Using Dirt in Grow-Boxes – or Growing Right In the Dirt

To further clarify my last post, most of the time we grow right in the existing dirt, with no soil amendments – no matter how “worn out” or “bad” it is.  Whether you have heavy clay or straight sand, or enything in between, unless the soil is diseased, toxic, or under water you can grow a great garden right in the soil.

However, “If for some reason you really must use Grow-Boxes, because you have no ground, but only a driveway, patio, or rocks, (or if you just want the many benefits offered by Grow-Boxes) then go for it. But DO NOT USE dirt in the Grow-Boxes!”  Following are a few of the many reasons not to use dirt in Grow-Boxes.  I recommend you save this information if you are contemplating that method of growing.

Grow-Boxes are designed to give you an excellent growing environment if you can’t grow in the dirt.  They involve an investment of both time and money, and therefore you should obtain the maximum benefit from their use.  If you put dirt from the garden in Grow-Boxes you defeat some of the reasons for having them in the first place, such as:
1) There are always multiplied thousands of weed seeds lying dormant in the dirt, just waiting for conditions favorable for sprouting.  Putting dirt in a Grow-Box creates that favorable environment, and you will have thousands of weeds, instead of NONE as you should.
2) The likelihood is also high that there will be some bugs and/or disease organisms in the dirt you use.  Put it into your Grow-Box, and suddenly instead of a pristine environment, you have the same problems of fighting bugs and disease as if growing in the soil.
3) By putting dirt in your Grow-Box you have the problems of clay soil, too sandy soil, etc., etc. – again minimizing the benefits of the Grow-Box environment.
4)  The weight of dirt in the box is between 2,000# and 2500# in a single 18″ X 30′ X 8″-high Grow-Box if used exclusively, and much more when saturated with water.  This will put substantial outward pressure on the box, and you will end up re-building your box many times over the years.  On the other hand, using sawdust and sand, I’ve seen Dr. Mittleider’s Grow-Boxes still perfectly usable after 25 years!
 
PLEASE, don’t try and figure out the best methods by trial and error!  It’s been done for you by the best!  Follow the procedures accurately as outlined, and you will have great success.

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.