With its heart-shaped leaves, the climbing Aristolochia may appear innocent enough, yet its malodorous flower smells like decayed carrion to attract flies and beetles. The Vachellia cornigera, meanwhile, provides food and lodging for ants that can surge and bite any insect or animal predator that touches the plant. The 25-foot traveler’s palm houses a less confrontational tenant in one of its hollowed-out leaf sheaths: a tiny Pacific chorus frog that popped its head out during a recent visit.
These are just a few of the 250 tropical plants on display in the newly rebuilt Virginia Haldan Tropical House at UC Berkeley’s Botanical Garden, the East Bay’s only tropical greenhouse open to the public. After being closed for four years, Tropical House will reopen its steamy doors on Saturday.
To celebrate, the house will be staffed with docents Saturday and Sunday from 10 a.m. to 4 p.m. to answer questions about the collection, which includes rare tropical cycad species from the garden’s research greenhouses that are on view to the public for the first time.
The 40-foot tall, 40-by-40-foot facility boasts a re-envisioned interior designed by the renowned San Francisco landscape architect Ron Lutsko that includes a larger pond, a double-sided living wall by the Berkeley-based Habitat Horticulture, and an ADA-compliant design that allows about 30 people to closely interact with flora. On average, the garden hosts 100,000 visitors per year, including K-12 students from the Bay Area and elsewhere.
Lutsko, a garden adviser board member, offered his firm’s services pro bono. He is also a UC Berkeley alumnus who received a master’s degree in landscape architecture in 1990. His work reflects his interest in ecological systems and incorporates sustainability into his often naturalistic large-scale landscape designs.
The entire $2.3 million renovation was paid for by donations from garden supporters and donors, including members of the garden’s advisory board. Of that, interior improvements and the covered entrance plaza cost $1.3 million. “Significant support” for the building’s $1 million exterior renovation and climate control systems came from the family of the late Virginia Haldan of Mill Valley, according to a statement prepared by the Botanical Garden, which led to the renaming in her honor.
Back in the ground
All of the plants in the collection are labeled, and about 10% of them contain a red dot, which means they are rare and/or endangered in the wild. The oldest member in the collection is a natal grass cycad (Stangeria eriopus) that dates to 1958. One of the collection’s most unusual plants is the Selaginella willdenowii, which is iridescent and reflects light.
The collection also boasts a large number of rare cycads, gymnosperms that superficially resemble palms but are not actually palms, some of which are the most endangered plant groups on earth and extinct in the wild.
“They are very slow growing and are dioecious,” said Andrew Doran, the museum’s director of collections, meaning they have separate male and female plants, which makes pollination more difficult. Standouts are species like Microcycas calocoma from Cuba and the Cycas bifida from China and Vietnam. About five new cycad species, like Bowenia serrulata from Australia, are among the newcomers.
For the living wall, Habitat Horticulture supplied most of the plants since the garden does not have enough duplicates of individual species to cover two sides of the 7-by-11foot wall. Some of the species in the display are recognizable houseplants like the reverse spider plant and maidenhair ferns. Since day one, Corina Rieder, the glasshouse horticulturist, has been swapping in plants from the garden’s collection, including the rare green-flowered orchid called coelogyne and huperzia, an ancient lineage of early plants that have a spikey, Dr. Seuss-like look.
Though most of the plants have only been in the ground for the past three or four weeks, they are showing signs that they are happy. The Euryale ferox, a Southeast Asian water lily whose leaves can grow up to 3 feet in diameter, sends up an underwater leaf. The Macleania pentaptera, a.k.a. tropical blueberry, produces orange and green flowers and translucent white fruits. There are others, too, whose blossoming is cause for celebration.
Originally from Ecuador, the Macleania pentaptera is in the same family as blueberries and cranberries and produces a white, translucent berry-like fruit. Credit: Ximena Natera, Berkeleyside/CatchLight
“Oh my gosh, the tropical rhododendron is in flower,” Doran gushed, as he stepped into the garden for a closer look. “You don’t think of a rhododendron as being tropical.” Nor do you think of a rhododendron as having orange flowers like this one, Rhododendron macgregoriae, from Indonesia.
When the building was emptied to make way for the renovation, most of the plants were potted and brought to the garden’s Jane Gray greenhouses. Rieder was in charge of the move and maintains the Tropical House collection.
“Basically, it’s this sigh of relief for everything now that they’re back in the open ground and allowed to really root down again,” Doran said. “Every day, Corina and I are noticing little changes. It’s exciting to see all this new growth. In another year, the change will be remarkable.”
The old Tropical House ‘aged out’
With its lush, exotic flora and steamy environment, Tropical House has long been a favorite stop for garden visitors since it opened in 1974. Its educational focus was on plants of economic interest and used by humans for food, medicine or other uses, a mission that continues today.
Throughout its history, the building “was a challenge to maintain as heating and irrigation systems regularly failed,” according to the garden’s statement. The original pond was a prefab, molded variety intended for suburban backyards and was so bare bones it didn’t even have filtration or heating. In 2018, when some of the building’s glass panes cracked, engineers recommended a renovation and seismic retrofit.
The building closed to the public in 2020 to undertake that work. While most of the plants went into the greenhouses, the 25-foot traveler’s palm, 15-foot silver palm and several cycads proved too tall to be removed, so barricades were built to protect them from the construction.
“It was aging out,” Doran said of the previous structure. What did not age out, though, was the aluminum frame that “looks like it was constructed yesterday,” he added. “So the building basically got reskinned.”
Unlike glass, the polycarbonate exterior provides insulation for better temperature control and prevents direct sunlight from scorching tender tropical leaves. The building was also rewired and replumbed, which allows it to maintain a temperature of 70 to 85 degrees with at least 70% humidity. The new pond, with a state-of-the-art filter, UV filter, pump and heater, keeps the recirculated water at a spa-like 80 degrees.
Once exterior renovations were completed in 2021, the garden staff recognized an opportunity to revamp the building’s interior. Another round of fundraising ensued.
In its design statement for the project, Lutsko Associates wanted to highlight “the growing significance of the tropical rainforest ecosystem in our climate-changed world” by making water the central feature of the space. The green wall at one end of the water feature also encourages “an immersive experience and emphasizes the connection of plants and water in sustaining a healthy rainforest environment.”
Both features are connected, with the living wall acting as a backdrop to the pond. The wall also provides an outlet for the floating spillway that creates a thin, horizontal waterfall, adding the sound of trickling water to the tropical atmosphere.
The redesign also brings visitors closer to the plants with a more circular route through the collection that provides a more unobstructed view of the plants at eye level.
“The other house had very deep borders so you really couldn’t see a lot of what was going on,” Doran said. “Because you now have all these fingers of the path intruding into the collections, you can get up close and personal with the plants. Once everything gets filled in, you won’t be able to see people on the different pathways.”
Added to the plans was a covered entrance plaza that will provide a gathering point where docents and teachers can orient visitors before entering and doubles as a covered reception area for parties. Seating includes two redwood benches Lutsko had milled from a 179-foot felled redwood that came down duringin the so-called “bomb cyclone” of March 2023. The third bench is within the house, to take in the pond and living wall.
For the public — and researchers, too
In addition to its educational mission for the public, Tropical House continues to be available for study. For example, right now, a UC student is working with the university’s Center for the Science of Psychedelics to prove that the blue lotus sold today as a psychoactive drug is not the same species in the pond.
“What they’re buying is not blue lotus,” Doran said. “A lot of these claims are false advertising.”
Tropical House also provides specimens for Cal’s University and Jepson Herbaria, where Doran had worked for almost 12 years. Graduate students and volunteers are constantly making herbarium specimens for research, a process that involves pressing all of a plant’s parts onto an 11×17 sheet of paper. Such efforts will ensure that when plants die, a research record and so-called “DNA voucher” will be available for future study.
“Since plants have a limited life span, from annuals to long-lived perennials, we preserve them indefinitely for future generations,” Doran said. “It’s basically a Noah’s Ark in here.”
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