The best pre-emergent that I have used is Snapshot. It is expensive here but worth the price. I have found that it seems to last more than one year. I just need to put it out in the fall to prevent the winter/spring weeds. I am tired of being outside in the late summer (August) when it is so hot and most all the flowers are looking ratty, so I am not motivated to be outside then. One note about Snapshot that Michele mentioned is that you need to be finished digging in a bed where you use Snapshot, because it forms a crust on top of the soil that keeps the seeds from germinating. If you dig in that bed after applying the Snapshot, the weed seeds will come through where you have dug. I have also heard that pre-emergents stunt the growth of daylilies or other plants, but I have not found that to be the case here.
We keep the daylily beds mulched and that keeps the weeds there to a bare minimum. I always try to pull any weeds there when I see them to prevent them from going to seed.
The best preventive measure that we all can take is to get rid of the weeds before they have a chance to go to seed. This is easier said than done. I hand pull weeds and use Roundup in nondaylily areas. We mulch our pathways with free wood chips that a tree service brings us. We have a cow pasture that borders the back of our property. We will always have weed seeds that find their way through the fence and germinate. As a matter of fact, that is where we have the worst weed problem plus in our vegetable garden. (This is where applying a pre-emergent in August would prevent our biggest weed problem.) I would rather have that cow pasture and its weeds any day instead of houses. I plan to pull more weeds this afternoon that are near the cow pasture. The soil is soft now, and the weeds come right up when pulled. Weed pulling is good mental therapy.
