"Spray your weeds with diluted vinegar...not only will it kill them, but the plants and soil love it. Read how here, and see the before and after pictures. I just learned about this in my winter gardening class the other day and the teacher has done it for years."
Oh this is exactly what I had in mind with using Thinglink and individual student portfolios!!!! Look a class pic with each student linked to their project. (Projects range from GoAnimate to Flipsnacks to iMovie Trailers.)