Raised beds on pavement is a strategy for gardeners with limited growing space. Learn how to grow food in raised beds on paved surfaces such as concrete or asphalt.
My first homestead on one-tenth of an acre was lacking in garden space. At the time, I was frustrated by this limitation. Now, however, I realize how lucky I was! It forced me to be creative and explore a number of food-producing experiments that I might not have tried otherwise.
One experiment that worked really well was building two raised beds on one side of my driveway. I had considered depaving this unused section of the driveway, but decided to build raised beds on top of it instead. See the next section for more details about that decision.
It was totally worth it! Even though my raised beds were in the shade, they consistently produced around 80 pounds of vegetables each season.
Through this experience, I discovered several keys to growing successfully in raised beds on pavement. We’ll look at those in this article.
For urban gardeners and anyone with limited yard space, raised beds on concrete can be a simple solution for growing vegetables, herbs, and flowers. With some planning and elbow grease, it’s easy to transform lifeless pavement into a vibrant edible oasis. In this comprehensive guide, we’ll explore how to build, fill, plant, and maintain productive raised beds on concrete.
Why Put Raised Beds on Concrete?
There are several advantages to elevating garden beds on hard surfaces:
- Makes use of empty space like patios, sidewalks, and driveways
- Avoid depaving and potential soil contamination
- Convenient for gardeners with mobility issues
- Warms up faster in spring for an earlier start
- Excellent drainage
- Keeps plants away from pests in the ground
- Allows control of soil quality and depth
Building up also helps concentrate your efforts in a small space. Focus on enriching the soil in your raised beds without improving the rest of your yard.
Should You Depave or Build On Top?
Removing concrete and asphalt (depaving) is better for the environment since it allows rainwater to permeate into the soil. However, breaking up pavement is extremely labor intensive. Demolition may also expose buried contaminants that could leach into your garden.
Constructing raised beds on top of hardscapes is much easier. You also avoid risks from potential toxins underneath. Start by thoroughly cleaning the concrete to remove any chemicals.
Building on top is a practical option for renters or anyone not ready to undertake a major depaving project. You can always rip out the pavement later!
Choose the Ideal Height and Length
Bigger is better when it comes to raised beds on concrete! Aim for at least 24 inches tall and wider than 4 feet if possible
Extra height provides more space for roots to spread out. It also holds moisture and nutrients better. Wider beds allow you to grow more without crowding.
Standard lumber like 2×10 or 2×12 boards work well for short beds. For a longer lasting raised bed, use thick timber, landscaping blocks, or bricks. Or frame it with boulder retaining walls.
Save Money On Fill With Hugelkultur
Filling a tall raised bed gets expensive, especially when using store-bought soil or compost. Stretch your dollar with the hugelkultur method.
Hugelkultur uses decomposing wood as a base layer. Logs and branches act like a sponge to hold moisture As they slowly break down, fungi release nutrients to fertilize plants.
Start by laying logs and sticks over the concrete. Crisscross chunky pieces for stability. Top with compost and organic materials like leaves grass clippings or aged manure.
Adding worms, compost, and native soil introduces beneficial microbes for healthy plant growth.
Take Care When Planting
Brand new raised beds need time to settle before planting. Fill beds in fall and plant the following spring if possible.
Start with quick-growing greens and herbs. Try lettuces, spinach, arugula, parsley, basil, and cilantro.
After the first year, you can grow more demanding vegetables like tomatoes, peppers, broccoli, peas, beans, and carrots. Just provide regular water and nutrients.
Maintain With Careful Watering and Feeding
The biggest challenge with raised beds on concrete is water retention. Without surrounding soil, beds dry out faster.
Use drip irrigation or hand water thoroughly once or twice a week when needed. Adding organic mulch helps conserve moisture.
Apply balanced liquid fertilizer every 2-4 weeks to replenish nutrients. Or brew compost tea to feed soil microbes.
Boost the beds each fall with fresh compost, manure, leaves, etc. And check drainage holes to prevent clogging.
Creative Raised Bed Ideas
Looking for inspiration? Gardeners have come up with clever ways to grow food and flowers in raised beds on hard surfaces:
- Frame beds with recycled wood pallets
- Upcycle broken cinder blocks for edging
- Stack flagstone or bricks to make walls
- Line beds with landscape weed barrier
- Use metal troughs, galvanized stock tanks, or tin buckets
- Try free-standing wire garden planters
With a bit of imagination, it’s simple to create abundant raised beds anywhere there is sun. The end result is a flourishing urban oasis, even on concrete!
Frequently Asked Questions
Is it safe to grow edible plants in raised beds on concrete?
Yes! With proper precautions like gravel drainage and quality soil, plants thrive in raised beds on hard surfaces. Avoid chemicals leaching from pavement by using a barrier.
How tall should a raised bed on concrete be?
For adequate root room, beds should be 24-32 inches deep. Greater height holds more soil moisture and nutrients. Plants also receive better drainage.
What’s the most affordable way to fill a raised bed on pavement?
Reduce fill costs with the hugelkultur technique. Layer logs, branches, and other compostable biomass on the bottom before adding compost and topsoil. As the wood slowly decomposes, it holds moisture and provides nutrition.
How often do I need to water a raised bed on asphalt or concrete?
Expect to water more frequently, up to twice weekly, since beds on pavement dry out faster. Using drip irrigation makes watering simple. Adding thick organic mulch also conserves moisture between waterings.
Should I put gravel at the bottom of a raised bed on pavement?
Yes, it’s recommended to line the bottom with at least 5-6 inches of gravel. This creates a drainage reservoir, preventing waterlogged soil. Landscape fabric on top of the gravel helps separate the soil.
Raised garden beds on concrete open up a world of possibilities for urban gardening. Follow these tips and with a little sweat equity, you can grow thriving vegetables, herbs, and flowers even on the harshest hardscape. Let your creativity run wild!
How Tall to Make Raised Beds on Pavement
Your crops need room to stretch their legs and send their roots down, down, down. The deeper the raised bed, the more room crops have to grow a strong foundation. Say ‘no’ to floppy plants!
A deeper bed also helps crops to be more self-sufficient. That’s right! It holds moisture longer, which means less watering. In addition, crops with more and deeper roots can access more nutrients in the soil, which means less fertilizing.
Therefore, I recommend a raised bed that is a minimum of 24 inches tall and an ideal height of 32 inches. The taller the better! My own raised beds on my driveway were 24 inches tall, and they performed well. But they conserved water by being partially shaded.
In full sun, a taller raised bed will likely perform better in hot summers.
That’s a lot of raised bed! How do I fill a raised bed on pavement without breaking the bank?
Filling raised beds on pavement is a bit different than filling raised beds on permeable ground. To decide how to fill the bed, we need to understand how rainwater behaves inside a raised bed on pavement versus a raised bed on the ground.