Plants of the Western Slope June 8, 2016

By Evelyn Horn


Jim Hill Mustard

Along this familiar stretch of road there were clumps of Jim Hill Mustard last week. And here they are, still in full bloom! Another name for this common weed is Tower Mustard and it's easy to see why. These plants have grown over the past week and now they're over two feet tall. But I've seen them even taller, like four to five feet! And Jim Hill? He was a railroad magnate and these plants grew readily in the disturbed soil by the railroad tracks. They are weeds but I find them interesting.

First, the yellow flower is big enough to see -- nearly half an inch broad so the six stamens are obvious and that's a major clue to the mustard family. Often plants have the same number of petals and stamens, but not in mustards: four floral petals but six stamens. And with mustards, the seed pods come in two styles: round and flat (called a "silicle) or long and narrow (called a "silique"). On the right side of Al Schneider's photo is a seed pod with a remnant of a faded petal. The pods can be mistaken for branches!

This tall plant comes from a taproot and when you consider how tall it is, it becomes clear that the plant could travel a long distance if it were uprooted. And so it is. When the wind blows, the plant can become a "tumble weed." It can be blown across the countryside and on roads where it tends to bounce along. I think it would fool most folks! So when fall arrives, you might take note of tumble weeds. They come in a variety of forms!

The plant was named by Carlos Linneaus back in 1753. His history is fascinating to me. At that time, descriptions of plants were exactly that -- descriptions, and they were often lengthy. Linneaus set up the system that describes a plant with just two names. The first is the genus (large group name) and the second is for the individual plant. So we have Sisymbrium altissimum with Sisymbrium being an ancient Greek plant name and altissimum meaning "very tall."

The system is still in use and I often think back to Linneaus' time when he described human beings as Homo sapiens. People considered us to be separate from other creatures and we needed a separate designation!