30-year-old hardwood sawdust for compost?

Stewart, TN

There used to be a sawmill nearby. It was abandoned thirty years ago and the mounds of hardwood sawdust are available. Can I safely mix it or layer it with composted leaves and lake muck (leaf mold and silt) for my raised beds? Thank you for your help.

Dillon, SC(Zone 7b)

Many years ago I had access to a large mound of sawdust that was 30 or 40 years old. I put it directly into my garden to help loosen my heavy clay soil and it did just fine. If you combined it with composted leaves and silt I would think it would be perfectly safe to use immediately in your raised beds, especially since it's hardwood sawdust. The stuff I used was probably pine, but it had aged enough that it didn't seem to hurt anything I was growing.

Stewart, TN

Thank you, sos - it's not the kind of question everybody can answer! (You know, I used a little of it already to patch up holes where some creature had been digging for grubs, and it seemed to discourage whatever it was from returning - perhaps it has just enough sawdust smell to not be appealing. An extra dividend. )

Milton, NH(Zone 5a)

I used sawdust in my first ever compost pile. I used about a two 5gal. buckets filled with a mix of hard and softwood sawdust. It was new sawdust. I mixed it in with my supply of straw and added my nitrogen mix, water, and mixed it all up with air. I was surpised that after 3 months, the sawdust had broken down into dark compost much while the straw needed more time.

Milton, NH(Zone 5a)

You might have to increase your nitrogen source. I'm having good results with alfalfa pellets. Reasonably in expensive and less attractive to scavenging critters.

Stewart, TN

This information is all very interesting. I am trying to study and understand it. A neighbor warned me yesterday that the sawdust pile I have been raiding is not 30 years old but only about 6 years old. He has a truck farm and he says that this sawdust will not grow vegetables. When I was digging it, it looked like good dirt. You can't really tell it used to be sawdust except for a faint sawdust fragrance. However, it only had weeds on the top and not on the sides, a fact which may be significant.

I guess I'm trying for a compromise. In filling my latest raised bed, I put down about four inches of sawdust, then a layer of newspaper a la "lasagna" gardening, and now I'm going to add about four inches of lake muck, with a little leaf compost and bagged potting soil on top. It's for lupine, larkspur and poppy seeds. Whaddya think?

Austin, TX(Zone 8b)

lol - Yeah, always good to chat up the neighbors... I'm guessing he's saying you can't grow vegetables in _just_ sawdust, no matter how much it looks like soil. I'd say you're on the right track with mixing, but he sure sounds like a solid local expert. (Although if it were me, I wouldn't bother with bagged potting soil, just excavate down a little bit to get the native dirt.)

Was there something in particular you're trying to fix with your soil? I would have guessed that it was pretty deep and fertile from the river.

You might look into using native flowers where you can, since obviously they're already prepared to live in your soil. (Even the sawdust amended soil - that's sorta just a speeded up version of a tree falling in the forest.)

Keep us posted...

Btw, in your layering, newspaper is basically the same material as sawdust, just in little particles instead of thin sheets.

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