2.3 “Ideal” Weed Characteristics

If we think of global agriculture, there are approximately 250,000 different plant species on earth. Of those, about 8,000 would be what we would classify as a “weed”, something that we do not want growing in our production areas.  Fortunately only 200 to 250 of 8,000 weed species are the ones that are really creating problems for us. While 200 species of the 8,000 is only a small percentage of identified weed species, these 200 can still create havoc for us.

Let’s now think about our field ecosystem from the perspective of a weed population. What types of characteristics would a weed population need in order to be successful in growing year after year? From the “ideal” weed perspective what would be more important for it to have – top yield or would it be better for it to think about more long term survival? It is a bit different from our perspective with crops, where our goal is to have them produce high yield, but not necessarily to survive for several years, unless we are thinking of a perennial forage crop. For crops like corn, soybean and wheat, the goal is to produce a lot of seeds in a single growing season. However, from a weed perspective, the goal is to sustain a successful population long term. With that goal in mind, think about what types of characteristics would be ideal for a successful weed. A few traits that help weeds survive long term are listed below:

• Ability to adapt to a changing environment.
• High levels of genetic diversity among the population.
• Poisonous to predators.
• Not all seeds germinate each year, in case it is unfavorable weather that season. Seeds able to stay dormant in the soil.
• Seeds germinate over a longer period of time, rather than all on one day.
• Ability to grow quickly.
• Produce a lot of seeds and the seeds can be dispersed over a larger area.
• Able to reproduce vegetatively.
• Can compete with other plants for resources.
• Ability to occupy sites disturbed by humans.