What Is Mossy Rose Gall? Fuzzy Growths on Rose Bushes

Are you witnessing strange, fuzzy, colorful growths on your roses? Are you worried about the health of your rose and its neighboring garden plants? If you live in the U.S., you may be one of the few affected by mossy rose gall. In this article, gardening expert Taylor Sievers discusses this peculiar garden phenomenon. Spoiler alert: the answer may not be what you think!

Close-up of a Mossy rose gall on a rose bush against a blurred green garden background. Mossy rose gall appear as abnormal growths on rose plants, resembling small, moss-covered balls. This gall is a rounded structure covered with a moss-like coating of a reddish-green color.


You may have encountered a peculiar fuzzy substance growing on your rose bush in past seasons or maybe even this season. What is this thing that looks like it stepped out of a Dr. Seuss book? Is it nature, or did my neighbor spray something funky nearby? Is it poisonous or can I touch it (and maybe pet it?–just curious). Am I going to lose all of my roses?

Never fear! You’ve likely encountered a rose gall. This garden peculiarity is something rosarians worldwide have encountered for hundreds of years.

It’s normal to question what’s going on when your plant experiences something unusual. Let’s dive into mossy rose gall (also known as rose bedeguar or Robin’s pincushion) so you can feel confident in the future about handling this disease that really isn’t a disease.

The Short Answer

Mossy rose gall is a swollen growth that occurs on the stems of roses. New galls are greenish to reddish and furry or mossy in appearance. Old galls are grey-brown and crunchy. The galls are not the result of a disease (like these common rose diseases), but rather the result of the cynipid wasp (Diplolepis rosae) laying their eggs inside the buds of roses. The eggs will hatch inside chambers of the gall and then exit the following season.

The Long Answer

Let’s dig deeper into what causes galls to form, if they affect overall plant health, which roses are most susceptible, how to deal with the galls, and a common look-alike. Oh, and there’s some really weird historical facts about this phenomenon, too!

What Causes a Gall to Form on a Plant?

Close-up of Gall wasp on a red leaf. This small insect is brownish-black in color. Its appearance features a stout body with prominent antennae and wings.
Cynipid wasps induce gall formation by laying eggs.

Galls form because of the interaction between two living organisms, typically a plant and an insect, disease, or mite. When the affecting organisms burrow into the plant or infect the tissues, it causes the plant to change its normal growth.

The cynipid wasp female uses its ovipositors to insert eggs into leaf buds of the roses in the spring. This initiates gall growth. Research shows that the larvae later produce chemicals to continue gall formation.

The tissues swell around the gall maker. With the cynipid wasp, the gall provides protection from weather, parasites, and predators. Basically, the gall ensures the eggs and larvae live a sheltered life.

Galls are often rich in proteins and carbohydrates, so the larvae are also being enriched by the casing, as well. Eventually, the larvae of the cynipid wasp pupate and emerge out of as an adult wasp, usually in the spring or summer. The Diplolepis rosae adult wasps are usually females and ready to lay eggs quickly–no male needed.

The galls are typically one to two inches in diameter, depending on the number of larval chambers within the gall. Each chamber contains a single larval wasp. More eggs equals a larger gall.

Do Mossy Rose Galls Affect Overall Plant Health?

Close-up of a rose bush with Mossy rose galls. Mossy rose gall, caused by the gall wasp Diplolepis rosae, manifests as distinctive abnormal growths on rose bushes, appearing as small, spherical clusters covered in a moss-like texture. These galls vary in size and are found on stems or branches of the rose bush. They are raised, round growths, initially red-green in color, but developing a mossy or fuzzy exterior as they mature.
These strange formations are unsightly but don’t harm roses significantly.

Although they look alarming, these galls do not affect the overall health of your rose. The galls are simply unsightly. But, some would say, in the beginning stages, they are peculiar enough to keep around.

Occasionally, the growth above the gall may weaken and either fall off or need to be pruned. The gall is likely inhibiting the movement of nutrients to the end of the stem.

Which Roses Are Most Susceptible?

Close-up of an unopened rose bud affected by Gall wasp (Diplolepis rosae). As a result, several small round growths with a mossy exterior of a green-red color formed on the bud. The rose bud is red.
Hybrids and stressed roses are prone to galls.

There is no clear evidence indicating which roses are more prone to mossy rose gall, but gardeners seem to notice a pattern between bushes that are affected more often.

You will most likely see mossy rose gall affecting common hybrid tea roses or multiflora roses in the United States. Early reports show that Rosa canina was also one rose found to commonly be infected in the U.S. The issue is more common on roses residing in Europe.

Also, there is some evidence to suggest that stressed roses are more likely to be “infected” compared to healthy roses.

How Do You Prevent or Treat Mossy Rose Galls on Roses?

Close-up of Rose bedeguar gall on a rose bush against a blurred green background. Rose bedeguar gall is an intricate and visually striking growth found on wild roses caused by the larvae of the gall wasp Diplolepis rosae. Initially appearing as small, green, or red spherical structures, they mature into large, dense, and multi-chambered galls resembling a mass of tangled fibers or a bristly ball, with a reddish or greenish hue. The gall's surface is covered with fine, hair-like structures, giving it a unique and textured appearance.
Removing galls via pruning is the best method despite limited efficacy.

As mentioned before, the galls are not harmful to the plant, but you’re probably eager to get them out of your garden–especially when they turn ugly grayish brown.

Unfortunately, there is no real cure or prevention. Some people suggest spraying for the wasp, but most sprays are not only ineffective (the wasp can fly away, and you don’t know when they’ve deposited eggs in the plant), but they do more harm than good. 

First, the larvae exist deep within the gall for protection, so sprays will not affect the larvae, and second, the wasps are only around to lay their eggs and move on.

The best way to get rid of galls is to prune them out. Some gardeners report that pruning out the galls will reduce the amount of mature female wasps that hatch in your garden and therefore reduce your chances of galls. This may or may not be true.

Regardless, if you don’t like the look of the galls, prune them out and destroy the affected stems by burning or burying them. You can use these Felco pruners to get the job done. 

Mossy Rose Gall Look-Alike

Close-up of Spiny rose gall on green rose leaves. Spiny rose gall appears as small, densely packed clusters of spiky, needle-like projections on rose leaf. The spines are pink and closely packed together, giving the gall a formidable and prickly appearance.
Spiny rose gall is a similar gall that grows on wild roses.

While you may not think that the spiny rose gall looks exactly like mossy rose gall, you may have run across this look-alike before. Spiny rose gall is also caused by a cynipid wasp, but this one is Diplolepis bicolor, not D. rosae.

Spiny rose gall is round with many pink spines on the surface. Reports show that spiny rose gall is usually exclusive to wild roses. Again, there is no proper treatment for spiny rose gall. It is only an aesthetic issue.

Interesting Historical Facts

Close-up of a mossy rose gall on a blurred green background. The mossy rose gall, scientifically known as Diplolepis rosae, appears as a compact, spongy growth on the stems of rose plants. It is characterized by its irregular spherical shape, and is covered in a dense layer of fine, greenish-pink hairs resembling moss.
Historically, bedeguar galls were used as remedies for various ailments.

Interestingly, humans used “bedeguar galls” to cure many ailments throughout history. The word bedeguar comes originally from Persia and means “wind-brought.” Undoubtedly, early gardeners didn’t understand that the galls came from wasps.

A few hundred years ago, people collected bedeguar galls from affected roses and usually dried and powdered them. A mixture of gall powder and honey supposedly cured baldness. Other historical accounts show people believed in using the mossy galls as treatments for diarrhea, dysentery, worms, and scurvy. The Italians believed for a short time that the powdered galls could cure the bite from a venomous snake!

Mossy rose gall is also called “Robin’s pincushion,” referring to a woodland sprite in English folklore named Robin Goodfellow. This sprite also shows up in Shakespeare’s play A Midsummer Night’s Dream as the character Puck. At early stages of development, the galls resemble a sewing pincushion, and the random nature with which these galls develop likely inspired this name.

Final Thoughts

So, what should you do if mossy rose galls show up on your rose? The wisest thing to do would be to remove the gallsby pruning. This can help in preventing future infestations since most larvae are female wasps, and the pesky female wasps don’t need a male to reproduce! However, mossy rose galls are not harmful to roses overall.

As gardeners, we love to show off the beautiful, exotic, and downright strange things that can happen in our gardens. Some like to keep the galls on to show others and for their own viewing pleasure! Whatever the case, just remember that at one time, people slathered mossy rose gall powder and honey on their heads to reverse baldness. Now, that’s a talking point during any garden tour for sure!

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