Regarding your questions about lawn renovation, I have found a few options for you:

1. If the weed-and-feed product is for pre-emergent weeds, this would not work on your lawn, which already has dandelions growing actively. If the product is post-emergent, it will kill the dandelions, but if you are planning to sow grass seed, you will need to wait before sowing (different products have different guidelines, so check the directions on the package carefully). According to The Lawn Bible (by David R. Mellor, 2003), you should also make sure that the herbicide will target the weeds you have. Do not spray in windy conditions, and only treat areas which need it.

Overuse of herbicide destroys valuable bacteria and insects in the soil, so prevention is the best: mow the lawn high, which will keep weeds from getting established, as they need light to thrive; don't scalp the lawn; water only when it is too difficult to press a screwdriver into the top 2 inches of the soil.

2. There are less toxic alternatives. Some sources say that corn gluten prevents weed seeds from sprouting. They must be wet to be activated. (It won't work on dandelions which are already thriving in your lawn.) There is a product called Organic Weed Stopper Plus Corn Gluten Meal (from Walt's Organic Fertilizer Company in Seattle) which can be used: they recommend March 15 for getting rid of crabgrass, and August 15 for fall dandelions. (Please note that subsequent research suggests corn gluten may be ineffective as a weed control method. See this Oregon State University study.)

According to Ann Lovejoy's book, The Handbook of Northwest Gardening, corn gluten should be spread at a rate of 20 pounds per 1,000 square feet of lawn. Do this two or three times a year (in spring and fall, with a summer booster as needed). For ongoing weed suppression, apply it in small amounts whenever you pull up weeds (make a paste of corn gluten and water).

3. The Lovejoy book also has a recipe for fall lawn renovation:
a. Mow the existing grass as short as possible.
b. Spread 1 inch of clean crushed quarter-ten gravel (not pea gravel) evenly over the entire surface.
c. Spread 1 inch of compost over the gravel.
d. Top-seed with a regionally appropriate blend if the lawn is thin and spotty.
e. Wait 6-7 weeks before mowing again.

A criticism of weed-and-feed products is that they will add excessive amounts of phosphorus to your lawn, which will actually encourage weed growth once the herbicide breaks down.

Seattle Public Utilities has good information about controlling dandelions without using weed-and-feed products.

(See also the 6 Steps of Natural Lawn Care in the left-hand menu.)

And, Washington Toxics Coalition has information on an overall approach to lawn care

Season All Season
Date 2007-12-06
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From what I can gather, it looks like there are two broad types of common weed grasses that come up in lawns. They are annual weed grasses and perennial weed grasses. Each has a different method of control. To find out what kind of unwanted grass you have, please bring a specimen to the Hyde Herbarium at the Center for Urban Horticulture, where someone can identify your grass free of charge.

I have found several print resources that address the problem of weed grass. Unfortunately, I cannot recommend a remedy. I can, however, offer you some general information about weed grasses and remedies. Here are some selections:

For Annual Grasses:
"Most summer annual grasses can be controlled with preemergence or postemergence herbicides. Preemergence herbicides are often effective with only one properly timed application; however, in areas of severe weed pressure two applications placed six to eight weeks apart may be required for satisfactory weed control. Fenoxaprop (Acclaim) often controls summer annual grasses in cool-season turfgrass communities..."
Source: A.J. Turgeon. Turfgrass Management, Fifth Edition. 1999 p. 247.

For Perennial Grasses:
"Most perennial grasses cannot be controlled selectively in cool-season turfgrass communities. Mechanical removal or spot treatment with nonselective herbicides (principally glyphosate or glufosinate) are the only means by which most of these perennial grasses can be removed."
Source: A.J. Turgeon. Turfgrass Management, Fifth Edition. 1999. p. 249.

"The undesirable coarse perennial grasses, such as quackgrass, nimblewill, and bermuda in northern lawns, are so similar to lawn grass in behavior and physiology that no really good means of selective elimination has been developed."
Robert W. Schery. The Lawn Book. 1961 p. 151.

All Grasses:
Lastly, Taylor's Weekend Gardening Guide to Safe and Easy Lawn Care recommends mechanical weeding and then a treatment of topsoil and grass seed. 1997. p. 95.

For specific herbicide recommendations, please consult the King County Cooperative Extension Master Gardener Clinic.

Season All Season
Date 2006-11-02
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Local plant expert Arthur Lee Jacobson has written about crabgrass (Digitaria sanguinalis)in his book, Wild Plants of Greater Seattle (2008): "Crabgrass is difficult to get rid of because it seeds itself at an almost unbelievable rate; mowing simply makes if flower nearer to the ground. Control demands diligent weekly hoeing and pulling by hand, from July through at least September. Even a few specimens left to reseed ensure more seedlings next summer."

According to Ecologically Sound Lawn Care for the Pacific Northwest by David McDonald (Seattle Public Utilities, 1999), weed invasions are best prevented by making a habit of aerating and topdressing to correct soil compaction and build fertile soil. He recommends that you "overseed at summer's end with locally adapted grasses to fill bare areas with grass rather than weeds. Correct acidity or poor drainage. Mow higher (2-2 1/2 inches, or 1 inch on bentgrass), fertilize moderately with slow-release or natural products, water deeply and infrequently in the summer. Tolerate some broadleaf plants like clover and daisies. Hand weed or spot-spray problem weeds in spring or fall to stop them before they spread."

There is additional information on crabgrass from University of California, Davis Integrated Pest Management, excerpted here:
"Because crabgrass spreads and reproduces primarily by seed, any cultural operation that reduces seed production will decrease crabgrass. There are also a number of cultural operations that increase the vigor of turfgrass, thus decreasing the potential for a crabgrass invasion. These include using the proper mowing height for turf, applying fertilizer at the correct time of year, selecting the best turf species for your area, overseeding to keep the turfgrass thick, and properly irrigating turf.
Fertilization can also be used to increase turfgrass vigor and reduce the possibility of a crabgrass invasion. The best time to fertilize is when the turf is actively growing, which depends upon the turf species grown. Because crabgrass is not very competitive, a vigorously growing turf will crowd out crabgrass seedlings.
Selecting a turfgrass that is adapted to your local conditions will also help produce vigorous turf. (...) Irrigation timing and amount can also affect crabgrass germination and growth. Turf that is overwatered or has frequent (daily) light irrigations becomes weak and vulnerable to invasion by this weed. Irrigating infrequently (once a week) will improve turf vigor. Crabgrass is often found first in open areas where there is no turf, along sidewalks where the soil may be warmer, or around sprinkler heads where turf is mowed closer.
In the landscape, crabgrass can easily be controlled with mulching, hoeing, hand-pulling when the plants are young and before they seed, or with solarization.
In shrub beds, bedding plants, or around trees, mulching with wood products (wood chips, nuggets), composted yard waste, or synthetic landscape fabrics covered with a mulch will control the germination and establishment of crabgrass by blocking sunlight needed for its germination and growth. The depth of a mulch depends on the size of the particles: coarse mulch may need to be 3 to 6 inches deep to control all weeds, whereas a finer mulch may need to be only 2 to 3 inches deep.
Clear plastic mulching (solarization) is effective for eradicating crabgrass plants and seed if it is applied during periods of high solar radiation. (...) Before applying the plastic, closely mow the crabgrass, remove the clippings, and water the area well. It is not necessary to cultivate before solarization, but a shallow cultivation may improve control. Place clear, ultraviolet (UV)-protected polyethylene over the area for 4 to 6 weeks. Shade will reduce the effectiveness of solarization because it limits the amount of radiation. Solarization works most effectively when there is no slope in the land or if there is, the slope has a south or southwest exposure. Temperatures are not as high under plastic placed on a north-facing slope; consequently, control is not as effective. After solarization, do not cultivate the area deeper than 3 inches to avoid bringing weed seed into the upper soil layer."

King County has information on best practices for maintaining a healthy lawn.

Washington Toxics Coalition also has a helpful lawn care fact sheet that might be helpful to you.

Since the weed-and-feed approach to the problem was not effective (and chemical weed and feed should be avoided), I recommend trying some of the cultural controls discussed above (mow higher, only fertilize at appropriate times and don't use quick release fertilizer, water less often but more deeply, improve drainage by aerating, build soil by mulching). Solarization might be an option if the problem can't be addressed by hand-weeding combined with the other methods described.

Season All Season
Date 2009-04-02
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