Weeds

In church today the parable of the mustard seed was read. I've always thought of it in terms of God's power to take something small, like what we can do for Him or offer to His kingdom, and turn it into something large and amazing. Today in church it was interpreted a bit differently. It was pointed out that mustard plants were fast-growing weeds, especially in fields. They would spread and cover an entire field incredibly quickly (dandelions were suggested as the modern equivalent)--so God can work incredibly quickly with the small amount that we can offer him. This, in turn, suggested to me the idea of invasive species. Invasive species often invade fields, because they are bare and easy to grow in, and are unwanted both by the farmer and by society at large. Is God and His word a sort of invasive species here on earth? Unwanted to worldly residents? Something they attempt to eradicate but can never quite manage? Something that isn't native, in some sense doesn't belong? It seemed like a pretty good comparison to me.