How to Build a New Garden Bed This Fall in Oklahoma

Fall is one of the best times to build a new garden bed in Oklahoma. Build it now and the bed settles over the winter and is ready to plant the moment spring arrives. The recipe we recommend most often to the homeowners and landscapers who come through our Norman yard is simple: half compost, half topsoil, mixed through the whole bed, built on top of loosened clay and raised at least six inches above the ground. Get the bermudagrass out before you start, and put in a barrier so it stays out.

Why build it in fall instead of spring

• Fall is the best time for a soil test. Oklahoma State University Extension says so directly in its Raised Bed Gardening fact sheet, because slow-acting adjustments like lime, phosphorus, or potassium can be worked in before the spring planting rush. Your county OSU Extension office can run the test.
• The bed has time to settle. Freshly mixed soil settles over its first few months. Build in fall, top it off in spring, and plant into a bed that has already found its level.
• You beat the spring rush. Business at landscape supply yards, ours included, is quiet in winter and picks up fast in spring, and weather swings it even more. Material is easier to get and delivery is easier to schedule now than in April.

Step by step: building the bed

1. Pick the spot and size. OSU recommends a maximum width of about four feet, since most adults can reach about two feet in from each side, so you never step on the soil. Eight feet is a common length. Running the bed north to south gives the most even sun.
2. Clear the grass completely, especially bermudagrass. This is the step that ruins more Oklahoma gardens than any other. OSU notes that killing bermudagrass works best while it is actively growing, with late summer being ideal. By October it is slowing down, so dig it out thoroughly, roots and all.
3. Put in a bermuda barrier. OSU warns that a bed next to a bermudagrass lawn will be invaded within about a month without one. Bury a barrier material one foot deep, sticking up three to four inches above the soil line, around any side that touches the lawn.
4. Loosen the clay underneath. OSU calls double digging "very beneficial, especially in tight clay soils": spade the loose top layer to one side, use a spading fork to break up the deeper soil, then put the top layer back. It lets water and air move down instead of pooling.
5. Build the frame, if you want one. Treated lumber, landscape timbers, block, stone, or brick all work. OSU recommends against railroad ties unless they are well aged, since creosote vapors can burn tender plants. Unframed mounded beds work fine too; just mulch the sides so they hold together in heavy rain.
6. Fill it with the 50/50 mix. Equal parts compost and topsoil, mixed together or spread in alternating layers. OSU notes a bed filled with alternating layers of compost and soil "will make an ideal environment for plant growth." Raise it at least six inches above the surrounding ground; OSU says that alone greatly improves drainage.
7. Test the soil, then mulch the paths. Take your soil sample now while the timing is right, and cover the walkways between beds with mulch to keep weeds down.

Why 50/50, and not straight compost or straight topsoil

Each half does a different job. Topsoil gives the bed body, so it holds its shape and anchors roots. Compost adds organic matter and nutrients and keeps heavy soil loose and draining. Straight topsoil on its own is not especially rich, and straight compost is too rich and holds too much water to plant into. Our guide to compost vs. topsoil vs. garden soil explains the difference between the three materials in detail.

One more reason compost matters so much here: OSU points out that "Oklahoma's high temperatures rapidly decompose organic matter." That is why their advice is to keep adding a two-inch layer of compost every spring and fall after the bed is built. A garden bed in Oklahoma is never finished; it gets fed twice a year.

How much to order

Material is sold by the cubic yard. Here is what common bed sizes take when filled with new mix, split for the 50/50 recipe:

Bed	Fill depth	Total mix	Compost	Topsoil
One 4x4 bed	10 inches	0.49 cubic yards	0.25	0.25
One 4x8 bed	8 inches	0.79 cubic yards	0.40	0.40
One 4x8 bed	10 inches	0.99 cubic yards	0.49	0.49
One 4x8 bed	12 inches	1.19 cubic yards	0.59	0.59
One 4x12 bed	10 inches	1.48 cubic yards	0.74	0.74
Two 4x8 beds	10 inches	1.98 cubic yards	0.99	0.99

Calculated as length x width (feet) x depth (inches) / 324. Order a little extra for settling.

For other sizes, our material calculator does the math.

Mix it yourself, or buy it premixed?

We sell both, so here is a straight comparison at our current per-yard prices (before tax, from our pricing page):

Option	Cost per cubic yard	Best for
50/50 compost and screened topsoil, mixed yourself	About $51.75	Several beds, if you do not mind mixing
50/50 compost and regular topsoil, mixed yourself	About $48.75	Large beds on a budget
Rich Mix, ready to plant	$58.50	One or two beds, or anyone who wants to skip mixing

The honest take: if you are building several beds and have a wheelbarrow and an afternoon, mixing your own 50/50 saves several dollars a yard. If you are building a single bed, the savings are small, and buying two separate half-loads and mixing them is more hassle than it is worth. A ready-to-plant blend like our Rich Mix is the simpler call. Either way, you are not overpaying for bagged soil at the store.

Ready to build?

Clear the bermuda, loosen the clay, fill with half compost and half topsoil, and top it with two inches of compost every spring and fall. We carry compost, screened topsoil, topsoil, and Rich Mix by the cubic yard at our Norman yard, for pickup or delivery across Norman and the surrounding area. Tell us your bed sizes and we will help you get the amounts right: call (405) 826-2001 or stop by.