Witch’s Broom

Tom Castronovo and the Gardener News will be hosting a symposium this April introducing their garden writers to the public. This event will cover a wide range of gardening topics, helping to educate those interested in the green industry. My topic of discussion will focus on “Smaller Plants for Smaller Spaces.” With residential property sizes shrinking in New Jersey, an emphasis on choosing smaller plants for smaller landscapes will be discussed. And while the topic implies small, there is in fact much to talk about. So much in fact that the topic of where some new plants come from will only briefly be discussed. This article however, affords me the opportunity to go in depth about one way plants are found and produced. So what is a Witch’s Broom anyway?

A witch’s broom is a mutation form occurring on an existing plant. Plant Geeks of the world, me included, hope to find these adaptations of plant life and develop new plants or cultivars from their find. This abnormality is a disease or deformity on a woody plant where the natural occurrences of the plant change. The result is a dense mass of shoots growing out from a single point resembling a broom or a bird’s nest. These congested growths are popularly found on spruce and pine, but are not limited to, as they can also be found on deciduous trees such as hackberry and maple. There are a number of “stresses” which can cause a witch’s broom. Both biological and environmental factors can contribute to the congested masses. Organisms such as fungi, phytoplasmas (bacterial-like organisms), mites, aphids, mistletoe and viruses are to blame biologically.

Factors such as poor pruning practices or other physical damage to a tree may contribute to such an abnormality. Environmental stresses injure the growing points of branches, thus contributing to the formation of a broom. The cause of a broom can be difficult to determine, especially if the cause was an environmental factor. There may be only one broom on a tree or several. The abnormal growths create great opportunities for diversifying the plant world. Often diminutive forms of spruce and pine have been created that fit well into smaller landscapes. However, far too often are similar cultivars being raised, contributing to the confusion of similar, if not exact, plants.

There are innumerable witch’s brooms and the vocabulary of naming them is just as exciting. In 1904 a witch’s broom on a Norway spruce (Picea abies) was found and named ‘Nidiformis’. This well known dwarf Birds Nest Spruce type has a flat top and is wider than it is tall. Horizontal layers of branches with short green needles afford this candidate many landscape possibilities. In 1958 a witch’s broom was found on a witch’s broom in Holland. Picea abies ‘Nidiformis’ provided the world with Picea abies ‘Little Gem’. Little Gem has the tiniest of green needles and has been described as a “living rock”. Suitable in almost any garden, this dwarf conifer could be your next container garden candidate. Another mentionable favorite is Picea abies ‘Lanham’s Beehive’. Founded by Gary Lanham on a mature Norway Spruce, this one has a beehive form. The needles are longer and thicker than most other nest types. They (the needles) also have a slight glaucous tint (a waxy bloom or whitish material that rubs off) and the stems and buds are cinnamon colored. We’re really going deep now! ‘Picea glauca ‘Humpty Dumpty’ is a dwarf White Spruce whose origin is from the popular dwarf Alberta Spruce. This squatty form is as wide at the base as it is tall. The list goes on and on and the vocabulary just gets more interesting. “Thumbelina’ and ‘Witches’ Brood’ are two forms of dwarf Norway Spruce. “Tom Thumb’ is a bright gold, oriental spruce miniature with short, layered branches. This yellow form, and most others, likes a harmonious balance between sun and shade. While most green forms are happiest in sun.

The term witch’s broom comes from the German word Hexenbesen, meaning to bewitch (hex) a bundle of twigs (besom). The next time you go hiking, look around your surroundings up in the trees. You may be able to name your own plant and become immortalized in the plant world. Gardeners interested can obtain more information about witch’s brooms by visiting wbgardens.com. The website features Jan Salma who is a dwarf conifer collector from the Czech Republic. While the site is not the easiest to navigate, it does provide great photographs. Enjoy and happy hunting.