What is a Bud Scale?

Mary McMahon
Mary McMahon

A bud scale is a structure found on some plants which protects buds while they are in dormancy or while they are forming. Plants which form buds without scales are said to have “naked” buds, reflecting the fact that the buds are not protected. When buds break dormancy or open up, the bud scales drop away or enlarge and droop to the side, allowing the bud to emerge fully. Bud scales which drop leave behind distinctive markings known as bud scars.

Bud scales can provide overwintering protection to buds.
Bud scales can provide overwintering protection to buds.

Bud scales are modified leaves. They may be hairy or sticky, depending on the species of plant. A common location for a bud scale is on a terminal bud, the bud at the end of a branch which controls dormancy for other buds on the same branch. Using bud scars, people can sometimes determine how old a given branch is, as the number of scars will indicate how many times the terminal bud has broken dormancy.

When buds open up, the bud scales drop away or enlarge and droop to the side, which allows the bud and flower to emerge fully.
When buds open up, the bud scales drop away or enlarge and droop to the side, which allows the bud and flower to emerge fully.

It can be important to determine whether or not a plant has bud scales when using a plant identification key, as scales can be used as an identifying feature to distinguish between different types of plants. Identifying bud scales can also be important when examining plants to see how well they are weathering over the winter, and in identifying early signs of disease. One problem with the protection provided by a bud scale is that it also provides an ideal shelter for fungi, which may overwinter in the bud and then emerge in the spring, infecting the rest of the plant.

When handling plants which use bud scales to provide overwintering protection to buds, it is important to avoid disturbing the bud scales. Knocking a scale off or pinching it may interfere with the health of the underlying bud, which could cause problems for the plant in the following spring. Conversely, pruning and manipulation of buds can be done during the dormant winter months by experienced gardeners to control plant growth to achieve a desired objective.

People may also use the term “bud scale” in reference to spruce bud scale disease, a type of parasitic infection which can be very damaging to trees. The disease is characterized by the appearance of small scales on the tree which house insects and their eggs. Insects can overwinter, emerging in the spring to cause considerable damage, and trees with bud scale disease are vulnerable to fungal infection.

Bud scales protect buds while they are forming.
Bud scales protect buds while they are forming.
Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments

kylee07drg

I have a beautiful flowering tree in my front yard that blooms in early spring. I have heard it called by several names, like the tulip tree, the lily magnolia tree, and the Japanese magnolia tree. I have noticed the bud scales on its blooms.

Two big scales face each other and wrap around to meet at the edges. These scales form what looks like a green baby tulip. As the bloom matures, they separate to reveal a beautiful pinkish-purple flower. When the flower is fully open, the bud scales take a backseat.

These blooms really do look like tulips. It is strange yet lovely to see an entire tree holding up short tulip blooms encased by bud scales with no stems.

Perdido

@Oceana - I like to leave the bud scales on my rose bushes, even after the blooms have faded. Many people cut them off to encourage more flowers to grow, but I like to watch rose hips form underneath the scales.

The scales themselves will turn gray and wither. Attached to their undersides are the little green bulbs that will become rose hips in the winter. These are the seed pods of roses.

When the bud scales are still attached, they make the green hips look like they have a head of gray hair. They eventually dry up completely and fall off, leaving the fruit bald.

Oceana

When I think of bud scales, the first plant that comes to mind is the rose bush. When the bud forms, at first the bloom is fully enclosed by the green bud scales. As the bud gets bigger, it slowly pushes the scales aside until it erupts into a full grown rose. Then, the scales lay out horizontally and cup the bloom.

I like cutting roses with long stems and bringing them indoors in a vase. The bud scales add a touch of green to the blooms, and though they have already served their purpose of protecting the bud, they hang around for awhile.

anon128779

Thanks. You have a great site. Got my answer in seconds.

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