Some are pinned to leaves like delicate jewel brooches, whereas others are disfiguring bulbous growths that squat on plants like alien invaders. Galls — abnormal growths on plants and trees caused by parasitic organisms — are among the most intriguing of Nature’s creations and can be both beautiful and horrifying.

The charming cherry gall, for example, adorns oak leaves with delicately speckled red baubles and the unseemly horned oak gall wraps itself around branches like the clawed toes of a hideous monster. All capture the imagination and all are formed from the plant’s own tissue, altered by physical injury or alchemised by chemical secretions.

The most common culprits are invertebrates: often tiny gall wasps, less than half an inch in length, or flies, mites and aphids. As aphids nib

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