Brooms in the canopy

 And here's another sign from the Dalrymple Creek trail:

This one I had to clean up a bit to be able to see the mistletoe photo.

Sign text: Tree Parasites. Mistletoe, Witches Broom. Weyerhaeuser. 14.

Weyerhaeuser is the wood products company that left this patch of forest uncut, and provided the signage and pamphlets. 14 probably refers to the section in the now lost pamphlets.

I looked for the mistletoe in the trees near the sign, but didn't find any, possibly because it is near the tops of the trees, too far away to see without aid. Or loggers boots.

But 'way up there, there were clusters of witches' broom.

Witches broom in the canopy.

Mistletoe causes the tree to grow fat branches; there may be a few in this photo.

The sign is wrong: mistletoe is a parasite. Witches' broom is not. Mistletoe is a plant that grows on the tree, mostly underneath the bark, taking nutrients and water from the tree. The shoots that bud out of the branches produce the seeds and expel them away from the host tree.

Witches' broom is part of the tree itself, a response to stress, in this case the challenge of the mistletoe, but it could also originate with other stressors.

A view of Dalrymple Creek. Notice the tangles of witches' broom at upper right.

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Un letrero en el bosque nos advierta de la presencia de parásitos de los árboles.

Dice el letrero: Parásitos de árboles. Muérdago. Escoba de brujas. Weyerhaeuser. 14.

Weyerhaeuser es la compañia maderera que nos dejó los anuncios y los folletos (que ya no existen). 14 sería el número de la sección en el folleto que explica el letrero.

El letrero se equivoca. Muérdago es un parásito; la escoba de brujas, no.

El muérdago es una planta que crece a base del árbol; la mayor parte de la planta se esconde bajo la corteza. Allí toma los elementos nutritivos y el agua que necesita directamente del árbol. Los brotes que salen al aire producen sus semillas y las lanzan fuera del ámbito del árbol invadido.

Busqué alrededor del letrero para ver si podría hallar el muérdago, pero no lo vi. Creo que estaba allá lejos, arriba en la fronda.

La llamada "escoba de bruja" no es un parásito, sino la respuesta del árbol a un estrés, en este caso, el muérdago, pero podría ser, en otros sitios, algún otro problema, sea hongos, insectos, y otros organismos.

En las fotos se puede ver el lío de ramas que constituye la escoba de brujas.

Not a pretty picture

I didn't know this.

Hoomak Lake sign: Dwarf mistletoe

Legend: Dwarf mistletoe are perennial flowering parasitic plants. They live on and injure their host, in this case coniferous trees. In BC., dwarf mistletoes can cause extensive damage in our forests, resulting in the loss of valuable wood. On the coast western hemlock and mountain hemlock are the principal tree species affectd. Some forests containing large volumes of hemlock are seriously damaged.
Notice masses of thickened branches in the trees in front of you. They are called "witches brooms", and are the result of dwarf mistletoe in western hemlock trees. The mistletoe parasite will eventually kill the host tree.

This was written 20 years ago. The poor tree in front of me as I read the sign is long dead.

Legend, continued: The dwarf mistletoe plant looks like a leafless, segmented, woody stem. It is a greenish-yellow colour and it "roots" in the host tree, absorbing nutrients from its host. It grows in a small mass of shoots just a few centimetres long. New plants are formed when a single sticky seed is projected from an exploding mature fruit and lands on live tree bark. Removing the infected trees is the optimal way of eliminating dwarf mistletoe.

And here's that infected tree.

Not a pretty picture.

I have seen trees like this before, and wondered briefly what chewed them up, out here in the forest where no machinery wanders. I never looked too closely; just shuddered and went on my way. Now, I paid more attention, and came home to study up on it.

Look at the photo above: you can see the short stalks of the mistletoe. They sprout directly from the tree bark, and almost, but not quite look like part of the tree. Also note the fat branches. The root system interferes with the normal growth of the branches. These thick branches are weakened, and easily broken (in a wind storm, for example).

Fat branch and "brooms".

The balls of deformed branches plus a tangle of mistletoe are called brooms. (Not my idea of a witches' broom, which is designed for speed. Not these.) They don't appear until the tree has been infected for several years; at first, the mistletoe lies hidden beneath the bark.

The mistletoe damages the tree in other ways; it absorbes its nutrients, primarily carbohydrates, from the tree sap. And it can somehow extract water from the tree xylem even in times of extreme drought. The tree above the mistletoe infestation is starved and thirsty, and dies off.

I have looked at these and said "How ugly!" I have thought they spoiled the forest. I cringed at the sight.

I was wrong. I've been too stuck on my limited human ideas of beauty. These witches' brooms are valuable wildlife habitat. My "Wildlife and Trees" guide mentions fishers, martens, flying squirrels, black-backed woodpeckers, marbled murrelets (endangered), and spotted owls (ditto) as species which roost or nest in the shelter of these knots.

Dwarf mistletoes may contribute in various ways to biodiversity - by creating openings in the forest following tree death, by providing nesting sites in the 'brooms' and by providing food for a range of vertebrates and invertebrates. There can therefore be some conflict between the requirements of forest exploitation, and environmental concerns. (Plantwise Knowledge Bank)

E-Flora BC has several good photos of dwarf mistletoe on live hemlock. Here's one. Next time I see one of these trees, I'll stop and examine it closely, to get a good look at the mistletoe.