A bract is a part of a plant that may resemble a leaf or a petal. Structurally, a bract is most similar to a leaf, but it usually is slightly different from the plant's leaves. Some bracts are green while others are colored. Colored bracts can be quite brightly colored and are often mistaken for petals.
Bracts can be many shapes, sizes, and textures. They can be larger or smaller than the leaves and petals, and they are generally tougher. Their main function is to protect the flower from pests and harsh weather. When a flower first blooms, it is surrounded by the thick, green bracts. Some plants have two bracts while others have several. The flower blooms and grows out of the bracts, which remain on the plant and form the base of the flower.
A common bracted plant is the poinsettia. On plants like poinsettia and bougainvillea, the bracts are often referred to as “false flowers” because the plant's true flowers are so tiny and hard to see. Bracts that surround flowers in a cluster are called involucre. Poinsettia flowers are small and light green, and the grow at the center of the red involucre. Bougainvillea flowers are white, and about the size of a lentil.
Brightly colored bracts serve to both protect the flower and attract pollinating insects. Other common plants with colorful bracts and insignificant flowers include the dogwood, the vase plant, and the lollipop plant.
On flowers such as daisies and sunflowers, the bracts are the green part that holds the flower to the stem. Bracts of this type are called phyllaries. On grasses and grains, there are two types of bract. These types of plants grow with long clusters of flowers, called florets, at the top. Each floret eventually contains a seed. The flowers are surrounded by two thin, scaly bracts, with an inner bract called the palea and an outer bract called the lemma. The whole floret is surrounded by green leaf-like or spiky bracts called glumes.
Some bracts are adapted to very specific functions. The bracts of the passion flower are coated with a sticky, acidic substance that traps insects. The acid then breaks down and digests the insects to provide nutrients for the flower. On the Lobelia telekii, a tall, conical, furry-looking plant native to cold alpine regions of Africa, the blue-green fur is made up of bracts that act as insulators.