Guide

Look closerFungi

Cedar-apple rust galls on red cedar and juniper

October to March

Look at the twigs of an eastern red cedar or other juniper for woody, brown, dimpled balls. They are galls made by the cedar-apple rust fungus, and after warm spring rains a mature gall can sprout orange, jelly-like horns.

Why this time of year

The dormant galls sit bare and brown on the twigs through the cold part of the year, so you can find one before the spring horns show. Find one and you can come back to the same tree after a warm spring rain.

How to notice it

  1. Pick an eastern red cedar or other juniper along a yard edge, field edge or roadside path.
  2. Scan the twigs for round, brown, woody lumps that look dimpled, like a tiny golf ball. Most are about a quarter inch to 2 inches across, and some are bigger.
  3. Look closely at the surface: before the spring rains it looks rather smooth, with small dimples where the horns will come out.
  4. Note the tree, then return after a warm spring rain to see whether orange, jelly-like horns have swollen out.

Try this with kids: Can you find a brown ball on a cedar twig? How many dimples can you count, and what do you think will grow out of it?

Word to know: A “gall” is a swelling that forms where a plant is infected, here by a fungus.

Sources

  • umass.eduUMass Extension (primary, regional): 'Junipers and redcedars harboring the pathogen develop 0.25-2 in. diameter, rounded galls on infected needles and small twigs'; galls secrete orange-brown gelatinous tendrils in wet mild spring weather, roughly mid-April to mid-May in southern New England; advises 'Prune dormant galls from junipers during the fall, winter and early spring' before tendrils form.
  • mdc.mo.govMissouri Dept of Conservation (state agency): 'On cedars, this rust forms brown or purplish, rather woody, dimpled long-lasting galls on twigs'; width 'often to more than 2 inches, not including the orangish protrusions'; galls look smooth until wet spring weather triggers the orange horns; horns swell in wet weather and can rehydrate after drying. Also: 'Some people think they look like lumpy brown golf balls'; dried horns 'shrivel and shrink to look like rusty, crusty spines'.
  • hgic.clemson.eduClemson Extension (university): young galls are 'small brown growths that are covered in ring-shaped indentations'; mature galls produce 'bright orange, gelatinous telial horns'; up to 2 inches in diameter. Does not state winter persistence.

Checked against these sources on October 13, 2026.

In the guide for October, November, December, January, February, March

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