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Gardening on Concrete With Raised Beds and Patio Containers

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Think you can’t grow vegetables because you don’t have a backyard? Think again.

By Eartheasy Posted Apr 21, 2017

Raised beds on concrete
With more than one in three American households now participating in some form of food gardening, the promise of fresh, local produce is closer than ever before. But not everyone taking part in this gardening revolution has an acre or two of arable soil tucked away in their backyard. In fact, many people driving up this statistic don’t even have a backyard—and they’re growing something anyway. So how do they do it?

With outdoor space at a premium, urban and small-space gardeners have embraced portable and often temporary garden designs to make the most of the space they have available. Whether confined to a balcony, patio, or other paved area, these gardens are sprouting up everywhere using two mainstays of the urban farming movement: raised beds and patio planters or containers.

Raised Garden Beds

While raised beds are most commonly installed on top of bare soil to improve garden health and accessibility, more people are discovering that with a few adjustments, they can also work on top of paved surfaces. Not only do raised beds provide benefits like ample garden space at a reasonable price, they also offer versatility for those with a larger area to fill.

Are raised garden beds right for you?

Raised garden beds
Raised beds are right for you if:

  • You have a larger space and you want to grow a plethora of healthy, nutritious foods.
  • You have materials available to construct sides for your beds or you’re able to purchase ready-made raised garden bed kits.
  • You have permission to install a semi-permanent garden area.
  • You have access to rich soil to fill your beds and give your vegetables the best possible start.

Two important things you need to keep in mind when building raised beds on hard surfaces are drainage and staining.

Dealing with drainage

To ensure your raised bed won’t get waterlogged once installed, perform a simple test. Pour some water on your concrete or paved surface and see where it drains. Usually this will be toward the property perimeter or away from structures, but it’s important to mark this now to prevent future problems.

Once that’s completed, install your bed on the ground and set a level on top of one of the long sides. Have a few small blocks or wedges ready, then lift the end needed to bring the bed to perfect level, and slip a wedge under to block it in place. Be sure the bed is level both lengthwise and widthwise. Now you can slide a few small blocks beneath the boards where needed for permanent installation.

Preventing stains

Once you’ve installed your raised garden bed, monitor the surrounding area for leakage. There should be little to no runoff coming from beneath during regular gardening, but runoff can happen if the bed is left under a sprinkler or during heavy rains.

Any water that does run off from under the bed will be brown and will eventually stain the concrete. To avoid this:

  • Don’t overwater.
  • Cover the beds in winter.
  • Ensure the soil has adequate organic matter and nutrients to maximize absorption.

If runoff does occur, spray the soiled area with the hose to dilute and disperse it.

What about raised bed liners?

If you want to prevent leakage onto surrounding areas, you can include a raised bed liner when constructing your beds. However, ensure your soil has enough organic matter to absorb excess moisture or it might end up waterlogged.

Alternatively, you can use drainage material at the bottom of your bed. The Royal Horticultural Society recommends laying at least three inches of coarse gravel or stones covered with a geotextile membrane beneath a raised bed built over concrete or pavement. The membrane prevents the drainage material from clogging and getting mixed up with your soil.

What about soil depth?

When building raised garden beds on top of hard surfaces, ensure a depth of at least 18 inches. Salad and herb gardens can be grown in 12″ beds, but the deeper beds are better suited for a broad range of vegetable crops. Since plant roots will not have the luxury of reaching soil beneath ground level, you’ll need this depth to ensure healthy plant roots and to reduce watering needs. For more information, see our article about soil depth requirements for raised beds.

Things to keep in mind when installing raised beds on concrete or pavement:

raised beds on pavement

  • Concrete is alkaline. Over time, this may affect the soil in your raised beds. Test periodically with pH meter and adjust as required.
  • Raised beds built on dark pavement will usually have higher moisture needs than those built on a lawn or natural substrate. Keep this in mind when considering watering frequency.
  • Hard surfaces will prevent beneficial creatures like earthworms from entering raised garden beds from below. Thankfully there are other ways to bring worms into your garden. Dose your soil with regular additions of healthy, living compost and other “live” amendments such as manure. Not only will these amendments improve your soil health, they will also add beneficial creatures to the mix.

Patio Containers and Planters

If your space is too small to accommodate raised garden beds, patio planters and other gardening containers are an excellent way to cultivate edibles in small spaces. Patio planters usually have slatted bottoms to help with drainage.
Potted plants
Containers come in all shapes and sizes and may be easily relocated if conditions aren’t ideal. They can usually be moved to a covered area for winter months, though they will have a more limited capacity for growing crops when compared to raised beds and larger planters.

Are planters and patio containers right for you?

Planters and containers are right for you if you:

  • Are trying to grow food in a small space.
  • Aren’t able to install a semi-permanent structure like a raised bed.
  • Want to be able to move your plants inside during the winter or to different locations during the growing season.
  • Have access to nutrient-rich potting mix to fill your planters and pots.
  • Are working on a limited budget or want to start small, adding a few containers or planters at a time.

What type of container or planter is best?

There are a lot of options when it comes to container or patio gardening. Here is a comparison chart to help you get started.

Container MaterialChallenges and Benefits
Plastic• Lightweight.
• Breaks down quickly when exposed to sunlight.
• Darker colors absorb heat when sitting in the sun, so may dry out frequently.
• Is inexpensive and widely available.
• Has a high environmental impact.
Terra cotta• Absorbs water, so has a tendency to dry out soil quickly. (You can prevent this by lining with a plastic pot).
• May crack if soil is left in pots over the winter.
• Is particularly beautiful and can be decorative.
• Size is often limited. Larger pots are heavy to lift and awkward to move.
Wood• Natural material that may weather over time.
• Comes in a variety of shapes and sizes, or can be built to suit.
• Low impact to environment, but often higher consumer cost.
Upcycled containers• May need drainage holes added.
• Come in all shapes and sizes.
• Make great use of old items.
• Can often be free.

Locating your planters

Before purchasing your plants (or planting your seeds), mark out areas of sun and shade in your yard, patio, or balcony, and place containers accordingly. If you’re unsure how to do this, consider using a sun calculator. Balconies and other covered areas will only be suitable for growing most vegetables if you get full sun for at least six hours per day. On the other hand, lettuces will grow in dappled light, so these plants are excellent candidates for containers or planters located in semi-shade.

Feeding and watering

Planters and containers will need more regular fertilization than raised beds, since your plants are working with less soil and a smaller space to search for nutrients. If possible, add manure tea to your weekly watering schedule and watch your plants thrive.

VegTrug Raised Garden Planter

Soil mixes for patio containers and planters

Garden soil is often too heavy for container growing and plants usually do better with a lighter, more porous soil mix. Purchase potting soil at your local garden center, or add porous material like pumice to your containers. Pumice conditions and aerates the soil when mixed in. It also improves drainage. If planting into a pot without drainage holes, you can also add a layer of pumice to the bottom of the pot to provide air circulation and drainage. Coconut coir is another useful amendment for container gardening. It conserves water, improves soil structure, and helps plants retain nutrients. Alternatively, add an inch of coarse gravel to the bottom of your planters and pots. For more information about building soil for patio containers, raised beds, and planters, please read our full article.

You can also place spacers or small rocks beneath your containers to improve drainage. Even if the containers have holes, pavement or concrete may prevent the water from leaking out. Good drainage will keep your soil aerobic and well aerated.

Getting the most from your space

VegTrug Herb Raised Garden Planter
In general, you can plant containers and planters more densely than regular garden beds because there are more nutrients in potting soil mixes. Plants also aren’t likely to get as big in containers or smaller planter boxes.

To get the most from your space, mix quick-growing plants like lettuce, arugula, or radishes with longer growing plants like tomatoes (space-saving varieties like “Patio,” “Sugary,” or “Tumbler” are excellent choices). The quick growers will provide a lush and bountiful carpet beneath the slow growers, keeping out weeds and occupying the top layer of soil with their shallow roots.

You can also mix climbers (like pole beans, indeterminate tomatoes, peas, or cucumbers) with low growing plants or root crops like beets. The climbers will reach for the sun, leaving ample square footage for plants to occupy the lowest story.

Ideal vegetables for container and planter gardening

While almost any plant will grow in a container, some are easier to grow than others. Here are a few of our favorites.

LettuceWorks well in large, shallow containers, such as a window box or raised garden planter. Great for those semi-shade areas protected from the heat of summer.
CarrotsEnsure containers are at least 12 inches deep. Rolling patio planters work well for carrots.
CucumbersPlant in a container no smaller than 1 gallon. Include a stake or trellis for vines.
TomatoesUse a 5-gallon pot or bushel basket. Choose determinate varieties for a contained plant, or try indeterminate varieties if pruning and trellising are possible.
HerbsBasil, thyme, oregano, chives, rosemary, and sage all adapt well to container growing. Vigorous spreaders like mint do well in pots, which can help contain their growth.
SquashChoose space-saving or bush varieties and plant into a 5-gallon pot or larger.
StrawberriesChoose everbearing or day-neutral varieties to ensure a full season harvest. Strawberries are perennial, so be sure to store in a sheltered location over the winter. Refresh the soil in subsequent years with new potting mix, and prune where necessary to ensure the best harvest possible.
PeppersEnsure plants receive at least eight hours of full sun. Plant smaller varieties in a 2-gallon pot. Larger varieties will need a 5- or 10-gallon pot.
BeansPlant bush beans in planters or pots with full sun. Pole beans are good container companions for shorter plants providing trellises or stakes train the vines up and away.

Vive la Revolution!

While not everyone has a patch of soil at the ready, almost anyone can grow in planters, patio containers, or raised garden beds. With a few adjustments and a lot of passion, gardeners are converting concrete and pavement into productive garden space, one square foot at a time. Will you join in?

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Gardening On Concrete With Raised Beds and Patio Containers

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