Inside the Subtropical Dome at the Dennis K. Walker Greenhouse at Humboldt State University. | Photo by Deija Zavala

Green Thumbs at the Greenhouse

Dennis K. Walker Greenhouse provides a haven for a diversity of plant species.
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Dennis K. Walker Greenhouse provides a haven for a diversity of plant species

A sky full of grey clouds smothers the sun and with a chilling breeze even the most layered person shivers down to their toes. One step into the Dennis K. Walker Greenhouse transports you away from the cold into a world of warm, enticing, vivacious plants.

There are six rooms in the greenhouse: temperate, tropical, desert, fern, aquatic and the subtropical dome. Each room has an appropriate climate and a resident community of plants. Greenhouse manager Brianne Lee, along with student assistants Dabid Garcia and Courtney Harris, maintain the greenhouse at Humboldt State.

“Essentially, the greenhouse is a living museum,” Harris said. “It’s something that we are trying to preserve here and not kill with love.”

The large botanical collection contains more than 1,000 species of plants belonging to 187 families. According to the Department of Biological Sciences website, students and faculty studying botany and biology use the greenhouse and its plant life to research and learn.

Harris, a botany major, said the greenhouse is a magical place, especially since there are only two student positions. After transfering from the College of the Redwoods in 2017 Harris was hired as an assistant.

“It feels like a unique experience being that this is such a cool staple and an important part of the botany program,” Harris said.

The job of a greenhouse assistant consists of maintaining the facility and its residents residents, which means sweeping the rooms, hand watering plants, managing pests and propagating plants.

“Essentially, the greenhouse is a living museum. It’s something that we are trying to preserve here and not kill with love.”

Courtney Harris

Garcia, a rangeland resource science major, said that there’s a lot of care and research that goes into the plants, but the goal is to make sure the plants are happy and thriving.

“Every species needs their own little formula of fertilizer,” Garcia said. “Some require more nitrogen than phosphorus and some others more potassium. We have to do our own research and sometimes that research isn’t available, so we’ll give the plant fertilizer and see how the plant reacts to it. A lot of our plants are really rare in the wild.”

The trio look out for signs indicating whether something might be wrong, such as droopy leaves and discoloration. The team also checks soil moisture levels, but all plants indicate issues to caretakers in unique ways.

“The biggest challenge is understanding how each plant reacts and responds to the care that we give it, and adjusting our behavior accordingly,” Harris said. “It requires a tremendous amount of teamwork and communication between us.”

Harris added that some plants don’t like attention while others, if left alone, will wilt and die.

Mihai Tomescu teaches plant morphology, plant anatomy, paleobotany and general botany. The trio’s work supports Tomescu in the botany department, as well as supporting the biological sciences. Faculty often use plant specimens during lectures and labs.

“Plants don’t move, and yet they are exposed to pretty much the same challenges that we are exposed to in terms of surviving. There’s all sorts of stressors. They have to procure their food and because of that, just like other types of organisms, have to have some type of behavior.”

Mihai Tomescu

Tomescu said his area of expertise and research is plant structure, including topics like how plants are put together, how they grow, how they look and how their features evolve over generations. Some of his methods include digging deep into geologic time.

“I know how they grow at the cellular level,” Tomescu said. “So coming from that perspective, I realized that one of the most fascinating things about plants that people don’t realize is that compared to us animals, and compared to what we think of in our culture about aliens, is that plants are more alien to us than the craziest aliens that human imagination has come up with.”

In his classes, Tomescu has his students visit the greenhouse three to four times a semester for assignments and brings live samples for labs when examining roots, leaves, stems, cells and other internal parts of plants.

“If you have a big botany program that emphasizes organismal biology, the diversity of plant groups and so on, then it makes sense to have something like this,” Tomescu said. “How else are you to teach your students about the diversity of plants if you can’t show it to them alive.”

Some people may question the general interest in plants because at the surface they seem not to do anything. But Tomescu said that if you are able to slow down and get pass the green blur of a forest of plants, you’ll come to find some interesting organisms.

“Plants don’t move, and yet they are exposed to pretty much the same challenges that we are exposed to in terms of surviving,” Tomescu said. “There’s all sorts of stressors. They have to procure their food and because of that, just like other types of organisms, have to have some type of behavior.”

Plant behavior is what a plant does, including how it grows. According to Tomescu, plants have control of their growth, from the depth of their roots to the direction of their leaves.

“The plant makes a lot of choices because growing in one direction or another means spending energy,” Tomescu said. “It’s very calculated — not consciously calculated– but basically plants sense their environment very well.”

In the broader sense, he said that plants make him think. Tomescu hopes more people will become interested in plants since they are so different compared to other life forms.

“It’s kind of exhilarating to realize that we live next to these super weird organisms,” Tomescu said. “It maintains this fascination that there are these organisms that do the business of living in a very different way from us.”


The Dennis K. Walker Greenhouse is available to instructors and students in the Department of Biological Sciences, and access is limited by the availability of instructors or greenhouse staff.

It is open to the public by appointment or when greenhouse staff are available. If you are interested in making an appointment contact Brianne Lee at 707-826-3678 or schedule a visit via email at bms561@humboldt.edu.

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