What Is a Gall?

Get the facts on galls and why they form on plants.
By: Marie Hofer
Related To:
p_gall

p_gall

Abnormal growths that appear on the surface of leaves (or stems) are usually a sign that an insect is at work. There are hundreds of gall types, caused by mites, midges, tiny wasps, aphid-like insects and thrips and they vary in shape — from red and spindly to round and green to large and woody — depending on the type of insect and the plant affected.

A gall forms as a reaction between chemicals produced by the female insect and hormones produced by the plant. Sometimes the insect expresses those chemicals when she lays eggs on the plant part. The plant reacts by developing abnormal tissue.

To the insect, the gall offers protection — a kind of womb. The eggs hatch inside, and the young insects later emerge, sometimes after having fed on material inside the gall. With the elm pocket gall, a female mite injects saliva into the leaves, initiating the formation of elongated red galls, and other mites enter the galls from the underside of the leaf.

Galls in ornamental trees cause little damage except for aesthetics. No treatment is usually necessary. If treatment seems called for, a dormant oil spraying is usually effective, but this must be done before bud break.

The grape phylloxera is all too familiar to grape growers, however. The round galls formed on leaves are a benign problem, but galls that form on the roots can cause stunting and death of the plant.

Keep Reading

Next Up

Lasagna Gardening

Layer bulbs this winter for a spectacular spring show and bake up a tantalizing succession of color and fragrance that will last for months.

Wildflower Gardening

Love wildflowers? Create a meadow using these tips as a guide.

Understanding How Plants Grow and Reproduce

Whether you choose posies or poppies, it's important to know the specifics about a plant's various growth stages.

Control Vine Growth

Use these tips to grow eye-catching vines outside your home.

Silver Bush Lupine

Master gardener Maureen Gilmer gives a primer on growing bush lupine.

A Guide to Growing Apples

Perhaps the most classic fruit, apples are a bountiful crop when given proper attention and care.

Tips for Fertilizing Garden Plants

Help your garden thrive with these easy ideas for feeding plants.

Beverage Garden

Spritz up your drinks with sprigs from the herb garden.

Button Mums

Discover the versatile—and tough—blooms of button mums.

Herbal Home Remedies

Growing herbs is fundamentally about using them in ways that are natural and beneficial to your health and general wellbeing. Learn about some basic herbal home remedies and their aftercare.

1,000+ Photos

Browse beautiful photos of our favorite outdoor spaces: decks, patios, porches and more.

On TV

Caribbean Life

7:30am | 6:30c

Flip or Flop

12pm | 11c

Flip or Flop

12:30pm | 11:30c

Flip or Flop

1pm | 12c

Flip or Flop

1:30pm | 12:30c

Flip or Flop

2:30pm | 1:30c

Flip or Flop

3:30pm | 2:30c

Flip or Flop

4:30pm | 3:30c

Flip or Flop

5:30pm | 4:30c

Flip or Flop

6:30pm | 5:30c

Flip or Flop

7:30pm | 6:30c
On Tonight
On Tonight

Flip or Flop

8pm | 7c

Flip or Flop

8:30pm | 7:30c

Flip or Flop

9:30pm | 8:30c

House Hunters

10pm | 9c

House Hunters

11pm | 10c

Flip or Flop

12am | 11c

Flip or Flop

12:30am | 11:30c

House Hunters

1am | 12c

Flip or Flop

3:30am | 2:30c

Follow Us Everywhere

Join the party! Don't miss HGTV in your favorite social media feeds.