No matter how carefully I plan, no matter how perfect the growing conditions, it’s inevitable that I find gaps in the garden in late summer. Clearly, I’m not alone, or there wouldn’t be such a market for potted mums in September. Thing is, it’s tough to find holes exactly the right size for big potted fillers, and the dense, mounded form of container-grown mums make it hard to have them look loose and comfortable, instead of like blobs dropped into the garden. With a little advance planning, annuals can be a much better-looking option for filling spaces and adding fall color.