I'm sorry for the loss of your mother-in-law. That is a leach field that the contractors dug up to replace the septic tank. The overflow from the septic tank dissipates through the leach field. The leach field is part of the septic system, and costly to replace. It is supposed to be made of layers of sand and gravel.

You can put compost on top of the leach field, but you should not rototill the compost in. A layer of three to four inches of compost on top should be fine for growing a new lawn. Grass seed won't sprout in high summer temperatures. Fall is a good time for putting in a new lawn, whether it be sod or seed. The newly planted seed or sod needs to be watered daily for about a month to get a good start.

I wouldn't get rid of the old trees, but they could probably do with a good professional pruning. Definitely take out the volunteers.

Lorna

With maple trees, you're going to have a very hard time tilling or growing grass, period. Maples have shallow root systems that reach a long ways in all directions. When you till, the tiller will hit roots and throw you around all over the place. Grass will have difficulty growing, not just because it's in shade, but primarily because it will be competing with tree roots for moisture and nutrients.

If you have a bumper crop of weeds, you probably have enough sun to grow grass. I've found that weeds are amazingly able to grow in the most adverse soil conditions, such as competition with tree roots. However, most weeds like plenty of sun, with the exception of wild violets. They'll grow in the shade with no problem whatsoever.

I wouldn't just till in the weeds and then plant grass seed. The weeds will return just fine. I would kill them with Roundup first. And Lorna is right about not sowing grass seed now - it's too hot, and it will burn out. Wait til September.

Deanna

Along with the term "leach field" which is old and rarely used today (it is a drain field) is the idea that you should not till the area above that drain field. There should be a minimum of 18 inches to the drain tiles (more often 2 to 3 feet down and sometimes even deeper) that comprise this drain field, more than ample space to till in some compost which will greatly aid growing grass above that. A 3 to 6 inch layer of compost tilled into this soil will not be too much as long as it is not over tilled.

Thanks to all for the advice and recommendations.

Lorna - The old trees will be staying and getting a good pruning if we can find a decent arborist. The lines and new septic tank are minimally 2'-3' below ground. Is there another reason not to till the compost into the soil above the leach field other than concerns about hitting the septic system?

Deanna - I'm trying to stay away from blanket applications of chemicals and would prefer to go as organically as possible. The weeds will probably get pulled out or cut as low as possible and chucked into the fledgling compost pile.

Kimmsr - You are correct, the lines and new tank are all 2'-3' deep. I'm just a bit hesitant to begin the process since it means that I'll be hauling approximately 70 yards of compost to get the 6" layer that I'd like to have. How much tilling would be considered "over tilling"?

Given that you live in NY, I'm not sure I agree with the recommendation from NM that you wait until fall to seed grass. While it's true that fall and spring are the *BEST* time to seed grass, you can actually do it in the summer if you mulch it and provide adequate water. You sound anxious to put the house on the market, so I'd say go for it now. You can till it in if you want to, but 1) it's not necessary... you can just put the compost on top of the existing lawn instead and 2) you may end up with an irregular surface as a result of tilling, as soil material settles back into place.

If it were me, I'd either:
1) Put down several inches of compost, then seed, then mulch with 1/2 inch additional compost and be absolutely religious about keeping it moist for several weeks.

-or-

2) Wait until fall, then put down several inches of compost and then sod. Sod of course has the instant gratification advantage, so you could pretty much put the house on the market the next day (provided of course that you keep the sod well watered as per instructions).

-Diggity

Diggity - Yes, anxious would be our current state of mind, but it hasn't reached critical mass yet. We're looking at next summer as a target for putting it up for sale, but we may end up holding on to it as a rental property if the housing market stays like it is or gets worse :(

You are right about the grass. I did a couple of patches last week where there were some ankle-breaking holes and the grass there is looking great, so I may just go ahead and seed as soon as I can get the compost tilled in.

As for tilling in the compost, it could hardly make the yard surface any worse. "Irregular" would be a nice word for the way it looks now and I figure we have a few weeks of work to do just to get the largest of the rocks picked up.

Would it be counterproductive to go over the entire area with a roller after tilling in the compost? Better with an empty one or half full? Better to seed before or after rolling?

What would be "over tilling" is a bit difficult to say but when that is done the soil is a powder with little structure to it. Rolling is counterproductive and is not needed, unless one "over tills". Till your compost in, water well to settle that soil, and then seed. Grass seed generally germinates when soil moisture and temperature levels are agreeable and that most often happens in the fall, and spring. The reason that fall seeding is better than spring is that this new growth will have several months to get better established before the hot, dry summer weather will cause it to go dormant. Since the grasses you will be growing in New York wil lbe "cool season" grasses they simply grow better during cool weather and go dormant when it gets hot.

Thanks, kimmsr. If I'm understanding you, "over tilling" is something that I won't know I'm doing until after I've done it :) I'll just take it slowly, do a small section at a time, and try not to get carried away with the rototiller.

Some folks say rototilling is not a good thing for soil ecosystem, let alone shallow tree roots. From your description your leach field does not begin 18" down. Wisea$$ comment, maybe drain fields are laid lower than leach fields. ;-) It would be much less work and expense to simply layer on compost. If you do plant grass seed, when temperatures are still hot, you will have to water twice a day to keep things moist.

Kimm it was presumptious of you to claim that drain field is the preferred term. Having lived in three New England states, Idaho, California and New Mexico, I am well aware that lanaguage differs in various areas of the country. Leach field is the term used throughout much of the U.S.

As for old-fashioned, indeed, I am. Eisenhower was president when I was born.

Lorna

Lorna - While rototilling may not be the best thing for the soil food web, I think that the septic system work has done more damage than I could ever do with a rented tiller. Maybe I wasn't descriptive enough of the actual work that the contractors did and gave you an incorrect picture of the situation.

They dug a 25'-30' diameter hole that was about 20'-25' deep as well as a 10'-15' deep by 6' wide trench across most of the yard to connect into the waste pipe from the house. This work was done because the old 1950's septic tank had begun to collapse into itself and they also had to dig up the ground there so that it could be pumped out and filled in for safety reasons. All of the plumbing is at least 2'-3' below ground level. Whether this is a leach field or a drain field, I think it should be okay to pile 3"-6" of compost on top of the ground and till it in. Especially since I'll be doing a bit of re-leveling as I go along. The contractors had 2 large machines in the yard at different times (a combo front end scoop-loader/back hoe and a regular old bulldozer) and the end result was a yard that looked like a war zone. They were nice enough to offer to come back 6 months after the work was completed to "re-level" the ground where the work was done, but considering the damage the machines did to the asphalt driveway, front yard, and side yard, I think that I'd rather do it myself than invite them back.

Franklin D. Roosevelt was president and WWII was only beginning when I was born and back then "leach field" was what was used to describe a septic systems drain field. Anyone that works with such systems today will use the term "drain field" except those few that are still hung up in the olden times.
The guys that constructed that drain field did more harm to the soils ecosytem then spazboy ever will tilling it.