The Borneo camphor tree (Dryobalanops aromatica) exhibits a perfect example of crown shyness. Photo from Wikimedia commons at the Kuala Lumpur Research Forest
I spent a lot of time in my childhood lying in our backyard hammock, reading. Inevitably, I’d take a break and stare up at the tree canopy above me. We had sweetgum trees in that corner of our yard, and I’d watch squirrels chasing each other through the branches. One thing I noticed, but never really investigated, was how the highest branches spread out towards each other from the clump of trees, yet didn’t touch or overlap each other. You could nearly always see gaps of sunlight outlining the individual trees.
The canopy of mature oak trees exhibiting crown shyness. Photo credit: Carrie Stevenson, UF IFAS Extension
The term for this is “crown shyness.” As anthropomorphized as that seems, it’s an apt description for this seemingly polite growth pattern. The topmost branches of any given tree are in constant competition with each other for sunlight. Being photosynthesizers, sunlight is life. No growth can happen without the basic ingredients of sunlight, water, and carbon dioxide. So, from a tree’s perspective, there is an inherent disincentive to send growth beneath their own existing branches or those of an adjacent tree. The result of this is a botanical dance of sending branches out, neighboring trees doing the same, and multiple trees subtly angling for light. It’s like sharing an armrest on an airplane with a stranger. There’s a limited and highly desirable resource (the armrest), resulting in a (hopefully) gentle back and forth where someone either claims the space fully or you make an unspoken agreement to share it. If you do share it, it’s rare your arms touch; most of us want to keep some personal space!
Like Blue Angel jets in the diamond formation, trees will keep just a bit of sunlight between them and their neighbor. Photographed by Mass Communication Specialist 1st Class Ian Cotter. Official U.S. Navy Photograph.
While we may consciously shuffle for position in crowded public spaces, this happens for trees at a metabolic level. Evidence from an Argentinian study demonstrated that trees can “detect the presence of neighbors before being shaded by them,” using an internal sensor that detects light on the red:far red spectrum. This botanical spidey-sense comes from light-receptor proteins called phytochromes, which send out an alert that they’re close to another tree and may want to stop sending branches that direction. Growing into an adjacent tree quickly brings diminishing returns for absorbing sunlight, and it is in the tree’s best interest to keep a safe distance.
Single-species stands of pine trees exhibit crown shyness. Photo credit: Tyler Jones, UF IFAS
Crown shyness appears to be more pronounced in groves of same-species trees. Monocultures like pine plantations, or even large stands of black mangrove, exhibit the same growth patterns and timing, adapting to environmental factors the same way—particularly if they were planted or germinated at the same time. Foresters or ecologists trying to maximize the space for timber, fruit, or ecosystem restoration may want to deliberately encourage a diverse array of species, which fill in the gaps beneath the canopy and survive on less direct sunlight.
Maybe we could call it “crowd” shyness when people step back to give folks room to dance, avoiding “mechanical abrasion”! Photo credit: Cole Stevenson, University of the South
Another contributing factor to crown shyness, and perhaps one of the more crucial ones, is “mechanical abrasion.” University of Florida botanist Francis “Jack” Putz conducted research on this in Costa Rica back in the 80’s, which is still frequently cited in more recent publications. His team’s findings showed that crown shyness was “positively correlated with the distance pairs of trees adjacent to the gap swayed in the wind.” When tree branches physically bumped into one another on a regular basis, they kept their distance to prevent bud, bloom, and branch tip damage. For this scenario, imagine someone dancing enthusiastically in the middle of a big music festival—if there’s room, people will often spread out. The more the person flails, the more space you give them. If they’re just minimally swaying back and forth, you might stand closer. Putz, et. al observed this same principle in the coastal mangrove forests—more flexible branches adjacent to one another gave each other more space, while those with “stiff crowns” that couldn’t move much grew closer together.
When space opens up due to the loss of a neighboring tree or branch, the infusion of sunlight/fuel spurs a tree to send energy quickly to gain the advantage over adjacent trees. Tree species vary in their capability and success in doing this. An earlier article on pioneer species (the first to occupy a newly open space) and the process of succession sheds more light on this natural phenomenon. In a mature forest, the end result is a balanced mosaic of tree branches reaching out and nearly touching one another, but leaving each other space to grow.
A large Carolina wolfberry shrub thrives near St. Marks’ lighthouse at the wildlife refuge. Photo credit: Carrie Stevenson, UF IFAS Extension
I was lucky enough to spend a weekend in November exploring a lovely, low-key stretch of northwest Florida. We hiked trails and took the boat tour at Wakulla Springs State Park, marveling at the numerous alligators and admiring birds and a slow-moving manatee. We also hiked through St. Marks National Wildlife Refuge, which is home to a nearly 200-year-old lighthouse and keeper’s house, which have a fascinating history of their own.
The brilliant red, and edible, berry of the Carolina wolfberry is ripe in late fall/early December. Photo credit: Carrie Stevenson, UF IFAS Extension
Exploring the shoreline of Apalachee Bay behind the lighthouse, we watched fiddler crabs run the salt flats and herons quietly stalk their prey. Always on the lookout for something new, I noticed a large shrub growing several yards back from the beach. It looked like a cross between a rosemary and a holly, with delicate lavender/purple flowers and brilliant red teardrop-shaped fruit. I’d never seen it before.
Map of the natural range of Carolina wolfberry in Florida. Figure courtesy of the Florida Native Plant Society.
After a quick investigation, I learned it was a Carolina wolfberry, aka Carolina deserthorn, aka Christmas berry (Lycium carolinianum). The invasive species coral ardisia (Ardisia crenata) is also known in some areas as Christmas berry—this is why scientific names are so useful—but that is not the plant we saw at St. Marks. The native Carolina wolfberry was located right where you might expect it, on dry coastal scrub, in view of the saltwater it easily tolerates. Its native range in Florida starts along the coastline east of here, particularly Bay and Wakulla counties and all the way down around the state.
The delicate lavender flower of the Carolina wolfberry is a popular nectar source for native butterflies. Photo credit: Peggy Romfh
The tall shrub is evergreen, with leaves adapted into a long, thin, slightly succulent near-needle shape. This leaf form helps hold water in a dry, salty environment and prevents evaporation. The tips of the shrub’s branches have thorns, hence the common name “desert-thorn.” Carolina wolfberry produces those attractive little purple blooms in the fall, providing nectar for several species of native butterflies. In late fall/early winter, the brilliant red fruits show up. They are less than an inch long and reminiscent of peppers. When ripe, the fruit are edible and are described as sweet and tomato-like. The fruit are not only popular for human consumption, but also for birds, deer, and raccoons. Just before we walked down the beach, another visitor saw a bobcat disappear into the shrub, which provides cover for many additional species besides those who eat it directly.
Illustration from a 15th century plant medicine book showing the mandrake, a member of the Solanaceae family.
Carolina wolfberry is a member of the Solanaceae family, aka nightshade (sometimes referred to as “deadly nightshade”). Other relatives include edible tomatoes, peppers, potatoes, eggplant, and groundcherry. The “deadly” part refers to related species like belladonna and mandrake, from which toxic poisons can be extracted. If you’re looking for a fascinating historical deep dive into these plants’ connection to witches, Shakespeare, and the death of multiple Roman emperors, look no further than the US Forest Service’s web page on the “Powerful Solanaceae” family!
Doodlebugs create pitfall traps in dry, sandy areas to lure unsuspecting ants. Their “doodles” in the sand are visible as well. Photo credit: Carrie Stevenson, UF IFAS Extension
It’s been years since I ran across doodlebugs. But when I saw a stretch of their pitfall traps at a campsite near Coldwater Creek in MIlton, I knew it was time to write about them. Lore says their silly name came from Southern kids like me, who watched the larvae drag their bodies around in the sand, leaving patterns (or doodles) etched behind them. These insects have long fascinated children and creative writers, with some of my favorite authors–Twain, Steinbeck, Thoreau–referencing doodlebugs in their books.
Doodlebug larvae are pretty terrifying, with those giant killer mandibles. Photo credit: UF IFAS
Doodlebugs, aka ant lions (Myrmeleon immaculatus—although we have 22 species in Florida!), are fascinating little insects that prey upon ants by creating slippery funnels in the sand. They wait underground below the funnel opening as unsuspecting ants march along the surface and slide down in the ensuing “mini avalanche.” If an ant or other prey item manages to get away, the ant lion can sling sand at it to try and knock it back down into the pit. Doodlebug larvae are the stuff of cartoon nightmares. They possess a pair of giant clawed mandibles, capable of grabbing and injecting prey with a toxin. The poison paralyzes the victim and contains digestive fluids which liquify its insides. At this point, the ant lion goes in for the kill by sucking out the prey’s juices through its deadly mandibles.
An adult doodlebug/ant lion bears no resemblance to its larval stage! Photo credit: Campbell Vaughn, UGA
Ant lions may stay in this frightening larval stage for up to 3 years. After this they undergo metamorphosis, spending 3 weeks in a cocoon. As adults, their transformation is dramatic; they are closely related to lacewings and dobsonflies, with long, thin bodies and large translucent wings.
A doodlebug captures its prey. Photo credit: UF IFAS
As kids, we always found doodlebugs under my best friend’s treehouse. In Milton, they were in a sandy area beneath a cabin roof overhang. These dry, protected sand areas are their preferred habitat and the best place to find them. We used to stick pine needles down into the openings, and watch as a flutter of insect mouthparts tried to grab it from us. Because of their fascinating life cycle and dramatic hunting technique, doodlebugs can be a captivating addition to a science classroom. In fact, there’s a reference to doodlebugs on the NASA website, due to an Apollo 16 astronaut’s mention of them. When landing on the moon, the craters reminded Charlie Duke of doodlebug pits, prompting him to recite an old children’s rhyme, “Doodlebug, doodlebug, are you at home?”
The ornate passionflower attracts human and insect attention, alike. Photo credit: Mike Clark
There are some things in nature that look so bizarre, so beautiful, or so ornate that one can scarcely believe they’re real. This was how I felt the first time I looked closely at a passionflower (Passiflora incarnata) bloom. Between the deep shade of purple, the squiggly intricate filaments of the “corona” above the petals, and the bright green stigma and ovary, it seemed like something from the imagination of Dr. Seuss.
A Gulf fritillary butterfly visits the passionvine in my yard. Photo credit: Carrie Stevenson, UF IFAS Extension
Our vine is full of blooms right now, and every time I walk past the arbor I stop in admiration. I’m not the only one—the plant is covered up with Gulf fritillary butterflies, small orange and black near-mimics of monarchs. Like the monarch, they possess chemical defense mechanisms that make them taste bad to would-be predators. Fritillaries are so fond of passionvines as a nectar source that they are sometimes referred to as “passion butterflies.” Adult females frequently lay their eggs on the plant, as well.
Carpenter bees are big fans of the flower, digging for pollen throughout its bloom time. The leaves also attract pollinator insects; they have “extrafloral nectaries” that secrete a sugary substance at their bases, attracting bees and ants.
A carpenter bee visiting a passionflower. Photo credit: UF IFAS
Passionfruit are quite large for such a delicate vine—spherical, green, and about the size of a chicken egg. The plant is also known as a “maypop.” I’ve seen two explanations for this; the fruit’s skin is fairly thin, so it will respond with a satisfying “pop” if stepped on. Alternatively, the name could come from the idea that if the fruit drops into the soil and overwinters, a new vine will “pop” out of the ground the following May.
The passionfruit of the native Passiflora species. Photo credit: Mark Bailey, UF IFAS
The fruit is edible and has been prized for millennia as both a culinary and medicinal plant. Passion fruit juice has a strong, tropical flavor and contains fiber, vitamins A & C, and iron. It’s often used in jellies, ice cream, and other desserts. The pulp is edible raw, including the seeds. Most commercial production is in the equatorial regions of the world, particularly South America. Parts of Africa and Oceania produce it as well, along with more local sources in Florida, Puerto Rico, California, and Hawaii.
There are 500 varieties of Passiflora, with our native P. incarnata being one of the most cold-hardy of the varieties. The genus and common name “Passion” reference an early association of the flower with the crucifixion of Christ, with the flower parts imbued with symbolism and used by early Spanish missionaries to teach religious concepts to indigenous people in the Americas.
A red rat snake, or corn snake, slithers through the grass at a home in Pensacola. Photo credit: Cole Stevenson
It’s warm here in northwest Florida, which means our cold-blooded reptile friends are on the move. In the last few weeks, I’ve seen a snake at work, one at home, and received snake photos from my neighbors’ and parents’ yards. A fear of snakes seems to be both innate and passed down from one generation to the next. Cryptic by nature, snakes often surprise us when they appear in our path. Their lack of arms and legs feels creepy to us four-limbed mammals, and when you add in the fact that some of them are venomous, it’s a recipe for conflict. If I had a quarter for every time somebody told me, “the only good snake is a dead snake,” I could retire tomorrow.
So, I’m here to make the case for keeping good snakes alive. If you have spent any time around my colleague Rick O’Connor, you know he’s forever picking them up and singing their praises. It’s unlikely that you’ll catch me picking a snake up, but I’m definitely a fan of these fascinating creatures.
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Juvenile red rat/corn snake and a gray rat snake. Photos from the UF Snake ID guide, courtesy of Todd Pierson and Luke Smith.
Half the battle towards conquering a fear of snakes is knowing what you’re looking at. If you can recognize some of the most common nonvenomous snakes and realize which one is in your yard, it’ll take the edge off that first shot of adrenaline. The ones I hear of and see most frequently are garter snakes, black racers, and rat snakes. Rat snakes often have diamond patterned skin, but with practice it is easy to differentiate them from anything with venom. The Florida Museum of Natural History website has a really well done web-based snake identification guide categorized by pattern and using excellent photos.
A gray rat snake hiding out on a tractor. Photo credit: Carrie Stevenson, UF IFAS Extension
Members of the genus Pantherophis are more commonly known as the gray rat snake, (Pantherophis spiloides), red rat snake, aka corn snake (P. guttatus) and the Eastern or yellow rat snake (P. alleghaniensis). We see few Eastern rat snakes in the western Panhandle, but they often interbreed with the gray and red varieties. Full grown, ray rat snakes can grow to be anywhere from 3 to 7 feet long, whereas red rat snakes are usually no more than 4 feet.
Rat snakes are docile, with eye-catching color patterns. I recently came across a gray rat snake curled around a tractor tire at the 4-H property in Barrineau Park. Six of us were standing around within a few feet of it, but the snake ignored us, slowly winding its way around the equipment. At midday, it was resting in the shade and conserving energy. My kids and parents also had an interaction with a rat snake recently. As my son walked through his grandparents’ garage, he stepped on something “squishy” that felt like a hose or rope. To his surprise, it was a large red corn snake, lying right at the threshold of their door. Even after being stepped on, it was alert but not aggressive, slowly finding an escape route into the yard. Snakes generally avoid conflict when given the chance to leave on their own.
A healthy red rat snake in my parents’ garage fled at the sight of humans. Photo credit: Cole Stevenson
As their name implies, rat snakes are known for feeding on rats and mice. They perform an important community service, if you will, keeping the population of vermin in check. They also eat insects, frogs, and birds. Rat snakes are constrictors, but will eat smaller prey whole and alive.
Snakes play an important role in the ecosystem, serving as both predator and prey for many animals. They are in the business of hiding most of the time, and would rather not see people. If you do have a lot of unwanted snake interactions on your property, there are several things you can do to reduce their likelihood, like sealing gaps in buildings where snakes can hide and keeping brush piles well away from a home. But the easiest thing is to observe them from a distance and let them go about their day. While any wild animal will bite in self-defense, the odds of being bitten very low if you don’t harass or try to pick one up!
