Everyone agrees that fall is the best time to start, repair or fertilize cool-season lawns. (That means fescues and Kentucky Bluegrass. Warm-season grasses like Zoysia are very different and a topic for a separate guide). Make that early fall: September to October. These videos will show you what to do and how.
General Fall Care Videos

“FALL LAWN CARE“ by Boston-area horticulturist Dave Epstein explains when to feed and when to plant new grass.
“FALL LAWN CARE“ from GardenTime TV in Portland, Oregon covers starting new lawn and feeding existing ones, and makes the case well that both are best done in fall.
“FALL LAWN CARE” by Charlie Nardozzi for the National Gardening Association covers the best time to patch and feed an existing lawn, and how to start a new one. Also recommends top-dressing with compost to 1/2 inch.
Lawn Fertilizer Videos

“FALL LAWN FERTILIZATION“ by a turfgrass management instructor at Virginia Tech, explains why fall is the best time for feeding, and compares drop and broadcast spreaders. Mentions harm to waterways but does not compare types of fertilizers.
“FERTILIZING LAWNS” by Melinda Myers for Milorganite fertilizer. While promoting a particular product (organic fertilizer from processed sewage), we like that it recommends a low-maintenance regime for lawns that don’t have to look like golf courses – only need one fertilizer application each year, in the fall. It also shows how to calculate and apply the product.
“ORGANIC LAWN FERTILIZERS” by the University of Kentucky is a balanced answer to the question – “Does lawn care have to be organic to be safe for the environment? Advantages of organic fertilizers are: adding organic matter improves soil, no chance of fertilizer burn, and because they’re slow-release, low chance of run-off into waterways. The disadvantages are: more needs to be applied (because of lower nutrient concentration) so they’re more expensive not as easy to apply, and some smell bad. Cheapest source of organic fertilizer is grass clippings. Concludes that fertilizers do not have to be organic to be safe for the environment.
“ECO-FRIENDLY LAWN CARE“ by the University of Maine is very good. Its water quality scientist tells Maine residents to fertilizer around Labor Day. Says lawns over 10 years old “don’t need a lot of nutrients” beyond leaving clippings on lawn. And only add phosphorus if a soil test tells you it’s really needed (that saves you money and local waterways from pollution). Another of her eco-friendly tips: avoid weed/feed combination products.
“CHOOSE THE RIGHT GRASS SEED” by Cornell is an excellent summary of 4 main cool-season turfgrass types.
Lawn Repair Videos

“PATCH WEAK OR BARE SPOTS IN YOUR LAWN” by Cornell demonstrates a very easy method: mixing seed with soil/compost, and no straw needed.
“HOW TO PATCH A PROBLEM LAWN WITH SEED OR SOD“ by Dave Epstein recommends focusing on a healthy lawn, not a perfect one. Clearly demonstrates patching bad spots with seed or sod.
“CORE AERATION AND OVERSEEDING FOR A HEALTHY LAWN” by NaturalLawn of America demonstrates this often-recommended techniques for a healthier lawn, which should be done in the fall for cool-season grasses. We just had one question: if a homeowner doesn’t have a metal rake like the one shown to get good seed-to-soil contact, what else can they use? The easiest alternative they suggested is to simply rake over the lawn. Headquartered in Maryland, the company recommends applying seed from mid-August to mid-October.
More Great Info

For more information you can’t go wrong with the low-maintenance, resource-conserving lawn-care practices promoted by Cornell on their turfgrass website and their ebook “The Easiest Steps to an Attractive Environmental Asset.” Here’s a summary of their advice.
Water Less. Conventional wisdom is correct that grasses need about 1 inch of water per week, but only during periods of active growth. That means spring and fall, when there’s usually ample rainfall, anyway.
Then during the heat of the summer, cool-season grasses slow their growth and may even turn brown but are probably not dead. Studies show that as little as 1/4 inch of water over a three-week period can be enough to keep the sod alive. (Use a rain gauge to measure your rainfall. )
Feed Less. “Most home lawns with modest expectations do just fine with a single late-fall fertilizations mid-September to mid-October.” So for what Cornell calls “highest quality” turfgrass, several feedings are needed per year but for most homeowners, one application is plenty. Americans, does your lawn really need to look like a golf course? Time to adjust your expectations!
(Feed again in the spring only if the lawn is thin or winter-damaged, but wait until the soil has warmed up to 55 F.)
Are Organic Fertilizers Better? While they do introduce organic matter into the soil and that’s a good thing, synthetic fertilizers offer these advantages: you know exactly what’s in them, including zero phosphorus to protect waterways; they’re cheaper and easier to apply (because of the smaller quantity of product needed); and they can be applied at lower soil temperatures.
More important than the source of the fertilizer is whether it’s released slowly enough to protect the waterways from fertilizer pollution. So just choose a fertilizer that’s at least 30 percent slow-release (water-insoluble Nitrogen) for normal soils or 60 percent for sandy ones.
Weedkillers Probably Not Needed. The good news, according to lawn specialist Dr. Frank Rossi, is that the majority of public with lawns use no herbicides at all. But if hand-weeding isn’t doing the job he recommends selecting an herbicide that poses the least risk, as spelled out by the EPA in their list of over 100 herbicides.
The best defense against weeds, of course, is following sound lawn-care advice to produce a nice thick lawn and patching the bare spots, too.
Cornell also invites us to change our expectations for uniformity and just live with some weeds. They even suggest it’s time to rediscover the virtues of white clover – that instead of a weed, it converts Nitrogen in the air to a form the plants can use. So having clover means less need for supplemental fertilizer.
Mow Right. Cornell makes a big deal out of mowing correctly because it’s essential to preventing disease. They even go so far as to suggest that if you think your lawn needs a whole renovation, try mowing correctly for a year first because that may correct the problem.
So it’s about sharp blades, mowing high, and rather than the usual admonition to never remove more than a third of the blades at one time they recommend following the much easier “clump rule.” “Mow often enough to avoid piles of grass clippings. This might be every 5 days in the spring or not at all during summer drought and every 7-14 days the rest of the season.”