Strange Growth in a Tree

— Written By Peg Godwin and last updated by
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October is still several weeks away but high above the ground I found a large witches’ broom. This odd-looking, broom-like growth is nestled in the branches of a tall pine tree. It is a curiosity to behold.

A witch’s broom is the term used for an unusually dense and compact cluster of twigs and foliage. It appeared in the beginning to be a squirrels’ nest. The mass of shoots coming from a central area now looks like a very large green ball in the tall tree. It has lasted for several years growing larger during the many months as the tree continues to mature.

Many plants produce witches’ brooms including:  oak, black locust, hackberry, Buddleja, rose, blackberry, pecan, cherry, Rhododendron, hickory, sycamore, lilac, walnut, willow, dogwood, ash, honeylocust, peach, elm, juniper, firs, hemlocks and pines. There are also a number of factors that cause a plant to respond with a great proliferation of short internodes. The list of known causes includes:  fungi, phytoplasmas, mites, aphids, dwarf mistletoe, viruses, genetic mutations as well as adverse environmental conditions.

Fall seems to be a good time of year to locate these curious growths as foliage color is changing or beginning to drop from plants. Some horticulturists take great interest in witches’ broom genetic material because it may have a totally new makeup. There is an opportunity to develop more diversity in the plant kingdom. The new genetic material can be propagated and may produce unusual characteristics including size, shape, color and texture. Some of the witches’ brooms growing on conifers will produce cones and seed. Propagation of witches’ brooms in conifers has lead to the development of over 40 unique dwarf cultivars.

If you notice dense structures in a plant that look abnormal, take a second look to see if you can spot the witches’ broom. They form in many locations on a tree from the lowest branches up to the very top. Brooms can grow to be quite large or they may be small and well hidden except to the most observant hunter. Some plants contain only one broom while others may have many scattered throughout the tree. If you find the growth unsightly it can be pruned out by cutting several inches below the growth. Witches’ broom does not threaten the life of the plant on which it is growing.