- Author: Chris McDonald
We are all working very hard to get rid of weeds once we see them, but often I forget to ask how that plant got there in the first place.
There are 4 main ways for weeds to appear on your property: germination from the seed bank, the wind, animal dispersal, and movement by people. (Ok, really its 3 since people are animals too, but I've only seen squirrels driving tractors on the Internet and not in real life).
Of these 4 areas I want to talk about the last, movement by people. I think it is the option we have the most control over, and is the least recognized way of moving seeds. We know that marestail, aka horseweed (Conyza canadensis) seeds can blow into our properties. One could also reduce the addition of seeds from the seed bank (by reducing tilling, plowing or altering the depth of those), but how often do we worry about seeds moving into our properties?
I think, one of the simplest things to change would be the inputs from human sources, its also very difficult to change our behavior. Lets take an example, boots (yes the rest of this blog is devoted to footwear, and not even fashionable footwear). In one study scientists asked walkers to walk through a damp soil sample then through a tray of Brassica seeds (100 seeds) and then walk varying distances from 5 m to 5 km (5 yards to 3 mi.). At the end of the walk the footwear was collected and the seeds still attached to the boots were counted. The biggest news is that even after 5 km (3 mi.) seeds were still attached to the footwear! Good news, most seeds fell off after a short walk. Bad news, the walkers were able to pick up seeds on their boots and help them travel very far. Good news, none of the original seeds were found after walking for 8 hours.
This confirms what we all know: our boots are a great way to move seeds around. What is interesting is that so many seeds move so far. I make it a regular habit to clean my boots before I get into my truck at the end of the day or drive to a new site. I know I'm one of the oddballs who regularly clean the seeds off of my boots. I'd love to change that dynamic and have the oddballs not clean their boots.
Imagine this, if you have 10 people (hikers or field workers) who enter your property when the soil is damp and then walk around to work or hike. There are thousands of seeds moving short distances from the source (a few feet), hundreds of seeds moving a little bit (10 yards or less), handfuls of seeds moving 100-500 m (about 1/4 mile or less) and a few seeds moving several miles.
Do you have an adequate plan and techniques to keep new weed seeds from entering your property just from contaminated boots?
Human Mediated Dispersal of Seeds Over Long Distances
Wichman et al. 2009. Proceedings of the Royal Society.
http://rspb.royalsocietypublishing.org/content/276/1656/523.short