What is the first plant that pops into your head when you hear the word weeds? All plants evolved somewhere, so a weed in one location is a native somewhere else. 

For example, the dandelion is native to Eurasia, but not the United States. However, Iowa has the same temperate climate as Eurasia. So, once the plant arrived via bird or someone’s traveling trunk, it survived very well. 

Consider the Iowa prairie natives rock dandelion and false dandelion. They look so similar to the Eurasian dandelion that without help we’d be hard-pressed to identify the weed. 

So, do weeds really look like weeds? The term “weeds” is not a taxonomic classification; i.e. there are no distinguishing traits shared by all plants in the group. So, then why should we care about weeds, and is it important to distinguish them from other plants? 

Ecologically speaking, a weed is a plant that is an opportunist:  its seeds quickly germinate and grow in open spaces, and produce lots of offspring before death. This is especially true in highly disturbed environments; for example a cornfield. Corn grows quickly and produces a lot of offspring (is it a weed?). Another example: dandelions that grow well in lawns do not flourish in prairies because they are poor competitors against native perennials. 

From a farming point of view, a weed is any plant that is growing where it is unwanted because it interferes with crop production. For example, the native butterfly milkweed is unwelcome in the same cornfield previously mentioned. 

Obviously, there is conflict on what constitutes a weed.  Is this really a problem in Iowa? And why should we care? In fact, if crop production is harmed, why should we save native prairie plants?

Iowa has often been termed “the most changed state in the U.S.” because it lost 99.9 percent of its prairie within 100 years. Based on the farming point of view, all of our native prairie plants are weeds, so change is “good.” But is it good from an ecological perspective? Maybe we should consider saving weeds, but which ones is difficult considering that there are well over 180 native species found on small native prairies.

Each of these species contain tens of thousands of years of biological history that once exterminated are gone forever. Many organisms that eat these species or live in roots will also disappear if we lose their plant hosts. 

For example, the native Monarch butterfly can feed on nectar of many different plants, but its larvae must feed on the native milkweed.  If we lose this particular plant species then we lose the monarch. If only this butterfly species becomes extinct we probably won’t lose spiders that eat it, but as each species’ loss adds to the total, then the accumulation leads to potential losses of spiders, etc.