Q. I do container gardening. Cement blocks would match my landscaping plan better than wood. However, I’m guessing they would be difficult to keep straight over time. Is that why we are advised to use wood? I’ve also heard that cement blocks have some chemicals or minerals that leach out of them over the years. Is this part of the reason to not use them for Grow-Boxes?
A. Reasons for using wood for Grow-Boxes include the fact that
1) wood is available most everywhere, and
2) is relatively inexpensive;
3) it lasts a long time, if painted or treated;
4) it is easy to level, keep straight, and attach together;
5) it provides an attractive, uniform appearance to the garden;
6) it is non-toxic, so long as walnut is not used, and so long as treatment materials are safe.
Reasons for using cinder blocks instead of wood include:
1) If they are available – probably used – for free or at very low cost they can be less costly than wood.
2) They will last longer than wood, since they don’t deteriorate from water and bugs.
3) They may look better or fit into a landscape decorating scheme better than wood (or not!).
4) They give a place to sit when working in the Grow-Box
Reasons against using cinder blocks for Grow-Boxes:
1) Normally much more expensive to purchase than wood.
2) Take up much more space from the aisles (16″ wide instead of 2″ for wood).
3) Require filling with cement and rebar stakes in each block to keep them from moving.
Another alternative is cement frames. These are great where wood is unavailable, expensive, or subject to heavy termite damage, etc. They also work very well for commercial operations, because they last indefinitely and require very little maintenance. The Mittleider gardening books have examples of many different materials being used successfully for Grow-Boxes. They are available at www.growfood.com
Here’s how to install cement Grow-Boxes: Build a few frames for boxes 3″ thick and 8″ tall. Place galvanized barbed wire one inch deep in the fresh cement, to give strength and stability to the box. For fast production in pouring cement, make the inside frames in 2 pieces, breaking in the middle of the long sides. After only 2-3 hours these can be carefully removed and placed in the new location for pouring at least 2 boxes each day from 1 set of frames.
A short cement “curb” works well in growing seedlings, to keep seedling flats off the ground. This is 3″ high, 4″ wide on the bottom and 3″ high at the top. They are placed 15″ apart, so that 18″ flats have 1 1/2″ on each curb. Bailing wire is placed inside the fresh curb cement to give strength and keep the curb from separating if the cement is broken.