My handyman husband builds mine. He buys two 1 x 8-inch cedar boards, which don't rot with age. They come in 8-foot lengths, which is perfect for 4 x 4-foot beds. Cut each plank in half, so that it is 4-feet long. Or, you can have a home improvement/lumber store make the cuts. Many places will do it for free. My Handyman
Husband also buys a 3-foot length of a 1 x 1-inch pine stake; he cuts it into four pieces and uses them to nail the cedar boards to at corners for bracing. That's all!
I place the boxes on cleared ground. We cut and roll up our turf, but many gardeners do not think it is necessary. The added 6 inches of soil will bury most of the grass and weeds beneath. After I situate the boxes (four or five grouped together makes a good sized garden), I put down three layers of newspaper to suppress wicked weeds. Paper degrades fully within weeks and feeds the soil.
Cement construction blocks are a cheap method of building raised beds.
You will be planting seeds and transplants close, because the beds are smaller and the soil is richer. But, plants grown close together in raised beds mature faster, because they compete for nutrients and sunlight. Each plant senses the distance of others and adjusts its metabolism to compete. Several university studies have proven this competition syndrome by identifying how plants perceive others nearby using the green light spectrum.
This 4 x 4-foot bed is crowded with productive peppers, cucumbers, a tomato plant and insect-repelling flowers that are edible.
Raised Bed Soil Mix
The more organic matter there is in soil, the better. Soil microbes are fed, oxygen and water
readily reach roots and plants thrive. Here’s the recipe I’ve developed in the last decade that
works best for my garden.
For one 4 x 4-foot raised bed. (Multiply amounts to fill larger beds.)
2 bags (2-cubic-feet each) top soil
1 pail (3-cubic-feet) peat moss
1 bag (2 to 3-cubic feet) compost or composted cow manure
2-inch layer of shredded leaves or grass clipping.
If you use grass, make sure the clippings are not from a lawn that has been sprayed with herbicides or been fertilized with a food that contains granular herbicides to kill weeds. Both persist and will kill plants beds up to three years after the initial application.
Mix all materials with a hoe or cultivator and water well. Be sure to mulch well with organic Matter such as more leaves or clippings or straw.
reprint from Gardeners Almanac