of the Arboretum, as well as in the Storer Garden and the habitat gardens also near Scrubs Cafe.

The yellow trumpetbush is displayed throughout the Arboretum. The trumpet flowers are sources of food for hummingbirds and other pollinators.

Grevillea thelemanniana are year-round flowers that are also important sources of food for hummingbirds. They resemble clusters of red ribbon among the green space.

Another species Davis wanted to highlight is milkweed. Different species of milkweed are starting to bloom and they are host plants for the monarch butterfly as well as the honey bee. They are displayed in the Mary Wattis Brown Garden on campus.

“There is a little meadow out there and little stepping stones that you can walk through the meadow and really experience and take them in,” Davis said. “That is a highly recommended spot right now.”

These plants spread throughout gardens by rhizomes. 

“If you plant it in one area, it can move throughout your garden, so give it space,” Davis said. 

Kimberly Chacon, a Ph.D. candidate in the Geography Graduate Group at UC Davis, has done research on the most popular flowers for pollinators. Chacon did her dissertation research at the UC Davis Arboretum and Public Garden and monitored all the gardens for pollinators to see which pollinators were feeding on which plants and if there were indications of habitat fragmentation. 

Chacon is fascinated with the idea of designing connected habitats for bees. It has not been well understood until now, according to Chacon.

“It is a complicated topic that requires more studying,” Chacon said.

Chacon conducted a study that showed that, based on all the foraging events she saw in the Arboretum throughout a year, there were approximately 34 bee genera found and they were feeding on 303 different plant genera. 

“There’s different mixes of how they match up. You have the bee type and the flower type and sometimes they interact and sometimes they don’t,” Chacon said.

Of the 7,800 breeding associations she saw between all of the gardens, there were 589 bees paired with salvia.

Salvia is the most diverse plant genera in existence and this creates conditions for a lot of unique pairings between bees and the different types of salvia flowers. 

Another pollinator-friendly flower is the California Fuschia. Rachel Vannette, an assistant professor in the Department of Entomology and Nematology at UC Davis, is researching California fuschia flowers and the value of their nectar. For one of the classes Vannette teaches, she does a project where students sample nectar from fuschia flowers in the Arboretum and measure instances such as pollinator visitation and see how it corresponds to the amount of nectar that is bound in the flower.

“The Arboretum is really cool in that we have over 10 different cultivars or genotypes of California Fuschia that differ in when they flower, how big the flowers are, the color of the flowers and amount of nectar they produce,” Vannette said.

The California Fuschia grows throughout the Arboretum and starts flowering in late June and the beginning of January. They are abundant floral resources for many pollinators. These long red tubular flowers produce nectar that is 25% sugar by weight and are a great source of food for the Anna’s hummingbird, carpenter bees and honey bees, according to Vannette.

Carpenter bees have strong jaws and bite through the side of the flower tube because their tongues aren’t long enough to reach the nectar. They make it possible for other organisms with short tongues to obtain nectar as well. This is something to look for when walking in the Arboretum.

“[The walker] can look at the side of the flower and see if there is a hole there,” Vannette said. “If there is a hole, that probably means it has been chewed on by a carpenter bee. But if they are just walking past, I would appreciate the diversity of flower colors and morphology and really the diversity of the form the flowers take because each of the different varieties benefits different types of pollinators.”

Flowers are more than just pretty things to look at. They are also embedded into moments in our life. Anita Shahriary works for the Arboretum and Public Garden through the Learning by Leading Program and is a GATEways outreach internship co-coordinator. Flowers have defined key moments in her life, especially at UC Davis.

“Anytime I see lavender I think about the story where me and my roommate used to go to the lavender plants outside the lab science building, and we used to go pick those flowers and take them back to the dorm,” Shahriary said. “I feel like [the flowers] are a big part of my life and so I can find a way to connect it to every step of my way.”

Written by: Francheska Torres — science@theaggie.org

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