Plant-Spotting

A Life of Science: A Series by New Scientists

All parts of the plant are toxic and, if taken in the right dosage, can have powerful hallucinogenic effects. If taken in the wrong dosage, you die.

I’m searching for these plants as part of my doctoral dissertation in Ecology and Evolutionary Biology at the University of Arizona. My dissertation involves studying how plants manage their resources and divvy them up between survival, growth, flower production, and seed production. Although I am focusing on resource investment at the level of an individual plant, how plants split up resources into flowers and fruits can have drastic effects on the species that interact with them. For example, if a changing nutrient environment causes plants to produce fewer flowers, there will be less food available to pollinators. This would then lead to pollinator populations decreasing and potentially going extinct. Plants can’t move, which makes them great for studying how resource availability affects them. They can’t get up and go somewhere else with more resources like animals can. You would think this would make them easier to find, collect, and grow in a greenhouse. It does not.

Previously, I’ve worked with another Arizona native, the chiltepin pepper, to determine how plants allocate their resources. The chiltepin (Capsicum annuum) is the wild mother of most of the peppers we eat today, from the mild bell pepper to the fiery jalapeño. Interestingly, this wild ancestor is several orders of magnitude more spicy than many of its descendants. My work with the chiltepin involved growing plants in the greenhouse in different resource environments and measuring the size of the plants, the size and number of flowers, and how spicy fruits are in order to determine how the plants invested their limited nutrient resources into growth, reproduction, and defense, respectively. Through the course of my time in Tucson, though, I’ve decided that it’s better to study a much wilder group of plants.

Enter Datura, a genus of 18 species of plant in the tomato family, Solanaceae, spread out across the American Southwest and Mexico, that I’ve been studying and hunting for the last three years. People in the Southwest may know Datura plants by a couple other names: moonflower, moon vine, and—my favorite—devil’s trumpet. Each species has large, white flowers that open at dusk, hence the moon, and point directly up, which if you look at them the right way may look like trumpets bellowing from hell (funnily enough, the sister genus to Datura, Brugmansia, has large, flared tube-shaped flowers that point down, and are thus known as angel’s trumpets).

Each species’ flower has a signature scent, from the spicy notes of Datura stramonium to the sweet Datura wrightii¸ whose flowers smell like Starburst candy. My personal favorite are the flowers of Datura discolor, which have a subtle and mature almond scent, like a librarian’s perfume. All parts of the plant (even the small seeds and probably the nectar too) are toxic and, if taken in the right dosage, can have powerful hallucinogenic effects. If taken in the wrong dosage, you die.

I don’t usually think about this as I’m planting the seeds, counting leaves, and harvesting their spiny fruits. I do make sure I always wash my hands after I handle them, though. The compounds are powerful deliriants and, allegedly (I’ve never tried it, I don’t have a death wish), cause memory loss, make people violent, and cause people to think they can fly. The only hint of this property is the rank stench of rotten peanut butter that emanates from the foliage. Handily, this is another good clue in the field that you’re near a patch of Datura.

I’ve been to plenty of interesting places looking for these plants. I’ve been under highway overpasses that are home to colonies of free-tailed bats, hiked through small natural areas in the middle of retirement communities, and trekked through the dry riverbeds and washes that crisscross Tucson and the surrounding desert landscape. My favorite spot was under the overpass that crosses Greasewood Wash, in Tucson, where I found strange occult and alchemical signs spray-painted on the walls.

Sometimes I feel like I can’t escape them. I found a big Datura wrightii outside of my apartment the other day. It’s pretty big, but the leaves are starting to droop from lack of rain. I now feel obligated to water it.

Even though my lab has been studying Datura for over 20 years, they’ve primarily worked with Datura wrightii, which is found in pretty much every ditch in Arizona. I’m trying to find the other three to five species that grow here so I can compare how different species allocate their resources. Increasing the number of species will allow me to make broader statements about how plants, as a whole, spend their finite resources and how their strategies may be affected by whether they are perennials or annuals.

My white whale, Datura quercifolia—a  species with beautiful oak leaf-shaped leaves—has led me down dusty roads and across dry riverbeds. The only guides I have are personal accounts from 1996 (the year I was born) and a general idea of what habitat it would usually grow in. The plants are supposedly in a remote area near Sonoita, Arizona, in a narrow valley hemmed by dry billowing hills and hauntingly pale sycamore groves. Given its remote location and obscure nature, no one has seen or reported its presence in the past 20 years.

From year to year a population of plants doesn’t tend to move much. Maybe they will move a couple feet as old ones die and new ones sprout, but over the course of nearly 25 years their location can change considerably.

A lot of these species are dependent on the arrival of the summer monsoon to germinate. Even though our summer monsoon on average is consistent, recent years have had pretty poor precipitation. As I have wandered through dry grass and scrubby oak the past couple summers, I have thought about how I could be walking over the plants right then, as they sit below the surface of the soil as seeds, just waiting for a couple days of consistent rain. Similarly, as I search for these plants my dissertation has felt as if it has been in a state of dormancy. Once I find them, just like the seeds hidden below the surface, my dissertation can sprout and bloom.

I don’t know how other people usually feel about their study systems, but I’ve grown incredibly fond of mine. I’m sure it’s easier to fall in love with something covered in fur, with legs and eyes, but I’ve found myself smitten with these plants. Every time I get my hands dirty mixing soil and planting seeds, I immediately feel more grounded. Graduate school can feel insubstantial because we’re always writing and working on projects that rarely have a tangible result. Living in Southern Arizona, where every day is sunny and warm and the seasons change subtly, also makes me feel out of sync with the natural world. Watching these plants sprout, grow, flower, and fruit brings me back into the flow of nature. Even though the Datura are incredibly dangerous, I always find my peace with them. Even when I’m dehydrated from hiking for hours searching, I know I will always smile when I find one of these straggly weeds hanging on.

Alex Karnish is a Ph.D. candidate in Ecology and Evolutionary Biology at the University of Arizona. He studies how plants split up their limited resources into flowers and fruits, and how that affects their animal pollinators and seed dispersers. Originally from the Midwest, Alex has been charmed by the desert landscape and his new plant neighbors.

Header photo of Datura by dae jeung kim, courtesy Pixabay.