Question
Hi I had a 45ft. evergreen tree removed and the trunk ground. There are alot of wood chips mixed in the soil, can I plant grass on it the way it is after it settles.Or do I remove some of the wood chips and put more soil.I have been told if I leave the wood chips I will have mushrooms growing.Also is it wise to leave it till next spring before I plant grass

Answer
The good news is the Mushrooms, which you know about.  Yes, that is the good news.  Because there is bad news.

Ready for this?

The decomposing wood is going to suck up Nitrogen for decades to come.

Depending on how much is left there and what they did and did not grind up.

Wish you'd asked first.

You have Tree Stumps.  You have Tree Roots.  Trees are Wood.  Wood is Lignin.

It takes YEARS for Lignin to decompose.  Underground, it takes MORE YEARS.  If you keep the area dry, it takes EVEN MORE YEARS.

10 years ago, forest products technology expert Charles Carll and pathologist Terry Highley addressed wood industry professionals on 'Decay of Wood and Wood-Based Products Above Ground in Buildings'.  They pointed out: 'Fungal hyphae secrete extracellular enzymes and other agents that depolymerize Wood cell wall materials.'

Brown-Rot Fungi belong to the Basidiomycetes Fungus family; they tend to favor softwoods -- Pines, Spruces, Fir Trees.

Researchers quickly observed that these Fungi need warmth and moisture to work:  'Most wood-inhabiting Fungi will develop only between 15 and 40 degrees C.  Optimum temperatures for most wood-decay Fungi are between 21 and 32 degrees C' (that's 70 degrees F to 90 degrees F).

When they looked at temperature preferences for Fungi, they found none functioned in an environment that was 54 degrees or cooler.  Most of these Fungi completely ceased growing at 104 degrees F.  Presence of some Yeasts at optimal temps, with optimal moisture, accelerates the decay work of some Fungi.

Younger Trees rotted faster.  Reason being, they did not have the rot-resisting waxes and tannins found in older specimens.  Ground woods rot faster, but the effects, while more short term, are more intense.  Because it contains so little Nitrogen, sawdust tends to cause Nitrogen immobilization in the Soil; the microbes that break wood particles down consume it all.

Amazing, the things they know these days.

Moral: Get to know and LOVE your Brown-Rot Fungi.  They and they alone are now in charge of making your evergreen tree stump vanish without a trace.  Which is why, incidentally, in case this is not already obvious to you, it would be suicide for you to try to eradicate Mushrooms and Fungi with Fungicide.  Do that and you'll be destroying the Lignin decomposers you need to break down those wood chips.

Some lesson for you on Fungi: They are ALL aerobic.

They ALL need moisture to work.

Wood decays fastest at higher temperatures.  Below 50 degrees F, decay slows considerably as Fungi metabolism drops.  At even lower temps, Fungi go dormant and all work comes to a halt.  Cornell University scientists at the School of Engineering have studied ways to speed up the way Fungi break down the Lignin in wood.  The school published their findings, 'The Effect of Lignin on Biodegradability', and posted them online:

http://compost.css.cornell.edu/calc/lignin.html

They say:  'Adding small quantities of Nitrogen to woody materials can increase Lignin degradation rates.'  We know that Bacteria participate in this feast, but we don't know -- yet -- exactly how or what they do, or even which ones select it.

Other authorities point out the Sugar is the perfect White-Rot Fungus food; 'feeding' those areas will help to accelerate breakdown of wood.

Still, this is daunting.  There has got to be a better way to get rid
of those stumps.  James, don't even THINK about putting a foot or two of topsoil over those areas.  Submerging them in Soil will slow down decomposition (your great grandchildren may still be dealing with this problem) by severely limiting the Oxygen available to those aerobic Fungi.

Any Grass you plant at that site is in danger of failure.  Grass almost always fails when planted over old Trees that are no longer there.  There are a LOT of people with this problem, and a bad case can last for DECADES.

There are a few steps you can take to minimize the side effects while this Nitrogen drama is unfolding.  For one, you can keep the region moist to support continuous consumption.  For another, you can monitor Nitrogen needs and supply it -- organically, please -- at first sign of Yellowing Grass.  If however you have the option of removing the Woodsy Soil in that area, and composting it in the corner of the yard for future use (in which case it will be quite spectacular), go for it and replace it with Soil that is un-tainted.  Still, you should continue to watch for signs of N deficiency, year after year, as the softwood roots that remain deep underground are still going to need what they need to disintegrate into dust.

Capeech?

Your followups invited.  Thanks for writing.

L.I.G.