How to build garden beds

Fall is a great time to build a new garden

Kiran in Leesburg writes: “I have some questions about preparing a vegetable garden for next year’s growing season. Should I prepare the garden in the fall or spring? We have a lot of red clay; do I need to dig up what I have and replace it with top soil and organic compost? And do I use horse or cow manure? As you might guess I am new at this stuff.”

Fall is a great time to build the bones of next year’s garden, Kiran. It’s the most pleasant time of the year to be working outside; and putting the structure together now allows you to hit the ground running first thing next spring. (Or maybe even this year …)

Raise your beds above that clay

But no digging. Digging is for chumps — as is “flat earth gardening.” Instead build a couple of raised beds that will sit over the top of your lousy, clay soil and fill them with half compost and half black screened topsoil. Filling the frames with this rich mix of fresh soil will help you grow great plants and avoid any of the lead and other contaminates that could be lurking in your current dirt.

Use fieldstone, pavers, untreated wood or a composite material, such as Trex, to make frames that are about a foot high and no more than four feet wide so you can reach the centers of the beds without ever having to step on their perfectly loose soil.

Eight feet is a good standard length, but they can be as long as you want, just no wider than 4 feet. And be sure to leave a solid 2 feet of walking path in between each bed.

Prevent weeds up front

Get your framing material ready and have a big load of compost and topsoil delivered — a 50/50 mix of yard waste compost (not composted manure) and screened black topsoil is ideal.

Before you lay the frames out, use your lawn mower to scalp whatever’s already growing there — such as grass or weeds — down to bare dirt. Then remove any big rocks and such and use a shovel or garden fork to poke lots of drainage holes in that nasty clay soil.

Smooth out the surface with a hoe and then lay down single pieces of cardboard to block any new weed growth. Put the frames in place over the cardboard and fill them with the mix of compost and topsoil. You now have a naturally rich, weed-free surface to work with. Darned good looking, too!

Important: Never step on the nice loose soil in those beds! Soil compaction from your big feet is one of the biggest cause of poor plant performance. That’s why true raised beds are never more than 4 feet wide. If you don’t step on your growing areas, the soil doesn’t get compacted; your plants grow better; and you don’t ever have to till. Just add a couple inches of fresh compost to the top of the beds every season to keep the garden productive.

And very important for a first timer: go slow. Build a couple new beds every fall and you’ll soon have a full-scale, great-looking garden that didn’t break your back.

Keeping weeds down in the walkways

Because you’re not using your existing weed seed-infested soil, your actual raised beds shouldn’t sprout problem plants. To keep weeds down in between the beds, you can spread what are known as arborist wood chips (the kind that come from a tree-trimming crew, not that awful crappy dyed trash mulch) or use a weed-whacker or lawn mower to keep things tidy.

Cover your new beds with an inch or two of shredded leaves as soon as the trees start providing them (not whole leaves. They must be shredded.) to protect their soil over the winter. And/or start planting some things in the beds as soon as they’re ready. This is a great time of year to plant single cloves of garlic for harvest next summer, or to direct sow lettuce and other salad greens — they love growing in the cooler weather of fall.

Oh, and the manure answer is “neither.” Horse manure is very nitrogen-rich and really only suitable for lawns and sweet corn, not fruiting plants. And cow manure is collected from animals that were likely heavily medicated in a factory-farming environment. Feed your plants with compost, worm castings and gentle balanced organic fertilizers.

Time to start deflowering your edibles!

Seeing the kids heading back to school is a great reminder that time is running out for the crops of summer in our veggie gardens. The shorter hours of daylight cause plants to grow much more slowly, and whether you like it or not, you should turn your attention to the process of shutting some of them down. So:

  • Pull off any new flowers that appear on plants whose fruits take a long time to mature, like watermelons and pumpkins. Those flowers don’t have nearly enough time left to become big ripe fruits.
  • Inspect pumpkin and watermelon vines and remove really tiny fruits as well, ideally thinning each vine down to the three or four biggest and best looking fruits each.
  • You can certainly let cherry tomatoes continue to flower — those little fruits ripen up fast. Same with plants that produce small-to-medium-sized fruits.
  • But sadly, it is now time to start removing any new flowers that appear on big beefsteak type plants. (This will encourage your existing big green tomatoes to ripen up faster.)
  • Pull out underperforming or finished-for-the-season plants and use their space to sow lettuce and other salad greens (which grow best and taste the sweetest at this time of year). Pansies too! And, of course, cloves of garlic for harvest next summer.

Mike McGrath was Editor-in-Chief of ORGANIC GARDENING magazine from 1990 through 1997. He has been the host of the nationally syndicated Public Radio show “You Bet Your Garden” since 1998 and Garden Editor for WTOP since 1999. Send him your garden or pest control questions at

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