Does 100% sawdust work well?
If so, then does it matter whether it comes from natural wood
or from commercial lumber?
Unusual question. Does someone recommend this? Nothing grows in sawdust for good reason, plain or even mixed with other materials.
The wood dust binds up all the nitrogen to aid it in decomposition including leaching the nutrients out of the seed coat that the young seedlings need to survive. And if it did work yes, it would have to be sawdust from plain, natural, chemically untreated lumber. Most commercial lumber is treated in some fashion.
As usual Dave is right on the money. Sawdust leaches all the nutrients out of any plant. The only good use for sawdust in the garden is to add it to the compost heap but only if you know it's not treated in some way like chippings from a downed tree. Otherwise it is best to send it to the landfill or use it on paths away from any plantings
Thank you for the replies,
on the strength of which I dismiss my tentative thought of trying it.
( Before I posted the question, I had searched GW for information. I cite the
following only as a for-whatever-it's-worth perspective, given the different condition.
"...sawdust (several years old).... seeds germinated, and within a couple of weeks were 6 TIMES (Yes I measured them!) larger than the seedlings in the flats"
Comments taken out of context can often be very misleading. As was pointed out in that discussion of potting mixes, that individual was having a number of problems with their methods.
The important distinction in that thread is that it was well rotted sawdust - several years old - mixed with compost.
While we don't have anyway of knowing the ratio of compost to rotted sawdust that one person used we can guess that it was predominately compost as it was used to fill an in-ground bed.
The primary point was how well rotted it was. Any sawdust, over years of time time, will break down to the point where it no longer binds up nitrogen and becomes a neutral soil amendment. Does that mean it should be used to start seeds? No,
You didn't stipulate the age of the sawdust in your original post.
Hope this clarifies.