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.
Before my career in Extension, I spent ten years selling plants. I worked at a 40-acre nursery that was filled with thousands of plants. The selection was enormous and it was an eye-opening experience, even for a horticulturalist, to see how many different types of the same plant species were on the market. I learned quickly that if someone came in and said, “I need a daylily,” “I need a hydrangea,” or “I need a loropetalum” there were a lot more questions that needed to be asked to help them properly!
Plant breeders in ornamental horticulture spend their careers selecting plants for winning features that gardeners will line up to buy. Examples of traits include flower color, repeat flowering, mature size, disease resistance, cold hardiness, sun/shade tolerance, and foliage color. There are a lot of steps between recognizing what might be a superstar and availability in your local garden center, but let’s just jump to the part where they are in the garden center.
When shopping for plants, always look for the full name of the plant, preferably the botanical name which will include genus and species in Latin. Some plants are grown from seed and may have some variation in features. For example, a live oak grown from an acorn will be named with only genus and species, Quercus virginiana. The mature growth habit will have a wider range than one that was cultivated from a parent plant with known features. The species could be smaller than average, larger than average, an interesting branching feature, etc. Think of your own family, kids from the same parents may have different eye color, hair color, and height but they are all human children!
A cultivated plant is grown from cuttings or similar propagation methods that create a genetic clone of the originally selected plant. It is considered a cultivar if it will not grow true from seed and needs human intervention to result in the identical characteristics as the parent plant. The botanical name of a cultivated plant will follow the italicized species and is written/typed in single quotes. Note, since many plants are trademarked, there may be a botanical name that isn’t very flashy followed by a similar name, with some marketing flair. Let’s look at a couple of examples:
Pictured here is Emerald Snow and Purple Pixie Loropetalums. Their foliage color and sizes are very different.
Loropetalum chinense ‘Shang-white’ PP21738 is the official botanical name for Emerald Snow® Semi-dwarf Loropetalum. Emerald Snow® is a green-leaf, white flower semi-dwarf loropetalum that will reach 4-6’ tall by 3-5’ wide.
Loropetalum chinense ‘Peack’ PP18441 sold commercially as Purple Pixie® Dwarf Weeping Loropetalum has red foliage, pink flowers, and matures at 1-2’ tall by 3-4’ wide.
As you can see, just asking for a Loropetalum can result in vastly different plants!
Relying on common names only can also lead to an unintentional purchase. The same common name may be used for two very different plants. Another issue is that closely related species may have different places of origin and if you are trying to use only Florida native plants that could impact your design plans. Here are a couple of examples:
Mock orange may refer to deciduous weeping shrub with white flowers that performs well in cold climates, Philadelphus coronarius, or an evergreen shrub that is only hardy to Zone 8a, Pittosporum tobira.
Beautyberry can be native to Florida or other areas of the world. Callicarpa americana is native to North America, including Florida. Callicarpa japonica is native to China and East Asia.
The takeaway message is always look for botanical names and do a little homework when purchasing plants. Ensure the plant you are looking at has the features that match your landscape needs!
In the late 1700’s, explorer and naturalist William Bartram and his father, the “King’s Botanist”—visited Pensacola and much of the southeastern United States. Curious observers of everything from plant growth and wildlife to Native American culture, they were also collectors. Countless American plant species were sent to Europe for further examination and later preserved in gardens and arboretums.
The Franklin tree no longer grows in the wild, but was originally discovered and named in the late 18th century near this spot in coastal Georgia. Photo credit: Carrie Stevenson, UF IFAS Extension
If it were not for their formidable observation skills, at least one species of unique native tree would be completely extinct. While traveling along the Georgia coast in 1765, the Bartrams recorded and named a species of small tree they’d never seen anywhere before. They christened it the “Franklin tree” for their friend and compatriot Benjamin Franklin. Known scientifically as Franklinia alatamaha (after Franklin and the nearby Altamaha River), its similarity to the loblolly bay tree landed it in the Gordonia genus for a while. References in the literature to this tree may include Gordonia alatamaha, Gordonia pubescens var. subglabra, or Lacathea florida, although it is now officially Franklinia alatamaha and considered part of the tea tree family.
The attractive bloom of the Franklin tree is reminiscent of magnolia flowers. Photo credit: Scott Zona, used with permission from NCSU Extension
William Bartram knew this species was unique, as he never saw the tree elsewhere in any of his extensive travels. He returned to the area in 1776, this time collecting seeds from the Franklin trees and propagating five of them successfully back at his home in Pennsylvania. The last time this species was seen in the wild was at the original wetland floodplain along the Altamaha River between 1790-1803. Now, the only Franklin trees in existence are all descendants of the seeds collected by William Bartram.
A sign in the Brunswick, GA marine extension office/demonstration garden explains the tree’s unique history. Photo credit: Carrie Stevenson, UF IFAS Extension
Their exact cause of extinction is not clear, but there are some solid theories. Land adjacent to the river was cleared for cotton farms, and the Franklin trees were vulnerable to a fungal pathogen that affects cotton. Based on the early records, the very small endemic population was particularly susceptible to habitat destruction and changing climatic conditions.
While no longer growing in the wild, the tree is mostly living in demonstration gardens and Arboretums on the east coast. However, it can be found in the nursery trade and grown in a large swath of the country if cared for properly. I was introduced to this species for the first time at the Brunswick, Georgia marine extension office. In addition to working with fishermen, they also educate residents on native landscaping and ways to prevent stormwater runoff and pollution. Over a span of a few years, they transformed the “front yard” of their office building from a turf lawn with a couple of oaks to a lush landscape full of flowers, shrubs, and pollinator insects. Included is a Franklin tree, with signage explaining its unique history. At about 15-20 feet tall, it has reached mature height. The original site of the Bartrams’ discovery is less than 20 miles from the garden location.
Just a few years ago, this lush garden consisted only of turf grass and a few live oak trees! Photo credit: Carrie Stevenson, UF IFAS Extension
Plant names in today’s industry are not as simple as the established binomial (genus and specific) and a common name. Many of the plants that you get for your landscape are varieties, cultivars, and hybrids. To make matters more complicated, there are trade names that are given to plants to aid in marketing. We see the Endless Summer® hydrangea or Purple Pixie® Loropetalum. Throw into the mix the work of plant taxonomists who are always reclassifying plants and we can all be truly confused about a plant’s name.
Even as names change, it is still fun to learn plant names. Just recently, I sent plant pictures to the UF Herbarium to help get a clarification on the plant I was calling Georgia savory, Clinopodium sp. This is one of my favorite plants because it makes a spreading groundcover that grows about 1.5 feet tall and has tubular flowers in spring and fall. Many pollinators visit the flowers. It also grows well in sandy, well drained soil and thrives on occasional water. I have a single plant in my backyard that only gets water from rain and has grown to five feet wide over several years. It is definitely a low maintenance beauty.
My results back from the UF Herbarium did not completely clear up this plant’s name. There are reports that it is a hybrid of Clinopodium georgianum × Clinopodium ashei ‘Desi Arnaz’. Other information suggests that it is an intergeneric hybrid between Clinopodium and Conradina named x Clinadina ‘Desi Arnaz’.
The lesson from all this confusion is to just do your best. Realize that all of us can be mistaken on a plant’s name and even those that study plants in depth don’t always agree on a name. In the world of plant names, change can happen.
Most of us are familiar with the Appalachian Trail, the popular hiking route that follows the mountains from Maine for nearly 2,200 miles to north Georgia. But did you know you could set off from Fort Pickens at Pensacola Beach and follow the Florida Trail for over 1,100 miles, all the way to Big Cypress in the Everglades?
The statewide Florida Trail begins at Ft. Pickens! Photo credit: Carrie Stevenson, UF IFAS Extension
Inspired by the Appalachian Trail in the 1960’s, Florida Trail Association founder James Kern started gathering support and planning a route for a Florida trail that would take a trekker through nearly the entire length of the state. By 1983, the Association’s efforts resulted in recognition as a National Scenic Trail, with the path currently winding through the property of over a hundred land management partners. Some stretches of the trail are designated for biking or horseback riding, but the vast majority are intended for foot traffic only. A through-hike of the Florida Trail can be challenging, as the weather, water, and insects can be more intense in our climate than cooler areas. Dozens of people complete the journey every year, and the trail is gaining in popularity. In 2020 and 2021, fewer than 20 individuals were certified as through-hikers. However, last year 47 individuals signed the end-to-end hiker roster online, complete with their “trail name” and hometown. Many hikers are Floridians, but more than half the roster included people from other regions of the United States, and even a couple from Germany.
A brick sign echoes the architecture of Ft. Pickens along the trail at the northern end of the Florida Trail. Photo credit: Carrie Stevenson, UF IFAS Extension
At the northern terminus of the trail adjacent to Ft. Pickens, hikers will experience a relatively flat, sandy path along the dunes. A bridge crosses a small freshwater pond, then the trail leads to shadier secondary dunes. On a hike this past October, I saw plenty of blooming fall wildflowers, a turtle, a frog, and numerous birds. The Blackwater Side Trail along Blackwater River State Park and Forest consists of a totally different ecosystem, with 48 miles of shady and hillier terrain. This particular stretch connects with the Alabama Trail, which is still being linked together but aims to run the entire north-south length of the state. According to those who have hiked the whole Florida Trail, the most challenging sections include mucky soil through Big Cypress and rocky, uneven limestone and grasses in south Florida. There are plenty of interesting sights and potential hazards, from alligators and black bears to flooded trail routes and pop-up thunderstorms. But the rewards are vast, too, like having the whole trail to yourself most of the time, with opportunities to see rare panthers and a 2,000-year-old cypress tree. Interested hikers can reach out to the Florida Trail Association’s Western Gate, Choctawhatchee, or Panhandle Chapters if you have questions, (including local member Helen Wigersma). These groups help maintain sections of the trail and are a wealth of information. If you’re up for a new adventure this year, you can start a real one right here in our backyard.
Florida Trail map with alternate routes, provided by the Florida Forest Service. https://www.fs.usda.gov/main/fnst/maps-publications
Twigs dangle from a branch, held in place by horsehair fungus rhizospheres. Photo credit: Carrie Stevenson, UF IFAS Extension
Imagine walking through the woods, enjoying the fresh air and birdsong, when you notice a twig just dangling midair. On first glance, you might presume it is stuck in a vine or a large spider web. However, this material is thinner than a vine and there are no spiders or webs to be found. On closer inspection, you see the twig is entangled in a dark knot of string, slightly thicker than a human hair. Following the source of the black string leads to a lacy network of the same material, flat against and around the branch from which the twig hangs. Fifteen feet down the trail, you come across the same thing—more twigs hanging from “string” in the trees, dangling from a knot of thin black material. What is going on here?
After some research, my conclusion is that we have come across horsehair fungus (Mirasmius spp). Mushrooms and other fungi have long, thin, rootlike structures called rhizomorphs. Rhizomorphs are composed of large numbers of microscopic hyphae, which are tubular and exchange nutrients and water among other parts of the fungus. The hyphae are typically located underground, but in this instance, they are visible in the open.
The ropy network of rhizospheres is visible on the branch, then turns into thin fibers that can trap plant debris. Sample provided by Suzy Marshall.
Aerial rhizomorphs are an excellent example of an evolutionary strategy known as resource partitioning. By forming a netted trap to intercept falling leaf material on a tree, the fungus gets a jumpstart on the decomposition process, taking nutrients from dying plant material before it falls to the ground. The tree-dwelling fungus is thus not competing directly with fungi on the ground, and both types of fungi can thrive. In human terms, this is loosely analogous to co-workers labeling their own food in a shared refrigerator. Everyone eats, but no one has to compete with another for nutrition.
A bird’s nest in Argentina is composed primarily of strong horsehair fungus fibers. Photo credit: Danny Newman
The common name, “horsehair fungi” applies to many species around the world. They are most common in nutrient-poor subtropical and tropical forests, where any available nutrients in the soil are used up quickly by the lush tree growth. They can be found here along the Gulf Coast, up to the Appalachian Mountains, and as far away as equatorial rainforests. In a Malaysian study, researchers found that the aerial fungi trapped up to 225 pounds of fallen plant material per acre! This network of material also supported a significant population of arthropods, which were crucial parts of the overall ecosystem by providing pollination, herbivory, and serving as detritivores. One study of spruce-fir forests in the northeastern United States showed that birds are known to use the material as a nest lining, as it is lightweight but very sturdy. In this particular research, 85% of the nests (particularly of warblers and thrushes) examined utilized the material.
