weedy isnt necessarily bad. its actually one of the main things i look for in plants when im searching for biomass producing plants. they grow fast and create shelter for more delicate plants. here the cosmos dont spread on their own unless the soil is bare or lightly mulched. that doesnt happen too often around here. so they pretty much stay wherever i plant them. weedy is one thing, invasive is another. do they disrupt the ecosystem or do they just grow too well?