They eventually decompose. There might be a depression when that happens, but if they are mounded up high, maybe not; hard to say.

The question is: what do you plan on doing with that space? Anything? If trying to replant, I'd haul them away and replace with topsoil. If nothing, just leave them.

How fast the stump grindings decompose will depend on their size, your climate and general soil conditions. All stump grinding I have been experienced with resulted in sawdust rather than chips and smaller particle sizes decompose faster than larger ones. Soil moisture and overall temperatures will also influence the rate of decomposition with warmer, damper conditions hastening the process. And the more biologically active your soil (populations of microrganisms, worms, beetles, etc.), the faster the process.

Any decomposition results in shrinkage of initial volume so some holes/depressions are to be expected. Ditto from any large roots remaining in the soil....these will eventually rot away, often leaving extended shallow depressions but are easy to fill.

I would not automatically exclude this area from future planting nor necessarily recommend you remove the grindings. Because of shrinkage you may need to add additional soil to maintain a desired level and any nitrogen-rich fertilizer will speed up the decomposition process as well offset any nutrient tie-up in the immediate area.

That small of a trees I bet you can plant five to ten feet from the stumps instantly with few problems. i also from experience bet it is 3 years or so until the are right at the stumps is serviceable for grass. you'll get some mounding and mushrooms maybe and some divits as the roots decompose

I think the bigger question is, why did 6 25 yr. old Norway spruce have to come down? OK, just kidding, but I'll bet they were some pretty nice trees at that age class.

Of course all will decompose. Others have covered the basics. And Ken nailed it, in that, for some, with postage stamp-sized yards, etc. where every square foot must be used now, this would not be acceptable, but for you, with your larger area to work with, certainly you can allow things to break down over time. And yes, some additional soil may well be needed to bring back to grade. Conifer chips often do support some pretty interesting fungal decomposers.

+oM

Concern:

Wood chip mulches will

tie up nitrogen and cause deficiencies in

plants.

Evidence

: Actually, many studies

have demonstrated that woody

mulch materials increase nutrient

levels in soils and/or associated plant foliage.

http://puyallup.wsu.edu/~Linda%20Chalker-Scott/Horticultural%20Myths_files/Myths/magazine%20pdfs/Woodchips.pdf

My problem with arborist (fresh) wood chips is that when they mix with soil, they sour the soil and don't let it dry out. The soured soil cannot grow much in it. The plants die for lack of oxygen.

That is why I suggest they be removed if the area is to be planted. It does depend on how much there are though.

After several years (assuming there are no huge submerged roots and stumps buried way down), the area becomes an excellent place to grow things.

The concept of "nitrogen drag", the temporary tying up of N via decomposing organisms, is much ballyhooed, but rarely demonstrated. That said, I wouldn't plant a new tree in a pile of stump chips, which around here anyway are a roughly even mix of soil and wood, and expect good success. But I disagree with the "souring" concept. If you are in, for purposes of this thread, an area with circumneutral soils, that is, soils having roughly a pH range of 6.5 to 7.5-I happen to live in such an area-woodchips and compost from local sources will reflect this range of pH values to a great degree. Some folks here think they are acidifying the soil by using "Christmas tree mulch" but it t'ain't so. Due to the very high buffering capacity of our soils here, which contain much clay and silt, the pH easily holds remarkably steady. Even legitimate soil acidifying methods, like using soil sulphur, are amazingly temporary.

Finally, any N that is temporarily held and used by the bodies of the bacteria and fungi breaking down woody debris is returned at the end of these organisms lives. It's not being robbed, just borrowed. Hey, I think all life is doing that!

+om

I'm not talking about pH when I say 'souring'.

The soil just begins to stink like a bog. It doesn't dry out, there's no oxygen. It's like a compost pile that's kept too wet and is never turned. That's all I'm saying. You can also observe steam on cool evenings. Not good for live plants.

And like I said, it depends on the depth of the chips. It may even depend on what kind of chips. My experience has been with hardwood (red oak, maple, and tulip poplar to be specific).

If you have a very large tree, you still have an impervious submerged 'platform' of roots/stump way down that the grinder could not reach, and then you have the thick layer above. This creates a dead zone in between where water cannot drain.

It takes about two years for them to break down ( longer for the remaining stump) to the point where oxygen, worms and whatever, move in again. Then, like I said, it's a GREAT place for planting.

Gotcha Dave. Sour is often used to mean acidic, though most folks don't probably realize that when they use the word. But I see what you're saying. For my part, I would never advocate purposely mixing uncomposted woodchips into soil. As a mulch layer over the top-yes, of course. But not mixed in.

The other problem with bark or woodchip mulches is their tendency to form a hydrophobic mat. It seems that some of these beneficial fungi which colonize the chip layer, over time, glue the whole thing together with their mycellia. I've already seen it where you can lift an entire tree ring of mulch with one hand like it's all one-piece. The only reasonable method for dealing with this-so far as I'm aware-is to get your three-prong cultivator out and gently work the stuff up. That also freshens its appearance. We use wetting agents to water some of our ornamental plantings in areas where stirring up the mulch isn't feasible, but I wouldn't expect the average homeowner to be purchasing wetting agents! BTW, some folks claim just your general-purpose dish detergent will "work just as well" as the expensive pro stuff. I can tell you from direct experience that's not necessarily so. The big manufacturers of consumer goods like dish detergent vary their recipes as different supplies come and go, or as ingredient prices rise and fall. So you never really know what you're getting. At least with professional wetting agents, they are what they say they are. And it is possible to find relatively low-cost ones, relatively being the operative word there.

+oM

I happen to have moved into a house where the previous owner (in a fit of pique after tree damage during a storm), had all trees on the property cut down (sad, isn't it?). This was about five years ago. I am however, utilizing the huge mounds of sawdust/chip/decomposing matter as a lovely place to plant things that like woodsy well drained soils. Many forest ephemerals seem to like it. My soil is quite non-well drained...so it's a plus for me to have these enormous ring around the old stumps to plant in. Odd as it looks.

I can see that. FWIW, we used to heal in our bare-root tree stock, this prior to planting them out, in stump chips. It was nothing short of amazing to see the mass of fine root growth in that substrate. I'm thinking the relatively low nitrogen environment was partially responsible for the explosion of feeder roots in that stuff. Not to mention its texture and degree of aeration.

+oM

Wood chips don't crust up like bark or sawdust, that is one of their advantages. Here they are sold by bark and soil dealers as a play area surface.

Unfortunately when they grind the old stump out, they produce chips, sawdust, bark chips and mix it all in with the soil. It's not like a clean bag of fir bark you might buy at the store!

Hey all,

Thank you for your advice. We had the stumps removed last week. I removed a lot of the wood chips, but there must be thousands of them. I also pulled up a ton of roots that were above ground with my digging bar, and I cut some of the larger ones below the top level with my saw. I then spread the soil out evenly with the rest of the yard, but a lot of wood chips are still mixed in with the soil.

I bought about five pounds of bulk perennial grass seed from a local hardware store for $13.50 and figured what the heck, I might as well try spreading it around. Based on what you have all told me, I doubt if the grass will grow, but hey, you never know. It would be great if we get some mushrooms. You just can't beat the taste of fresh mushrooms from your yard on a nicely grilled steak!

Do be sure to properly ID those shrooms! Many are safe, quite a few are tasty, and a handful will make you die.

+om