Sunday, January 27, 2013

Hackberry Witches' Broom


Looking up into a Hackberry Tree (Celtis occidentalis) you might notice a branch with an unusually dense cluster of twigs.  These are known as Witches' Brooms.    Their exact cause is unknown, perhaps some injury or stress to the tree.  Associated with the Witches' Broom formations are two organisms, an Eriophyid Mite, Eriophyes celtis and a Powdery Mildew, Podosphaera phytoptophila.

Enlarge picture for more detail
I think a post on Eriophyid Miites is in order some time in the near future.  They are both ubiquitous and virtually unknown to the casual observer. 



Saturday, January 12, 2013

Little Brown Mushrooms in January

It's not too often that one finds mushrooms growing in January, and I'm not sure why I noticed these because they are incredibly small.  We've had some unusual warm, rainy weather which I imagine is what allowed this fungi to fruit in January.

I think they are Bark Mycenas, Mycena corticiola.  They growing on mature White Pines.  M. corticola  doesn't have a preference White Pines, but rather mature trees with a well developed bark layer.
Like some species of Marasmius, M. corticola will dry up and seemingly disappear, but revive when exposed to moisture.  I suppose this feature is what allowed these mushrooms to appear so quickly in January.  The weather has already turned more seasonable cold, it'll be interesting to revisit the same trees in a few days to see what has happened to these mushrooms.

Early Morning Window Frost

Frost forms on windows when cold air outside cools down warm, moist indoor air.  The patterns are the caused by dirt, grease, imperfections, or other residues on the glass.  If you have a clean window, there will be less patterning.  Hurray for dirty windows!

We have an old house with some old windows.  Because they are less efficient, there's more "contact" with the outside air, and more likely to form frost than newer windows.

I like this Guide to Frost at Snowcrystals.com


Thursday, January 10, 2013

Stinging Nettle Look Alikes

 Please note that this post is most relevant to central MN.  I imagine it could be useful to those living elsewhere in North America, but there are likely to be other look alikes. 

This past summer, I was asked about the difference between Stinging Nettle and Wood Nettle, good plants to be familiar with since both can cause a painful rash when touched.  While pointing out the differences, a couple of other look a likes were discussed, Clearweed and White Snakeroot.  Overall, they resemble one another; each shares a similar pointed oval leaf shape with toothed edges, and can be found in the same area (though habit preferences for each aren't necessarily the same).  First, let's introduce the plants in question.

Stinging Nettle - Urtica dioica ssp. gracilis

Wood Nettle - Laportea canadensis

Clearweed - Pilea pumila

White Snakeroot - Eupatorium rugosum


Next, some comparisons of the four plants.  By the way, I'm keeping my terminology purposefully non-technical.  Some details might be missed, but I want to make the information accessible as possible; I imagine there are a lot of people who would like to be able to recognize Stinging Nettle.


Flowers:  Are they growing at the top of the plant, or along the sides of the stems.  Wood Nettle and White Snakeroot have flowers at the top of the plant, Stinging Nettle and Clearweed have flowers along the sides.  You could argue that White Snakeroot doesn't belong in this discussion because its flowers are clearly different (they actually look like flowers).  But before the flowers have fully opened, White Snakeroot looks pretty "nettlish".
From left to right: Wood Nettle, Stinging Nettle, White Snakeroot, Clearweed

Wood Nettle Flowers

Stinging Nettle Flowers
White Snakeroot Flowers
Clearweed Flowers
Hairs on stem:  Are there hairs on the stems or not.  Stinging Nettle and Wood Nettle have hairs on their stem, and on their leaves; it's what causes the "sting".  Clearweed and White Snakeroot do not have hairs on their stems.  Clearweed has a very translucent appearing stem.
From left to right:  Wood Nettle, Stinging Nettle, White Snakeroot, Clearweed

Leaves:  Are the leaves arranged opposite along the stem, or alternate?  Wood Nettle is the only one that has alternate leaves.
From left to right (two leaves of each): Wood Nettle, Stinging Nettle, White Snakeroot, Clearweed
Below is a table summarizing the above information: