Inhale the fragrance of coconut geraniums or spicy shell ginger, pop a citrusy kumquat into your mouth, and pretend you’re in the Mediterranean while the snowstorm rages outside. Welcome to the UWM Greenhouse, located on the UW-Milwaukee campus in Wisconsin.
I began volunteering at the Greenhouse after becoming a UWM employee in 2018. Before the COVID-19 pandemic, I would visit weekly to help with potting, dividing, propagating, pruning, grooming, and other tasks as needed. Since the pandemic, I have concentrated my efforts on managing the UWM Greenhouse Instagram account as a way to share the bounty with a wider audience while expanding my own knowledge of botany.
The UWM Greenhouse showcases biodiverse species representing the full evolutionary spectrum, from primitive mosses and liverworts to cycads to flowering plants. Rooms with different habitats, including desert and tropical, house nearly 700 plant species of over 110 plant families, including several that are rare or endangered in the wild. The collection has been maintained for more than 50 years and includes plants obtained from the wild, trades with other universities or conservatories, and seeds. The Greenhouse also includes labs that support student and faculty research.
With a wide variety of plants representing diverse ends of the plant spectrum, the Greenhouse is a great place to learn about botany. I’ve also benefited from invaluable hands-on experience and the wisdom of the Greenhouse Manager, Paul Engevold. In what follows I will share some of my favorite aspects of the Greenhouse: its rare and endangered plants, variety of primitive plants, the desert room full of cacti and succulents, and the rooftop native plant area.
Rare and Endangered Plants
The UWM Greenhouse is home to several rare, endangered, or unusual plants. In that sense, it serves as a repository for species that may be hard to find in the wild or even endangered or nonexistent in wild habitats, often due to habitat loss due to encroaching human activities.
Cabbage on a Stick
Cabbage-on-a-stick (Brighamia insignis) is a critically endangered species from Hawai’i that grew on clifftop habitats on the islands of Kauaʻi and Niʻihau. With fewer than 500 known individuals in the world, cabbage-on-a-stick is maintained in greenhouses such as the UWM Greenhouse in the hopes that it can someday be reintroduced into its native habitat. Learn more about the Greenhouse’s partner in this project at the Chicago Botanic Gardens
The evening of Saturday, April 17, 2021, was a momentous occasion: A corpse flower (Titan Arum) bloomed in the UWM Greenhouse. This endangered species has one of the largest flowers in the world and can take up to 10 years to bloom from the time it sprouts. Blooming is considered a very rare event in cultivation and even more rare in the wild. The plant is native to Indonesian rainforests but is uncommon in the wild as its native habitat is being increasingly destroyed. Only about 120 blooms have ever been witnessed in greenhouses worldwide.
It is the smell of decaying animal flesh that gives the plant its namesake. As evening approaches, the female flowers open and the bloom heats up, trying to entice pollinators such as carrion beetles, flies, and other active night-time insects.
Quite possibly one of the coolest plants in the Greenhouse is Welwitschia mirabilis. What’s so special about this plant? It’s commonly referred to as a “living fossil” because its closest plant relatives died out long ago (see cycads, below). Endemic to the Namib desert, it consists of only two leaves throughout its entire life, which can be as long as 1,000 years or more. They are specially adapted to survive the extremely arid environment in which they live, such as being able to harvest moisture from fog and perform a unique form of photosynthesis (CAM) that occurs without opening its leaf pores, allowing it to save moisture during the hot daytime hours.
I would be remiss if I didn’t mention the Greenhouse’s collection of carnivorous plants such as the Venus flytrap, sundew, and pitcher plants.
The pitcher plant is, without a doubt, one of my favorites. They have modified their leaves in the shape of pitchers, which collect water and trap insect prey.
When a crawling insect brushes against one of the hairs of the Venus flytrap, the trap prepares to close. It snaps shut only if it senses additional contact less than a minute later. This way, the plant ensures that it has caught a live bug and conserves energy by not snapping shut to trap something else that it doesn’t need (like a falling leaf).
The sundew (Drosera spp.) uses its sticky tentacles to catch insects for dinner. These also grow wild in some of Wisconsin’s bog habitats, such as the one shown here in Cedarburg Bog.
There are presently about 300,000 species of flowering plants in the world, representing 90% of all plant species. Flowering plants include most of those tasty fruits, vegetables, and starches that are the staples of our diet.
There was a time, however, when non-flowering plants like ferns and conifers ruled the planet. Plants such as mosses, clubmosses, liverworts, ferns, and cycads are all early forms of plants that dominated before the flowering plants took over. The UWM Greenhouse has many examples of some of these early plants.
Non-Vascular Plants: Liverworts, Mosses, and Hornworts
First came the bryophytes, which evolved from aquatic and terrestrial algae. These early plants are nonvascular, meaning, in simple terms, they have no stems. Thus, they grow low to the ground to be close to the water and nutrients they need. Think mosses as well as their lesser known cousins, liverworts and hornworts.
Early Vascular Plants: Ferns and Friends
Ferns and their cousins represented a major step up in plant evolution in that they were vascular plants: they had a plant body. The UWM Greenhouse has plenty of them.
The common Boston fern (Nephrolepis exaltata) is familiar to many. Of the common cultivated ferns, it is the most drought tolerant which makes it a very popular houseplant. The 1989 NASA Clean Air Study found that Boston ferns could filter dangerous chemicals from the air.
Other plants like spikemosses and clubmosses are more closely related to ferns, despite their name.
Early Conifers: Cycads
The UWM Greenhouse also houses several cycads. What are cycads? Think dinosaurs and the Jurassic period, which was dominated by these plants as well as ferns. Though they are less showy than other plants, they are models of longevity and hardiness, surviving more than 300 million years in small, scattered populations today. They now represent less than 0.1% of the world’s plant species, and many are protected due to rapid decline from human encroachment.
Unlike most other plants, cycads are dioecious, meaning that they produce male and female reproductive parts on separate plants (in this case, cones). Cycads are one of four still-existing types of gymnosperms which also include the Welwitschia plants mentioned above, conifers (like spruce and pine), and ginkgo trees.
The Desert Room
My favorite Greenhouse room is the desert room, where prickly, otherworldly creatures await. On one side of the room are “Old” World plants and on the other, “New” World plants. In this way, interesting patterns can be observed.
First, though, what’s the difference between a succulent and a cactus? They are closely related. All cacti are succulents, but not all succulents are cacti. “Cactus” denotes a botanical family, the Cactaceae. Most of these plants originated in the New World. Succulents are a larger group of plants that include any that have developed plant parts to store water, including cacti. Thus, the “succulent” label is more loosely defined. Many plants, regardless of origin, have developed succulent leaves or other plant parts in response to water scarcity, whether they are of New or Old World origin.
Old World Succulents
Many “Old” World species hail from Africa—southern Africa, specifically, which is one of the most biodiverse regions on the planet. Familiar succulents that originate from the south African region include jade plants, living stones, and haworthias.
Baby’s toes or window plant (Fenestraria rhopalophylla) is native to Namibia. Each leaf has a transparent window which allows light into the leaves for photosynthesis. The plant commonly grows under sand in the wild, with only its transparent tips protruding. The plant produces optical fibers that transmit light from the “windows” to underground photosynthetic sites.
Living stones (Lithops) also originate from South Africa where they have adapted unique methods for growing in harsh environments, such as growing fleshy “leaves” to retain moisture. Their stone-like appearance also helps them blend in to avoid being eaten.
The succulent Socotrian fig tree (Dorstenia gigas) grows on the Socotra Islands off the Horn of Africa. It grows a caudex—the fat, swollen trunk seen here. The flower head is a funny thing. It’s what’s called a pseudanthium or a “false flower”: Although the entire structure resembles a flower, the actual flowers are the numerous, tiny clusters on the disc-shaped center. Sunflowers and daisies are common examples of this plant phenomenon.
New World Succulents
New World succulents are primarily the cacti (Cactaceae) species of North and South America: all those spiney, pokey friends we love. The spines are actually leaves—modified leaves! Over time the leaves adapted into spines to fend off predators in the desperate environments they grow in, where food and water resources are scarce.
Rooftop: Native Plants
An outdoor rooftop terrace is home to several native Wisconsin plants. They are grown on the roof to simulate their natural weather conditions (including dormancy) and give them access to local pollinators. They remain in pots so that they can easily be moved inside to be brought out of dormancy and used for classes.
American witch hazel (Hamamelis virginiana L.) blooms in early November and is pollinated by bees, flies, and even moths. However, fertilization is delayed until May the following year. The fruits, which are contained in woody capsules, spend the entire growing season maturing until they explode in the fall and expel shiny black seeds several meters away!
Want to Know More?
For more information about the UWM Greenhouse, visit https://uwm.edu/biology/research/facilities/greenhouse/
Unfortunately, the Greenhouse is not open to the public except on rare occasions.
To learn the latest news, follow the UWM Greenhouse Instagram account.