On a late-September afternoon, the Research Park Greenhouse at 1380 30th Street will open its doors to anyone curious enough to walk in. The occasion is Cyanotyping at the EBIO Greenhouse Collection, a free open house running from 1 to 3 p.m. on Wednesday, September 30, 2026, part of CU Boulder's campus-wide Culture Crawl. Visitors will press leaves and petals onto light-sensitive paper and let the Colorado sun do the rest, turning plant matter into deep Prussian-blue silhouettes. They'll wander a teaching collection of more than a thousand species with a scavenger-hunt sheet in hand, and they'll meet the people behind the campus apple orchard and a project documenting Colorado native plants in the Arapaho language.
It's a rare invitation. The 30th Street facility is the largest of the university's greenhouses, with 8,753 square feet of growing space under glass, compartmentalized into rooms kept at different temperatures and humidity levels. It houses the majority of the EBIO Plant Teaching Collection and is, on ordinary days, a working research facility rather than a public attraction. The department maintains several greenhouses in all: two ground-level houses near Macky Auditorium, a single-room facility on the roof of Ramaley Hall, and the big compartmentalized building on East Campus. Volunteers tend the 30th Street collection every Wednesday. The open house is one of the few times a year the public is invited to simply look.
The cyanotype activity is a nod to one of the strangest and loveliest accidents in the history of science. The process was invented in 1842 by Sir John Herschel, the English polymath — mathematician, astronomer, chemist, and experimental photographer — who was looking for a way to copy his own notes. He found that paper coated with iron salts, exposed to sunlight and then washed in water, produced a permanent blue image. The technique became the blueprint process, and for decades it was how engineers duplicated their drawings. But it was a botanist who turned it into art. Anna Atkins, a British plant collector who supplied specimens to botanists at Kew Gardens, used Herschel's method to publish Photographs of British Algae: Cyanotype Impressions beginning in 1843 — widely regarded as the first book illustrated with photographs. Atkins laid actual algae specimens on the paper and let the sun record their outlines, producing images that were both scientific documentation and, inadvertently, some of the earliest photographic art. The prints visitors make at the greenhouse will be direct descendants of hers: plants pressed to paper, exposed to light, rinsed, and hung to dry.
The scavenger hunt sends visitors through a collection that is, in the greenhouse's own description, not easily replaced. The EBIO Plant Teaching Collection holds over 1,000 species across roughly 150 plant families, assembled from collectors in the United States and abroad, from specialty growers who may no longer be in business, and from sources that were only available at an earlier moment in time. Increasingly, it includes rare and endangered plants. Most plant science courses in the department rely on it. Among the collection's newer residents is a Wollemi pine — a species known only from fossils until 1994, when an Australian park ranger found a small stand hidden in a remote canyon. Fewer than 100 remain in the wild. The tree at CU Boulder, nicknamed "Wally," arrived after alumni Judy and Rod McKeever, who had raised it as a sapling for nearly two decades, found it had outgrown their Boulder home and asked the greenhouse to take it in. "The Wollemi pine is an interesting story about paleobotany as well as conservation," greenhouse manager Malinda Berberio said when the tree arrived. "Where we are right now with climate change, we are losing plant and animal species. As scientists and horticulturists, it is our job to maintain the diversity of the world in collections, and Wally is an important part of that."
The Boulder Apple Tree Project, meanwhile, brings a story that starts with a child's question. In 2017, CU Boulder ecology professor Katie Suding's children spotted an old apple tree growing improbably on open prairie near their home. Suding pulled together scientists, historians, and community members to ask how it got there. The answer turned out to be a lost industry. In the late 1800s, much of Boulder's land was planted for fruit, and near the turn of the century Colorado was one of the top apple-growing states in the country. Orchards supplied the hotels near Eldorado Canyon and lined the ditches of North Boulder; aerial photographs from the 1930s still show where they stood. Then disease, drought, and Prohibition combined to gut the industry, and the rise of the Red Delicious cemented Washington State's Columbia Valley as the nation's apple capital. Boulder's orchards fell into disrepair.
Many trees survived anyway, on small farms and in family recipes, and they carry genetic diversity that commercial production has since shed. The project launched its first "Apple Blitz" in 2018, documenting trees across Boulder County, and found more than 1,000 heirloom apple trees still standing — while losing roughly 10 percent of them each year to old age. Because apples don't grow true from seed, the only way to preserve a variety is to graft a cutting onto new rootstock. The project has begun planting new orchards to hold those genetics, including one planted in May 2025 near the CU Boulder greenhouse, just off 30th Street — a short walk from where the open house will be held.
The Arapaho plant names add another layer. The Arapaho Language Project at CU Boulder documents roughly 100 plants known and used by the Arapaho people, sorted into four categories: food, medicine, ceremony, and plants used for tools, implements, and dyes. Many plants had several uses at once, and a number of Arapaho plant names survive for which no corresponding species can now be identified — evidence, the project notes, of how much traditional knowledge has been lost. Visitors will be able to explore those names and their cultural significance alongside the living plants themselves.
The Environmental Center, which co-hosts the event, has been part of campus life since 1970, when students founded the Eco-Center. Three years later, students voted to fund it through their own fees, and in 1976 the same mechanism launched CU Recycling. The center has since run the campus bus pass program, helped CU buy more recycled than virgin paper for the first time in 1994, and grown into what it describes as the hub for student-led sustainability. At the open house, its staff will be on hand with information about programs and resources.
The event is free and drop-in, and it's one stop on the Culture Crawl, a campus-wide celebration of CU Boulder arts and culture that runs alongside Homecoming. Visitors can pick up a free Culture Crawl t-shirt at any event while supplies last, and students can swipe in with a Buff OneCard to enter a prize raffle; the more events attended, the more chances to win. But the real draw at 30th Street is simpler: a working greenhouse that usually keeps its doors closed, a collection of plants gathered from around the world, and a sheet of blue paper that turns a leaf into a photograph.