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What are plant galls?

Created 10 Jul 2026 · Updated 24 Jul 2026

Plant galls are abnormal growths that form on plants, induced by organisms who want to redirects the plant's normal development. They can be induced by insects, mites, fungi, bacteria, viruses, nematodes, and many others. The inducers effectively hijack the plant's developmental program to create structures and functions that provide food, shelter, or a protected environment for them. Spotted Oak Apple Gall. (Image by Lora Shadwick).png

(Image by Lora Shadwick)

Visually, galls are remarkably diverse (see Galls Gallery). Some are smooth sphere shape, others sometimes resemble fuzzy pink pom-poms, woody tumors, spiny capsules, or sculptural forms unlike any ordinary plant organ. They vary widely in size, color, texture, and internal structure, making them some of the most unusual growths found in nature.

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