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Why are some plants weeds and others not?

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Our Evergreen World

By Sylvia Brockner

We hear a lot about noxious weeds these days, which makes me wonder why some plants are called weeds, and others are not. Just what is a weed?

According to authors of various weed books, the simplest definition of a weed is any plant that is growing where people don’t want it. A bit more finely defined by the authors of “Weeds of the West,” they are “a plant that interferes with management objectives for a given area of land at a given point in time.”
Obviously, the undesirable character of these plants is the most important feature. However, that seems a bit ambiguous for that would mean that a petunia growing and blooming in a cornfield would be a weed; so too would a portulaca growing in the crack between two sections of a paved parking lot. Both of these are desirous popular plants that have made the big mistake of growing in a given area where people do not desire them.
Many of our common weeds are plants that produce sturdy stalks that stand well above the snow to provide seeds for winter birds such as the many species of juncos and sparrows. Also, many of these plants, such as the dandelion, which is now considered a noxious weed because it is a non-native, came to this country from Europe and have spread across the entire nation in a surprisingly short time.
Who decides upon this terminology? I do not know, but it has given the word “noxious” a new meaning of non-native. Formerly, noxious meant “harmful to health or physical well-being.” So, to all who have eaten dandelion greens for years, it is a bit confusing and alarming to see them now referred to as noxious weeds.
Some of the common weeds I regularly see in the foothills are the tall evening primrose, teasle, common burdock, giant ragweed, lamb’s quarters, red-stemmed pigweed, giant mullein, toadflax and curly dock. These are all fairly tall and stand well above the winter snow, but there are many others that are shorter and will soon be covered with snowflakes.
Those that stand tall all winter above the snow are an important source of food for birds as well as lesser mammals such as mice. The tracks in the snow below these stalks often betray the presence of some of the dining animals.
There is no better time to go for a walk than November, especially on Thanksgiving morning, so you can work up a good appetite for dinner. Some days in November are really quite warm, and it is a good chance to study all the various seed containers that nature has provided on all the plants you have seen all summer.
One of my favorite seed clusters are those of the common burdock. The seeds are contained in a large cluster of round fruits that have prickly hook-like thorns, which catch in animal fur or anything passing by to pull the ripened fruit from the cluster and deposit the seeds somewhere else.
In fact, a man who studied this method of seed dispersal invented Velcro. Occasionally, these hooks work too well, and some small birds gets so tangled that they cannot escape and are so securely caught that they perish on the seed head.
When I was a child, I used to pull the round balls of seeds apart and rearranged them to make teddy bears, gingerbread families and all sorts of things for I had a fertile imagination, and like Velcro, these fruits stick well to each other.
Many of these weeds are more common in other parts of the country. I believe this is because they like or need a bit more moisture than they can obtain on our dry hillsides. Most of the ones I see locally are either in a roadside ditch or in a creek-side valley where it is a bit damper.