Spiky, round objects scattered across lawns often pique curiosity about their origin. This article identifies the specific tree that produces these distinctive balls, explores their biological function, and considers other trees with similar-looking fruits.
The Sweetgum Tree
The American sweetgum tree (Liquidambar styraciflua) is the most frequent source of these spiky balls. This deciduous tree is widely distributed across the southeastern United States, extending into Mexico and Central America. It grows in moist, well-drained soils and is commonly planted in urban and suburban areas for its aesthetic appeal and shade.
Sweetgum trees have several recognizable features. Their leaves are star-shaped, with five to seven pointed lobes, and are glossy green during the warmer months. While these leaves might sometimes be mistaken for those of maple trees, sweetgum leaves grow alternately along the stems, differentiating them from maple’s opposite arrangement. The bark of mature sweetgum trees is gray-brown, rough, and deeply furrowed, with younger branches sometimes displaying corky ridges or “wings.” These trees commonly grow between 60 to 100 feet tall, with some specimens exceeding 130 feet in wild conditions.
Unpacking the Spiky Balls
The spiky balls, often called “gumballs,” are the dried, woody fruit capsules of the sweetgum tree. These spherical structures are 1 to 1.5 inches in diameter and mature from green to a dark brown color as they dry. Their purpose is seed dispersal, as each capsule contains numerous small, winged seeds.
The fruit consists of many individual capsules clustered together, each with small projections that contribute to the overall spiky texture. These capsules open along seams to release their seeds after falling from the tree, usually from late fall through winter. The spikiness protects developing seeds from consumption by certain animals and assists in dispersal by allowing the fruits to cling to animal fur or roll with the wind. Each gumball can contain up to 50 seeds.
Other Trees with Spiky Fruits
While sweetgum is a prominent producer of spiky fruits, other trees also yield similar burr-like structures. The Horse Chestnut, or Buckeye (Aesculus species), produces fruits encased in a thick, leathery husk that can be prickly or warty. This husk splits open to reveal one or more large, smooth, shiny brown nuts, which are distinct from sweetgum’s many small seeds and are toxic to humans. Unlike sweetgum’s uniformly spiky ball, the Horse Chestnut’s fruit has more blunt spines and is generally larger.
Another tree known for its spiky fruits is the American Chestnut (Castanea dentata). Its burrs are densely covered in sharp, needle-like spines, making them quite formidable to handle. These burrs are typically larger than sweetgum fruits and, upon ripening, split to release two to three edible chestnuts. The distinct appearance of these nuts and the very sharp nature of the chestnut burrs help differentiate them from the sweetgum’s woody capsules.
Living with Spiky Balls
The abundance of sweetgum balls dropping from trees can create practical challenges for homeowners and land managers. These hard, spiky objects can pose a tripping hazard on walkways and lawns, potentially causing falls. They are also known to be painful to step on, especially barefoot, and can damage lawnmowers or clog lawn vacuums, making cleanup difficult. Their persistent presence often necessitates regular raking or other collection methods to maintain clear areas.
Despite being a nuisance in landscaped areas, sweetgum balls fulfill an ecological role. The seeds within the capsules provide a food source for various wildlife, including squirrels, chipmunks, and several bird species like finches and ducks. The tree itself offers habitat and shade, contributing to local ecosystems. For those managing properties with sweetgum trees, options include regular cleanup, or, for new plantings, selecting fruitless sweetgum cultivars, which offer the tree’s beauty without the prolific fruit drop.