bud_wi - Waiting period depends on which pre-emergent you use; commercial ones will have the info on the label; just remember that no chemical knows the difference between a sprout you want and a sprout that you don't want. A lot of time variance is caused by climate - days of rain or heavy irrigation can shorten the length of time the preemergent is effect, vice versa, a long dry spell can extend the time. For CGM, the recommended wait period (before seeding) is usually 4 to 6 weeks - that's the period the gluten is effective. I use whole cornmeal only on already sprouted lawns, but from DH's experiences I would guess it has the timeframe as commercial CGM. One either waits until the seeds sprout before using the preemergent, or waits until the chemically effective period is past. The point of the pre-emergent is to prevent seeds from sprouting, irregardless of whether you want that seed to sprout or not. And re weeds in the garden, I'd recommend using any organic mulch -which would give you both a superb weed-barrier and *improve* the soil; all without worries about what chemical pollution may be doing to the environment. A variation of lasagna-gardening works marvelously to keep the areas weed-free: put down 10 to 20 overlapping sheets (or up to 1/4") of sopping wet newspaper and cover all visible paper with 2" shredded leaves or 5-6" straw or hay or 2-4" mown grass or whatever is handy that will decompose. The paper smothers the weeds; the mulch prevents the paper from wicking moisture - and looks nicer; and the worms will be thrilled and they leave castings which your plants will adore. I mulch all paths heavily, leaving rows or beds open until the seedlings are about 4" tall, when I then tuck mulch around each plant. Tomatoes and peppers get the path lasagna to within an inch of the stem; carrots, lettuce and similar bedders get dry shredded leaves sprinkled over them weekly (I just run my hand across the plant tops to uncover them and brush the dry leaves to the soil). Beans seem to be very fond of lasagna so I plant them in high-hilled rows and make an on-going lasagna with paper and mowings in the paths between rows. And I rarely have a weedling to pull.

I learned a very valuable lesson with my vinca project - we ended up killing (or so I thought) everything on the slope with Roundup, waited a couple of weeks to make sure nothing green came back, then planted the vinca and mulched lightly. The vinca has done very well, but unfortunately crabgrass has engulfed the entire slope. The vinca is doing just fine underneath, but pulling out the crabgrass is an enormous hassle. I have reclaimed about 3/4 of the slope bit by bit but I have now given up and am just waiting for a frost to kill off the rest of the crabgrass. I will have to put down Preen in the spring for sure. I absolutely should have put down a layer of newspaper/cardboard in addition to the mulch. Furthermore, the Roundup application didn't kill deeply rooted things like docks and dandelions, so I have been pulling those out by hand, along with a few other pesky things like clover. I have a feeling this slope is going to be a huge weeding nightmare for at least another year, but the vinca is filling in much faster than I expected, so we shall see.

I whole-heartedly recommend using Preen. A very small amount is effective and often you don't even need to reapply it! My lot is 80% garden and 20% lawn. I use no chemicals other then Preen, totally organic-- even the lawn food-- but I just had to make the exception for Preen. Yes, there are quite a number of perennials which reseed themselves, and as you observe your garden you'll figure out which ones these are. Foxgloves, hellebores, violets, Johnny Jump Up, melampodium (little yellow daisies), blanket flower (gaillardia), orange butterfly weed, and some coneflowers come to mind. So you sure asked the right question! You can just skip the areas immediately around these so they can reseed. That still leaves areas around the shrubs, azaleas, roses, ferns and other perennials; only treat the areas where there's a problem. I find edges of beds are the most important area to treat. Any area of the bed that borders on the lawn can easily be invaded if you have an organic lawn with lots of little "wildflowers" (e.g., weeds!). I rake back the mulch around those edges, apply Preen to the bare soil, water it in and replace the mulch. I could not garden at my age (70) without Preen. It saves so much time at home that I have time to maintain a huge organic rose garden at the zoo, PLUS two smaller rose gardens --one antique and one modern-- at the arboretum. Corn gluten is great for small patches of lawn or the vegetable garden where you don't want any chemicals but it does not remain effective very long. You really need 50# of the stuff; it is a component of livestock feed so you have to go to a feed store to get it. A side benefit of corn gluten is that it has a high nitrogen content and so it feeds the plants. I used it on my organic lawn back in Texas and it worked great. (It would work here too I just can't lift the bags anymore!) Bless you Babs for bringing up cardboard; that would work equally well with edges and the mulch will hide it. Lasts longer than newspaper and breaks down completely except for the scotch tape. I like to use cardboard under paths and between rows in the vegetable garden.

From the Preen website: "How long do I have to wait to seed my lawn after applying Preen Lawn STEPSAVER Weed Control Plus Fertilizer? Wait 10 weeks before seeding, overseeding, or sprigging the treated area." This applies to their special product (as noted) but also applies to their basic weed preventative product. Joe