Indeed! Making a raised bed is the first step to creating an urban garden in the DFW area because not much is going to grow out of the soil here as it is. It's taken me 9 years of failure to finally grasp this concept: Few things will grow in the soil "as is" in this area of the country. It is far too clay impacted.
The easiest way to begin a raised bed is to build a frame and set it on top of the existing soil. Don't waste your energy digging up the soil underneath, even if it is grass. Instead, build a frame and pile 6 to 20 inches of amended soil inside the frame. (I don't recommend any frame with sides that are less than 6 inches high.)
Ideally the raised bed should not be wider than 4 feet in order to allow the gardener to have access all the way around the bed. Otherwise, your imagination is the limit as to how to construct the container for your raised bed. Most of them are square or rectangular in shape, but they don't have to be. For example, there are the keyhole garden structures which area kidney-shaped. For more detail on these structures, see this field guide.
Below is a photo of Ed Browning, a member of Loving Garland Green with two of his raised bed boxes waiting to be filled with soil. The one in the foreground is an old bookcase without the shelves. The one in the background was made from found lumber. Recycle, reuse whenever you can. You will save money and save the environment. I recommend driving around your neighborhood on Mondays and Tuesdays when people set their unwanted items out in front of their homes here in Garland. Within two weeks, I guarantee that you will have found all the items you need to build at least one raised bed frame. In fact, I literally did make a raised garden bed frame from an old bed frame I found.
Amended soil is soil that has been mixed with various ingredients to encourage healthy plant production. The various ingredients and their percentage of the mix consist of will vary according to what urban farmer you ask. Some, like Mel Bartholomew, the founder of the square foot garden method, will tell you the mix is 1/3 vermiculite, 1/3 peat moss, and 1/3 mix of compost and garden soil. Others will instruct you differently. I follow Bartholomew's mix to establish a bed and then add a thin layer of compost to the top of the soil every season. Healthy soil is light and fluffy. Heavy, clay-compacted soil such as we have in the North Texas area does not make for healthy plant roots.
The sucess of your garden depends on healthy soil. The more you do to keep your soil healthy, the more productive your garden will be. I like the mixture of 1/3 vermiculite and 1/3 peat moss because this mixture increases the retention of water in the soil while still eliminating the possibility of root rot.
All urban gardeners should have some sort of a composting system. Composting is a means of recycling almost any type of organic waste. Classic composting is labor intensive and requires frequent turning--but not so bad if you have a compost tumbler. There are two other methods of composting that are easier: Sheet Composting and Vermicomposting.
- Sheet Composting
Apply high nitrogen greens first directly on top of the ground where the microbial populations can feed on them. Cover the green layer with the coaser carbon browns (such as dry leaves). This layer acts as a mulch to prevent the nitrogen green layer from drying out.
Use earthworms to convert nutrient dense materials, such as manure and vegetable garbage from your kitchen, into healthy soil for your plants. A local worm expert is located right here in the City of Garland--Heather Rinaldi of the Texas Worm Ranch.
Mulching (covering the top layer of soil) is very important for several reasons--especially in our North Texas area. The soil in raised beds will dry out quickly in our 100 + degrees spring and summers. Covering the top layer of the soil with a mulch, such as straw or pine needles, will slow down evaporation and will also keep the soil and all the microbe community living there healthy and doing their respective jobs for your plants.