Tree Buds

Trees produce buds for the next year’s leaves, flowers and shoots.  They are small and not easily noticed among the foliage of a fully leafed-out tree, which is why they are easiest to spot in winter.  Buds develop in late summer, when a tree has lots of energy from the sun, but is no longer growing new leaves and branches as the tree prepares for winter.

Tree buds remain dormant through the winter.  In spring, as daylight lengthens and temperatures start to warm, buds will burst open.  Buds contain the beginnings of a leaf, a shoot, or a flower.  Terminal buds, located at the ends of branches, grow into new shoots.  Lateral buds, growing along the sides of branches, produce either vegetative shoots or flowers.

Lateral buds that grow into flowers are well camouflaged and easy to miss.  Frequently, flowers are dark red or green in color and are quite small, easily blending into the foliage.  Many trees are wind pollinated, so there is no need for the flower to be showy.  Once the flowers are pollinated, they quickly die; many only live for a few days.

Terminal buds appear at the ends of branches and will create new shoots, allowing the branches to grow longer.  These buds release a hormone named auxin that slows or prevents the growth of lateral buds on the same branch, so all of the energy for that extension of the tree goes into growing new wood.  Arborists may prune terminal buds before they open to stimulate lateral bud development, thus controlling the shape of a tree.

Many buds are covered with scales.  These are small, modified leaves that protect the bud in winter against cold, freeze damage, and drying.  Buds contain stored energy in the form of sugars and nutrients to be used as soon as the buds burst in spring.  This makes buds attractive as a winter food source for aphids, cedar waxwings, finches, squirrels and deer.  Trees can lose some of their buds, but excessive predation could stunt tree growth.

As you are out walking in the next few weeks, you will be able to see many trees with their buds getting ready to open.  You may want to take along a field guide that describes characteristics of tree buds that can be used in winter tree identification.  Two good ones are Winter Tree Finder by May Theilgaard Watts, and The Tree Identification Book by George W.D. Symonds.  Both describe tree bud shape, color, size, and orientation, in addition to other tree parts.