Fall webworms in a Tennessee forest. Photo credit: UF IFAS Extension
Have you ever noticed the big knots of webbing in some trees this time of year? They’re usually sort of a brown-pink hue, much too big for a spider but not really tightly wound enough to be a nest or cocoon.
A close-up of the fall webworm tent reveals dozens of tiny caterpillars and skeletonized leaves. Photo credit: Carrie Stevenson, UF IFAS Extension
What you’re seeing actually is a cocoon of sorts—a big shared one created by hundreds of larval fall webworms (Hyphantria cunea). This common name is a bit of a misnomer. The webbing—often referred to as a tent—is built in late summer, not fall, and these are caterpillars, not worms. But I suppose it gets the idea across!
On a recent hike, I saw webbing up close, so I was able to really investigate the caterpillars inside. They are quite small, and will undergo up to five molting stages, or instars, before adulthood. Upon transformation, they will become white or speckled moths. Fall webworms are native to the entirety of the United States—in the northern end of their range the moths will be solid white, whereas further south they will have darker spots on their wings. Due to accidental introduction, fall webworms are invasive throughout Europe and portions of Asia.
Adult fall webworm, with spots on white, which is typical for members of this species from the southern part of its range. Photo credit: Lyle Buss, UF
Host plants include a wide range of more than 80 deciduous hardwood species, allowing a broader spectrum of places for the caterpillars to undergo their various larval phases. During their months in the “tent”, the larvae feed on and skeletonize the leaves encapsulated within their webbing. This causes damage to the leaves, but results in no permanent issues to the trees—being late summer and fall during their tenure, the trees eventually lose their leaves anyway.
While the tents are a bit unsightly, controlling the caterpillars or removing the webs is unnecessary. Once they’ve reached their final caterpillar stage, they’ll hide out in tree bark and leaf litter on the ground until metamorphosizing into moths the following spring. Adult moths mate and lay eggs in the late spring and summer, starting the cycle all over again.
In the garden, mistletoe is not a plant we want to see. This parasitic plant can cause issues for some of our trees and we need to address the issue when we are able. Learn more about mistletoe in our landscape plants with UF IFAS Extension Escambia County.
Red Maple in flower. Photo courtesy of Carrie Stevenson.
A month ago, when the Panhandle was covered in snow, it would have been hard to imagine that spring was just around the corner. But warm spring weather has arrived, and with it, the first of our native trees to bloom each year – the venerable Red Maple (Acer rubrum). Reliably heralding spring in Northwest Florida each February, Red Maples adorn our roadsides and low-lying natural areas with brilliant red blooms. Spotting a Red Maple blooming amongst the otherwise drab landscape means winter is on its way out and spring has sprung – or will shortly.
Beyond the blooms, Red Maple has much to offer as a landscape tree. For one, it is unbelievably adaptable. Across its native range – one of the most expansive of any species in the US, occurring naturally from Maine all the way down to the Everglades,* the tree can handle soils that range from periodically inundated along streams and other wet areas to more well-drained upland sites. Adding to its adaptability, in the Panhandle, Red Maple typically tops out around 40’ in height and around 20’ wide with a spreading vase shape, rarely growing out of scale with most landscapes.
*Since Red Maple occurs over a huge area of the US, it’s important to purchase seedlings or named varieties that hail from areas with like climate conditions to the Panhandle. Avoid varieties from northern states for best performance.
Red Maple is one of the few shade trees that has true four-season interest in our area. We’ve already talked about its spring flowers, but it also has attractive deep green foliage in the summer (some selections, like ‘Summer Red’ are even known for reddish purple new growth), famous fall color (though it is more muted in Florida than locales farther north), and unique ridged light gray bark in the winter. The seeds of Red Maple are even pretty. These two-winged seed structures, called a samara, follow the spring flower show, appear pinkish red, and are a favorite of squirrels and other critters.
Red Maple samaras. Photo courtesy of Daniel Leonard.
Red Maple is a quick growing, low maintenance tree as well. If planted correctly and properly cared for, the species can grow several feet per year in its youth. Site the tree in a moist site that receives full sun, plant slightly higher than the soil level of the container the tree was purchased in to compensate for soil settling post-planting, and water regularly until established. After establishment, periodic fertilizing with a balanced fertilizer will help ensure Red Maple’s nutritional needs are met and maximum growth achieved.
If you’ve been looking for a medium-sized, native, flowering shade tree with four-season interest, Red Maple may be just the tree for your landscape. Plant one today! For more information on Red Maple, other recommended landscape plants, or any other horticultural topic, contact your local UF/IFAS Extension office.
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.
