Adding mulch to your garden or landscaping is an easy way to help plants thrive, since it locks in moisture and blocks out weeds. It can also be expensive: about $11 for an 8-gallon bag. Instead, get mulch for free. Your local parks and roads departments regularly haul away dead or fallen trees and grind them into mulch. It's free for the taking. If you’re worried the mulch may come with weed seeds, simply seal it in black garbage bags and let the sun’s rays exterminate the seeds. Spread the mulch, and reuse the bags for garbage. Savings: hundreds of dollars.