"Right now, it's key to work on your lawn," says Jim Welshans, regional turfgrass educator at Penn State University. In fact, despite what many people might think, autumn, not spring, is perhaps the most vital time in many parts of the country. Welshans explains: "In Pennsylvania we grow cool-season grasses, and during the summer they're not very active." Come autumn, however, they revive.
Lawns with these cool-weather grasses — Kentucky bluegrass, fescues, perennial ryegrass — should be fertilized in two waves, say Welshans and others. The first application, from mid to late September in places like Pennsylvania, should be a fertilizer that's high in nitrogen. The second application, roughly about Thanksgiving but before the ground is frozen, should be a fertilizer that's high in phosphorus, which will prepare that plant for next year, says Welshans. (Exact timing for all the advice in this story will vary depending on where you live. A good way to determine if you're giving your lawn what it needs is to get a soil test. It will give you information like soil pH and nutrient levels, and provide recommendations for fertilizer amounts.)
Bob Mugaas, a regional extension educator in horticulture who's affiliated with the University of Minnesota, recommends modest application of nitrogen during the first couple of weeks in September, and a repeat application around Halloween in the Twin Cities area. If you missed the first window, don't fret, says Mugaas, but simply make the second application around Halloween. Why not squeeze in two doses in quick succession? "You don't want to stimulate the tender, succulent growth" as the grass girds for winter, he explains; the late-season application is more for the root system. Another tip: Homeowners can drive over leaves with a lawn mower to create a fine mulch as long as the results don't blanket the lawn.… Exceptions to the "fertilize!" rule are the desert Southwest and the Deep South — places like Georgia, Alabama and south Texas — where lawns generally have Bermuda, Zoysia, St. Augustine and centipede grasses. These largely go dormant in winter and don't need fertilizer, says Dave Han, associate professor at Auburn University and state extension specialist for turfgrass. "I cut off fertilizing in this part of the world about Oct. 1," Han says. Fertilizing can be extended along the warmer Gulf Coast, however, and you can feed grass year-round in south Florida and coastal Texas, he adds.
Now is a great time to repair a damaged lawn and reseed. If you're racing the cold, Welshans recommends putting down a perennial ryegrass, which germinates quickly (just four to seven days, versus two to three weeks for bluegrass). Help the seeds take root by top-dressing them with up to one-quarter-inch compost or soil, he says.
Though places such as the Pacific Northwest may begin to get rain with autumn's onset, in most areas watering shouldn't end with Labor Day. Generally speaking, says Mugaas, a lawn should get an inch of water every 14 to 21 days. The ground should be moist as it heads toward winter, but not soggy, which could encourage mold.
"Probably the most common thing I see people doing is pruning," says Ginger Pryor, coordinator of the Pennsylvania Master Gardener program, citing a common mistake. As a general rule, give your loppers and shears the autumn off. Why? Pruning promotes growth, and you don't want to encourage growth when plants are preparing to go dormant for winter. There are some exceptions, so call your local cooperative extension service if you have doubts about a particular tree.
Now is a good time to cut off dead wood, however, so insects have no place to hide.
"There are some great fall vegetables you can plant and still get a harvest," says Pryor. Many vegetables aren't affected by a light evening frost, so long as the days still warm up nicely. Greens like lettuce and spinach often can be harvested within 30 days of planting. Got even more time before Jack Frost really settles in? Think about carrots, broccoli or Swiss chard.
To prep your garden for winter, plant a nitrogen-rich cover crop like clover that you can simply turn under come spring, suggests Elaine Anderson, program coordinator for the Washington State University/King County Extension Master Gardener Program. Or, "a lot of people just cover the beds in burlap — keeps the weeds down. That's fine."
The experts agree: Autumn is a great time to transplant trees and shrubs. "By planting trees in the fall in the South we have a much longer season for the tree roots to get established" while they don't have "those other stresses" such as heat, explains Shane Harris, a regional extension agent in east-central Alabama who is affiliated with Auburn and Alabama A&M universities. In short, says Harris, the tree benefits because it's "putting all of its energy into root growth."
The same is true in other parts of the country. For example, as a general rule of thumb, evergreens should be transplanted in the first half of September in Minnesota's Twin Cities area, Mugaas advises. "Obviously you can be earlier if you're a little more north, or later if you're a little bit to the south," he says. "Deciduous trees have a little bigger window."
"We often say the mulch around the tree should look like a doughnut, not a volcano," says Pryor. Pulling the mulch away from the trunk a bit makes it less of a home and meal for voles, chipmunks and mice during the winter, she says.
Flower beds don't need a ton of work, but there are some things you can do. "One thing we do recommend for fall is cleaning out perennials — things that have a lot of dieback on them," says Pryor. In Pennsylvania, for example, there's a lot of rain in early spring and any dead growth can keep a lot of moisture in the soil, promoting rot in plants like peonies that have heavy root systems. (Other experts disagree about the importance of cleaning up but say it doesn't hurt, and at least can make a flower bed look tidier.) We recommend leaving ornamental grasses in place because they look beautiful in the winter & add visual interest in our QC area!