How do I keep a renovated lawn thick?

A renovated lawn stays thick when the new grass gets the first few weeks right and the routine after that favors grass over weeds: mow tall, feed in fall, water deeply rather than often, and patch thin spots every fall before they turn into bare ones. Here is what to do, in the order you will need it.

The first month: water

New seed has no reserves. After seeding, water lightly and frequently until the seed has germinated and established, avoiding so much water that seed washes away or drowns.^[1] Newly seeded lawns need more frequent watering for the first three to four weeks;^[2] in warm, dry weather that can mean a short watering more than once a day. As the grass fills in, gradually cut back the amount of water to start building a deep root system.^[1]

Stay off the new lawn as much as you can, and keep pets and kids to a path. Remember too that seedlings and lawns less than a year old have little to no drought tolerance,^[2] so the first summer is the one to watch.

Mowing

Start mowing as soon as the grass needs it, on firm soil, and never remove more than one-third of the leaf blade at a time.^[1] For fescue, Henrico County's Extension office says to set the mower at 3 to 4 inches for fescue lawns,^[3] which shades the soil and holds back weeds. Keep the blade sharp: a dull blade tears leaf blades, which can lead to disease or insect attack.^[3] Our guide to mowing height for fescue has more.

Leave the clippings. Returned clippings supply about one-fourth of a lawn's annual nitrogen needs and do not contribute to thatch.^[3]

Fertilizing

A new lawn needs feeding to thicken up. Newly established lawns or lawns that lack density benefit from properly timed nitrogen until they reach the cover you want.^[4] For tall fescue and other cool-season grasses, the time is fall: Virginia Tech's shorthand is "SON," for September, October and November,^[1] with up to 0.7 pound of water-soluble nitrogen per 1,000 square feet every four weeks,^[1] and never fertilize frozen soil.^[1] For a sense of the yearly total, Henrico's guide says tall fescue needs about 2.7 pounds of nitrogen per 1,000 square feet per year.^[3]

Go easy in spring. Virginia Tech advises cool-season lawn owners to avoid large spring applications of nitrogen,^[2] and fertilizing in late summer or early fall instead favors root growth and better drought tolerance.^[2] Base phosphorus, potassium and lime on a soil test. Our guide to when to fertilize a lawn in Virginia lays out the calendar.

Weeds

The thickest lawn is the best weed control, but a new one needs protecting from the weed killers too. Virginia Tech says herbicides may typically be applied after the second mowing on new turfgrass, with some exceptions,^[5] and the label has the final word.

Watch the preventers. Henrico's guide notes that crabgrass preventers other than Tupersan also stop grass seed from germinating,^[3] so they cannot go down in spring where you plan to overseed. Likewise, seeding must be delayed two to four months after a preemergence herbicide for annual bluegrass,^[5] the kind applied in late summer. If you need crabgrass control on a spring seeding, Virginia Tech notes that siduron and mesotrione control crabgrass without harming germinating cool-season grass.^[5] More in our guides to getting rid of weeds without killing grass and why a lawn fills with crabgrass.

Summer watering

Once the lawn is established, change the habit. Deep, infrequent watering that soaks the root zone to a 4-inch depth keeps roots healthy and reduces weeds,^[2] while light daily sprinkling keeps roots shallow. As a rule of thumb, most turfgrasses need about 1 inch of water a week, from rain or irrigation, to keep growing in warm weather,^[2] but applying a full inch in one go is likely impossible on most Virginia soils,^[2] so split it into two or more waterings. Water early in the morning, a few hours before or just after sunrise.^[2] Night watering greatly increases the chance of fungal disease.^[2]

Every fall: aerate, overseed, clear leaves

Tall fescue, the grass in most Virginia lawns, has limited to no recuperative potential,^[6] so it does not spread to fill thin spots. Overseeding is how you keep it dense. Henrico's checklist says to overseed between September 1 and October 15 at 2 to 3 pounds of seed per 1,000 square feet, using turf-type tall fescue in sun and fine fescue in shade,^[3] and that core aeration is a must before overseeding^[3] so the seed reaches soil. For aeration itself, the same guide suggests fall aeration every two to three years for a regularly maintained lawn and every year for a high-maintenance one.^[3]

One caution on timing: severe gray leaf spot outbreaks have coincided with fall overseeding in recent years, and seedlings are more susceptible.^[5] Water new seed in the early morning, not the evening, and choose seed of the newer tall fescue varieties bred to resist gray leaf spot.^[5]

Leaves come next. Mow them into the lawn if they break up and sift down, or rake or vacuum leaves in fall so they do not pack down the grass over winter.^[3]

Every few years: the soil

Virginia Tech suggests you test the soil at least once every three years^[1] and lime only when the test calls for it. Keep expectations realistic: Henrico's guide tells homeowners it may take two to three years to see the full benefit^[3] of good care. If the lawn thins again in the same places, the cause is still there; our guide to why a lawn has bare patches helps find it.

Stop and call a pro if

• Patches of new grass collapse or die quickly in warm, wet weather, which can be disease.
• The lawn stays soggy in the same spots after rain, or water runs toward the house.
• Grubs, moles or other pests are tearing up the new turf.
• You want weed or insect control done for you; use a business with a Virginia pesticide license.

See all lawn and landscaping answers, browse lawn renovation services, or look up lawn and landscaping businesses around Blacksburg. If you would like a company to take over the care, describe the job once and local businesses quote it.