Types of Sawdust to Use

To all Sawdust users:
 
Some folks think that because Cedar or other kinds of bark are used to keep weeds down, sawdust from those sources will be bad for plants.  This is not the case.  Bark and other types of mulch inhibit weed growth primarily by denying light to emerging weed seedlings. 
 
On the negative side, mulches also encourage garden pests and diseases by giving them a cool damp place to live and multiply.  We recommend you keep your garden clean, clear, and dry, except at the root zone of your plants. When you plant according to the Mittleider Method the close-planted vegetable plants will quickly shade the ground and minimize water evaporation, without any need for other ground cover.
 
Walnut sawdust is the only material – at least in North America – that we have found to be a problem for vegetable plants.

 

 

Will Sawdust & Peatmoss Decompose and Disappear?

Q. I was looking for a fertilizer substitute in my country (tropical), and I mentioned I was trying to grow in sand+sawdust mix. The person I talked to mentioned that the sawdust will decompose with time, leaving me with only sand.  I recall reading on your website that the planting mediums do not require to be replaced, but what he said made sense.  What are your experiences with this?

A. Organic materials will, indeed, decompose over time, and become less useful.  They do not disapear altogether, but you will need to supplement them occasionally.  Sawdust is slower to decompose, and thus useful for a longer time than peatmoss.  And perlite – if you can get it – lasts a very long time.  Coconut husks last well, but rice hulls decompose rather fast.

Dr. Mittleider has had the same Grow-Boxes in his backyard garden for over 25 years, and has never replaced the materials, to my knowledge. He has supplemented whenever necessary.  When we say the materials don’t need to be replaced, we mean that so long as there is no disease present, you can continue to use them – supplementing as necessary to keep the box full of soil mix.

Also, in a tropical country, organic materials will decompose faster than they do in colder climates, because not much decomposition happens when materials are frozen.

Replacing Soil-less Growing Medium

Q.  When I told someone I was growing in a sand+sawdust mix, he said that the sawdust will decompose with time, leaving me with only sand.  I recall reading on your website that the planting mediums do not require to be replaced.  What is your experience with this?

A.  Organic materials will, indeed, decompose over time.  They do not disapear altogether, but you will need to supplement them occasionally.  Sawdust is slower to decompose, and thus is useful for a longer time than peatmoss.  And perlite – if you can get it inexpensively – lasts a very long time.  Coconut husks also hold up well, but rice hulls decompose rather fast.

Dr. Mittleider has had the same Grow-Boxes in his backyard garden for over 25 years, and never totally replaced the materials, to my knowledge. He has supplemented regularly, however.

When we say the materials don’t need to be replaced, we mean that so long as there is no disease present, you can continue to use them – supplementing as necessary to keep the box full of soil mix.

Also, in a tropical country, organic materials will decompose faster than they do in colder climates, because not much decomposition happens when materials are frozen during the 4-6 months of winter.