06/03/2026
Elevating the View of Raised Beds
An exciting idea with several important pitfalls
Raised bed gardens are a popular way to grow vegetables, particularly in the Midwest with soils that are dominated by clay. Raised beds have some real advantages over in- soil gardens but there is no free lunch, no magic bullet to solve problems without creating other concerns
Here are some important considerations when building a raised bed garden.
Advantages
Rather than struggling with our region’s notorious clay soil, a raised bed garden can be instantly fertile, well drained and safe from contamination in the parent soil. This can be important when gardening in the urban environment where there can be dangerous legacy problems. With a raised bed, the location is more flexible. If your concrete patio gets the best sun, you can put your raised beds there. With raised beds you can have lawn between the beds. Elevating the bed for more comfortable gardening is one of the biggest pluses that raised beds can give.
Considerations
None of the above comes without a trade-off. The best system is one that best fits your needs and budget. The problems I’ve seen come from wanting a particular design without understanding the limitations that design may deliver. I’ve listed some things to consider below.
Cost
The higher the bed, the more materials are needed to build and fill the bed and the more they’ll cost. Ask yourself the big questions. How many fresh vegetables could I buy with the money I’ll spend on these beds? How many more vegetables could I buy if I avoid the costs of seeds, soil, tools, fertilizer, etc? Finally, what could I do with the free time I’ll have when I’m not gardening? Since gardening is baked into some of us, the costs are just a part of life. For many, the appearance of the garden is a critical part of the landscape and deserves to be more decorative (and expensive).
Height
If you’re still with me, there are several things to know about building a raised bed.
It’s very attractive to want a garden that is so tall that it eliminates all bending over. There are lots of container systems available that provide for a 2-3 foot tall garden bed.
But what do the plants need
Roots need 12 inches of good soil if you’re growing carrots but 6 inches will suffice for most other crops. A low raised bed will have contact at the bottom with the native soil. That soil will eventually be loosened and transformed by the compost juice from above and the roots will be able to use the parent soil for resources.
Building beds with sides taller than 12 inches will require another choice! Fill the bed completely with expensive compost or raised bed mix or….2. Build up the lower level with wood, sticks, hay or other cheap organic materials, all the while knowing that your bottom layer will rot and collapse eventually sending you back to number 1 (above) for more expensive soil.
Compaction, erosion and plants eating the organic matter in the soil means that you’ll need to add more soil every year anyway, so you may still choose the tall beds.
Height adds another problem. The earth usually stays cool enough for plants to grow .(less than 80 degrees) A raised bed ,particularly if it’s tall and narrow, can be too exposed to the summer air and get too hot to grow plants. (Ask me how I know about this)
My advice is no beds narrower than three feet and if this is a possible problem turn the long side to an east west orientation. Long summer afternoons will create extremely hot conditions on the west-exposed side of the bed and transmit that heat inside.
Width
My favorite raised bed is a 4 feet wide and 8-16 feet long by 10 inches high with a 2X6 top rail to sit on. This allows the gardener to sit comfortably and reach the middle of the bed. This results in a bed so wide that it has great contact with the earth and won’t get too hot.
Filling the bed
Filling this relatively low bed is an easy call with either raised bed mix or a mix of good compost and top soil. My preference is to have some of the native soil in the mix even though it’s not the most fertile. Compost is loose and fluffy and can fail as a substrate to anchor your plants. Clay is a terrific source of minerals and the more life in your soil the more available those minerals are.
About Compost
Compost is usually an industrial product that gets very hot and highly bacterial during decomposition. As such it can often rather devoid of life. It sounds crazy but after 6 weeks at 160 degrees only dormant bacteria exist in the compost. It can also dry out and be hard to moisten (hydrophobic). Most compost needs a long curing time to restore a wide range of soil creatures, especially fungi to the soil. A good organic fertilizer in usually the best way to make your bed fertile on day one. The health of your raised bed’s soil will improve over time, but you can’t snap your fingers and say “grow.” It doesn’t work that way.
Bagged compost from a box store usually tests very poorly and should be avoided. Compost made with food waste is the most nutrient rich I’ve tested. Making your own compost is the best but it’s practically impossible to make a large quantity of compost with just the organic matter in a yard. Even if you save all the leaves and compost all the food scraps you generate, (lots of additional work) one to two cubic yards of finished compost per year from a yard is a big yield. Buy your compost from a local supplier that avoids plastic contamination and uses a variety of ingredients. Food waste is a great ingredient but comes with contamination problems of its own. Just be aware that no two composts are alike and ask questions about how it’s made.
Compaction
The level of the soil in your bed will go down. First, compost is 30-50% organic matter and organic matter is plant food. The plants feed on it and it is gone. Exposure to direct sunshine will slowly oxidize (burn) the organic matter in your soil. The fine particles of organic matter will float away and be carried through and around your bed. Finally with rain and gravity the small particles in your bed will compact or compress together. This leaves your soil devoid of air spaces and hard to work.
You can till the surface with a hoe but correcting compaction with a hoe won’t work.
The broad fork can gently lift and aerate the soil without destroying the structure.
My favorite move is to put down a 1-2” layer of compost and then lift and aerate with a broad fork. The compost will fall into the cracks deep into the bed and help keep the air spaces open for a while.
And So
The desire to grow at least some of one’s food is strong. Your produce will have superior flavor and nutrition compared to the mass-produced stuff in the grocery store. The rapid growth of local food systems is evidence that people want a better option. I hope this blog prepares you to make your best choices on your way to a productive garden.
