I would like to grow some plants this year round. I've been reading the book Square Foot Gardening, and have been enjoying the idea of gardening with this method. In the interest of creating a stable planter, I've modeled a block planter, 4' by 4' interior with an optional wood bench/overlay. In total it's built from 28 cement blocks and 10' 2" by 10" of wood.

I've found a price of ~$2 for the blocks. That makes the wood-free version about $60. I could likewise get 10 feet of wood for less than $15. $75 for a nice sturdy solid planter. Labor not included.

In the model, strings have been set into the wood. The string crevices could be more like shaved down in the real version. These strings are for distinguishing the individual squares of the garden.

If more garden space is needed, additional planters could be built nearby or in other appropriate places.