by August Linton
Originally printed April 12, 2023
Nestled between the science buildings, fronds sway in the breeze, fallen needles line the edges of paths, and cones of all shapes and sizes swell and release pollen or seeds. A deft hand plucks berries from one, and rolls between callused fingers the foot-long leaves of another. Professor emeritus of Botany Dennis Walker strolls slowly from plant to plant, and knows them all by common and scientific name, without a glance to the placards which define them.
The Cal Poly Humboldt campus hosts an extensive collection of conifer species in the Science Complex Conifer Collection, ranging from local Coast Redwoods (Sequoia sempervirens) to the Japanese Umbrella Pine (Sciadopitys verticillata.) Over 65 species of conifers grow close to the classrooms where they are studied, a collection that rivals the top universities in the United States.
Professor Emeritus of botany Dennis Walker made it his mission to expand the university’s collection, traveling to Australia, China, Chile, and many other places around the globe to bring back trees to use for teaching and research.
“In the beginning, I could simply go down to the local retail nursery,” said Walker.
After he had exhausted the list of plants available locally, Walker turned to botanical collections, cultivating relationships with other botanists and collections worldwide.
“It’s great to be a botanist in the jet age,” said Walker. “I was traveling with a backpack on my back, in my grubby clothes to slop around in some tree fern gully or something of the sort, complete with leeches.”
The collection is used by botany professors as a teaching resource, supplanting the need for jars of leaves, branches, and cones suspended in preservative.
Conifers are diverse in lifestyles, appearance and native habitat. Iconic examples of the group have dark green, skinny needles and small, pointed cones, but others have broad leaves, paired cones, or sweet, edible cones. The Plum Fir (Podocarpus elatus,) planted next to Science B, grows translucent-white, cherry-sized cones when in season.
Their diversity makes conifers a valuable resource for botanists who study paleobotany, the science of ancient plant form and evolution.
“Just collecting what is available [in Humboldt] is an easy way out, but students get a very narrow and inaccurate view of what the whole taxonomic order Coniferales represents,” Walker said. “They cannot conceive of something with a slightly widened leaf like that…you can tell them that there are such things, but it’s better to show them.”
The climate in Humboldt is uniquely suited to accommodate an extremely wide variety of plant species, one factor which made the collection possible, according to Walker. Some frost-tender plants are able to be planted outside, an important factor since the greenhouse severely limits their growth.
“There’s a banana belt that we’ve identified, where the cold air intake for the mechanical room keeps the air moving on the south side of [Science] A,” said Walker. “That was about the balmiest environment we could find.”
One species that Walker was unable to find for the collection was the parasitic conifer Parasitaxus usta, which grows on another conifer species. He traveled to New Caledonia to seek specimens of the plant, but was unable to find any. The host plants on campus weren’t strong enough to host the parasite either, according to Walker. International regulations on transporting plants across borders made it difficult to bring some specimens back into the country.
Arborists and student volunteers tasked with caring for the trees once Walker brought them back home have struggled to keep some species alive. Many individuals died from water mold, and some Southern Hemisphere species can only be kept in the greenhouse that bears Walker’s name.
Walker laughingly refers to botany professor Mihai Tomescu as his replacement. Tomescu describes the collection as a tool both for teaching and for research. A former masters student of his, Kelly Pfeiler, is now pursuing a PhD at the University of Kansas. She recently returned to the CPH campus to collect cones from specimens in the collection, to use as reference for paleobotanical research.
“She’s one of several people who have come through over the years from other campuses to collect here, because it’s a very diverse collection,” said Tomescu. “Dennis left a great legacy here.”
