Invasive weed management

(Question)

I live in the Danforth area and I have a problem with a certain type of weed taking over my backyard every year. I think the weed is from the Bidens family (by the leaf shape and seed).  Unfortunately it’s a very aggressive and almost impossible to manage.  The backyard is sunny and I think the soil is mixed load-clay.
I’m thinking of putting a layer of filter fabric all over the backyard and just cover it with gravel.  I was wondering if you have any other suggestions?

(Answer)

This invasive weed may be of the bidens family, but to help determine exactly what it is, it would be helpful to know if the seeds seen last year were 2, 3 or 4 pronged.

Regardless of this however, if it is a plant you would like to eradicate then mowing, pulling, raking and then covering with polypropelene (dark plastic that blocks out water and light) will certainly help.  It is vital that the plastic is well weighted down with rocks, bricks or other heavy objects so as to maintain a very dark dry environment underneath.  This treatment needs to be left firmly in place for one full year before anything else can be done.

It is interesting to note that the Danforth area is often sandy soiled, not clay, so if the soil was introduced, then likely the seeds came along with it.