What is a Witch’s Broom?

What is a Witch’s Broom?

Now that grafting season is in full swing, we are setting out to collect many of the witch’s brooms we have discovered in the past year. But what is a witch’s broom exactly? It is a mutation on a tree that causes a portion of the branches to grow much slower from a certain point. After a few years, this anomaly is much easier to see since it appears as a dense, often globose, appendage on the tree.

A witch's broom in a tree
A witch’s broom in a tree

Sometimes these are caused by mistletoe, fungi, or insects, but the ones which can be successfully propagated as dwarf trees are caused by genetic mutations. In many cases, it is difficult to tell the difference between the genetically stable brooms and those created by external factors. However, if there is a high concentration of witch’s brooms in a particular area, there is a good possibility that they could be caused from a mistletoe infestation or other pathogen in the area.

Pseudotsuga menziesii 'Mt. Angel Blue'
Pseudotsuga menziesii ‘Mt. Angel Blue’

A couple years ago, our employee Sam Pratt gave a presentation on witch’s brooms at a horticulture class at Chemeketa Community College in Salem, OR. After having heard about the broom hunting he did in his spare time, another student, Stephanie Krieg, set out to find some witch’s brooms as well. A few days later, she was golfing and found two witch’s brooms at the golf course!

pseudotsuga menziesii 'mt. angel blue'
Pseudotsuga menziesii ‘Mt. Angel Blue’

Only a few weeks later, Sam was joining her at the golf course to retrieve these brand new finds which would later be named Picea abies ‘Stephanie’s Green Golf Ball’ and Pseudotsuga menziesii ‘Mt. Angel Blue’. The latter one is a compact Douglas Fir that produces cones, and it is currently available for sale.

abies grandis 'howell prairie'
Abies grandis ‘Howell Prairie’

Recently, we retrieved a witch’s broom from a tree less than 10 minutes from the nursery! Sam Pratt and Doug Wilson discovered this one early in the fall, and after receiving permission from the property owner to take some cuttings, we had the ability to propagate a brand new variety of Abies grandis which was named ‘Howell Prairie’ for the nearby community.

If you happen to spot one of these fascinating growths in a conifer, feel free to send us a photo or even share some cuttings, and we will custom propagate it under a name of your choosing! Broom-hunting is a fun weekend activity—like a conifer treasure hunt!
The propagation process is actually pretty simple. To see a short, informative illustration, see the video below.

In addition to grafting the witch’s broom itself to obtain a unique dwarf, many witch’s brooms produce cones with viable seed that give rise to dwarf seedlings. These witch’s broom seedlings often have superior form to their parent brooms and are more stable and consistently dwarf.
Happy Brooming!

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