If you’ve ever noticed small, round, and woody brown balls on trees in your yard or on a walk, you’re not alone. These curious growths are a common sight and often spark questions about what they are and if they’re harmful. Let’s clear up the mystery and give you the practical knowledge you need as a gardener.
These woody balls are almost always plant galls. They are not a fruit or seed, but a reaction to a tiny invader. Most often, an insect, mite, or fungus triggers the tree to grow this extra tissue. Think of it as the tree’s version of a protective scab. The gall forms a home and food source for the creature inside, while isolating it from the rest of the plant.
Brown Balls On Trees – Small, Round, And Woody
While “gall” is the general term, the specific appearance—small, round, woody, and brown—points to a few usual suspects. The good news is that the vast majority of galls are cosmetic issues and cause little to no lasting harm to healthy, established trees. Your tree might look a bit odd, but it’s rarely in danger.
Common Trees Where You’ll Find These Galls
You can find galls on many trees, but some species are more prone to specific types. Here’s where you’re most likely to spot those characteristic brown balls:
- Oak Trees: The undisputed champions of gall diversity. Oaks can host hundreds of gall types.
- Maple Trees: Often get round, woody galls from mites.
- Hackberry Trees: Frequently develop “Hackberry Nipple Galls” on their leaves.
- Willow and Poplar: Can also form various stem and bud galls.
The Most Likely Culprits: Insect and Mite Galls
Most of the galls you see are created by very small organisms. Here’s a breakdown of the main creators:
Gall Wasps (Cynipidae)
These tiny, harmless-to-people wasps are the master architects of the oak gall. The female lays an egg into a leaf bud or stem, and the tree’s reaction forms the gall. The larva lives safely inside, feeding on the gall tissue until it matures and chews its way out. The “Oak Apple Gall” and “Oak Marble Gall” are classic examples of their work.
Eriophyid Mites
These microscopic mites are too small to see without magnification. They feed on plant cells, causing the tree to produce abnormal growth. Their galls are often very uniform and round, like the “Maple Bladder Gall” which starts red and turns brown and woody.
Midges and Flies
Some small flies and midges also induce gall formation. Their galls can be found on stems, leaves, and buds of various trees and shrubs.
Fungal Galls: A Different Kind of Problem
While less common for the classic “round woody ball,” fungi can cause growths like Black Knot on plums and cherries, which is darker and more irregular. A more relevant fungal issue is cedar-apple rust, which causes hard, woody galls on cedar trees that produce gelatinous horns in spring.
Should You Be Worried? Assessing the Damage
In most cases, no. Galls are a fascinating example of nature’s complexity, not a crisis. Consider these points:
- Health Impact: A healthy tree can support many galls without any significant impact on its overall vigor or lifespan. The gall actually confines the damage to a localized area.
- When to Concerned: Only be concerned if a very young, newly planted, or already stressed tree is completely covered in galls. This rare occurence could stunt growth or contribute to decline.
- Aesthetic Damage: This is the primary “harm.” Galls can make leaves look bumpy or cause clusters of twigs to form (witch’s broom galls).
Practical Management: What to Do (And Not Do)
Your response should be calm and measured. Reckless action often causes more harm than the galls themselves.
Step-by-Step: What You Can Do
- Identify the Tree and Gall: First, figure out what tree you have. Then, examine the gall’s shape, size, and location. A local extension service website is a great resource for photos.
- Practice Good Tree Care: The best defense is a healthy tree. Ensure it gets appropriate water (especially during drought), mulch properly, and avoid injuring the trunk with lawn equipment.
- Prune Selectively: If a few branches are heavily infested and it bothers you, you can prune them off in winter when the tree is dormant. Dispose of the galls in the trash, not the compost.
- Accept Nature’s Process: Often, the best action is inaction. Natural predators like birds and other insects will often control gall-makers over time.
What to Avoid
- Do Not Spray Insecticides: By the time the gall is visible, the insect inside is protected by the woody ball. Sprays are ineffective and will harm beneficial insects that keep other pests in check.
- Don’t Panic and Remove the Tree: This is drastic overkill for a problem that is mostly visual.
- Avoid Heavy Fertilizing: Excess fertilizer can sometimes stimulate succulent growth that attracts more pests.
Prevention for Next Season
Since most galls start from eggs laid in buds, prevention is tricky. However, for certain recurring problems on small trees, horticultural oil applied in late winter (dormant oil) can smother some overwintering eggs before they hatch. Timing is critical for this to work, and it’s not a guarantee.
Remember, a tree with galls is usually a sign of a diverse ecosystem, not a failing one. These structures provide food and habitat for other wildlife. By understanding them, you can appreciate a small part of your garden’s complex web of life.
FAQ: Your Quick Questions Answered
Q: Are the brown balls on my tree a type of seed or fruit?
A: No. They are abnormal growths called galls, caused by a reaction to an insect, mite, or fungus. They do not contain tree seeds.
Q: Can these round woody galls kill my tree?
A: It is very unlikely. Healthy, mature trees tolerate galls well. Only severe infestations on very young or already dying trees are a concern.
Q: What is inside the small brown ball on the tree branch?
A: Usually, you’ll find the developing larva of a tiny wasp or fly, or a colony of microscopic mites, depending on the gall type.
Q: Should I pick the galls off my tree?
A: Not usually. Picking them off by hand is impractical and can damage the tree. Pruning a few affected branches in winter is a better option if you must.
Q: Do galls spread from one tree to another?
A: The organisms that cause galls can move to nearby trees of the same species. But the galls themselves are not contagious like a disease; each gall forms individually in response to an egg or feeding.
Q: Are galls the same as burls?
A: No, they are different. A burl is a large, woody, rounded growth usually caused by stress or injury, not a specific insect. Burls are part of the tree’s trunk or branches, while galls are smaller and often on leaves or twigs.