Mistletoe in a juniper tree

Continuing to wander through the park led me past this tree:
How odd! It looks like it has two different colors of foliage. And the darker foliage seems to form very distinct clumps.  That’s weird enough to warrant a second glance.  A second glance reveals that those dark clumps aren’t part of this poor juniper tree – they’re mistletoe!

Mistletoe in a juniper

Mistletoe, probably Phoradendron juniperinum, in a juniper tree

The mistletoe growing in this juniper isn’t the mistletoe traditionally associated with Christmas, Viscum album. But like Viscum album, Phoradendron juniperinum is a hemiparasite in the sandalwood family. Hemiparasites aren’t totally dependent on their hosts; while these mistletoes get water and nutrients from their hosts, they can make their own sugars.  I identified this mistletoe as P. juniperinum because it’s the only mistletoe I could find associated with junipers in the western US. If you know of a more likely mistletoe, let me know.

Now that I’ve got a tentative id for the mistletoe, it’s time to pin down what kind of juniper we’re looking at!

I’ve already identified a juniper along this walk.  The giveaway for that juniper was the bark – there’s no mistaking an alligator juniper! The bark on this juniper (visible in the background of the mistletoe picture) doesn’t look a bit like alligator hide.  It’s gray and fibrous instead.  So we can knock alligator juniper off our list of possibilities.  There are only three other kinds of juniper found in this area,

Could it be a Rocky Mountain juniper? Nope! As you can see in the first picture in this post, our juniper is a shrubby little tree with lots of stems.  Rocky Mountain junipers are rarely multistemmed.  Plus Rocky Mountain junipers have brown bark that breaks off in plates.  Our juniper has grey, fibrous bark that shreds.

That leaves Utah juniper and one-seed juniper.  Unfortunately, these can be tricky to distinguish. If I’d noticed juniper berries on our tree, this would be a snap because Utah and one-seed juniper have different colored berries and a different number of seeds in each berry.  (Bet you can’t guess how many one-seed juniper has!) Unfortunately, all I noticed were the male strobili – where pollen is made.  The male strobili aren’t mentioned in the Flora of North America descriptions for these species, most likely because they aren’t very helpful for identification. Even the phenology isn’t particularly helpful here: Utah juniper releases its pollen in early spring and one-seed juniper in late winter.

immature male strobili

Immature male strobili

Despite the lack of berries, I’m pretty certain that this is a one-seed juniper because it’s got several main stems that branch at the base. Utah junipers tend to have short main stems with a rounded or conical crown.  The absence of juniper berries on our tree is another piece of evidence supporting a one-seed juniper identification: one-seed junipers are usually dioecious, whereas Utah junipers are almost always monoecious.

BOTANY-SPEAK TANGENT: The root -oecious means ‘household.’ So dioecious species comprise individuals with only male reproductive parts or only female reproductive plants while monoecious species comprise individuals with both male and female reproductive parts.  (If we used botany-speak for animals, (most) people would be dioecious and worms would be monoecious.)

So, lets call this Juniperus monosperma. I’ll be sure to keep an eye on it – if I find berries, I can make a more conclusive id.