|I want to thatch and aerate the grass. What should be done first? When is the best time of the year to do it?|
|Thatching helps remove old, dead roots, stems and rhizomes from lawn areas, improves water penetration, and encourages new growth. It can be done in the late spring, followed by an application of fertilizer, to promote vigorous growth. To tell if your lawn needs dethatching, dig out a slice of lawn, roots, and a few inches of soil. Measure the thatch (dead stems and rhizomes). If it measures over 1/2 inch, it should be removed. If the lawn area is small, you can rake it vigorously to remove thatch. If the lawn is large, you may want to consider renting a power thatcher.
The soil under your lawn can become compacted from foot traffic, and compacted soil excludes air (which roots need). You can fix compacted lawns by aerating every 2-3 years in either the spring or the fall. If you rent a power aerator, it will dislodge plugs of soil. Leave the plugs on the lawn (they'll decompose and break down in the rain). After aerating, spread a thin layer of sand or organic mulch over the top of the lawn and then water deeply.
I think I'd thatch in the spring and aerate in the autumn.