Yeah Bill, Manuel's a part of it...
Well-sited, happy plants another essential ingredient...
Minimized soil disturbance...good mulch...
and yeah, a pre-emergent like corn gluten meal, a by-product of the corn milling industry that produces an enzyme that inhibits root-cell division as it decomposes, thus preventing a high-percentage of germinated weed-seeds from establishing, can be another useful tool. Also provides nitrogen, causing a nice Spring "green-up" on lawns, and lush vegetative growth in perennials.
One caveat, when covered with mulch, corn-gluten decomposes anaerobically, producing a odor to best the most putrid roadkill...yummy!
