Raised bed gardening

Raised-bed gardening is a form of gardening in which the soil is formed in three to four foot wide beds, which can be of any length or shape. The soil is raised above the surrounding soil (approximately six inches to waist-high), and is enclosed by a frame generally made of wood, rock, or concrete blocks, and may be enriched with compost. The vegetable plants are spaced in geometric patterns, much closer together than in conventional row gardening. The spacing is such that when the vegetables are fully grown, their leaves just barely touch each other, creating a microclimate in which weed growth is suppressed and moisture is conserved.

Raised beds produce a variety of benefits: they extend the planting season, they can reduce weeds if designed and planted properly, and they reduce the need to use poor native soil. Since the gardener does not walk on the raised beds, the soil is not compacted and the roots have an easier time growing. The close plant spacing and the use of compost generally result in higher yields with raised beds in comparison to conventional row gardening. Waist-high raised beds enable the elderly and physically disabled to grow vegetables without having to bend over to tend them.

Raised beds lend themselves to the development of complex agriculture systems that utilize many of the principles and methods of permaculture. They can be used effectively to control erosion and recycle and conserve water and nutrients by building them along contour lines on slopes. This also makes more space available for intensive crop production.  This form of gardening is compatible with square foot gardening and companion planting.

Raised beds range in height, starting at about 6″. In general, the more soil depth that’s available to your plants, the more freely their roots will grow. More soil also holds more moisture, so a deeper raised bed will require less frequent watering. It is possible to install a raised bed on poor or compacted soil, or even on concrete. If this is the situation you have, buy the deepest bed you can afford. A depth of 10-12″ is preferable. Keep in mind that the deeper the bed, the more soil you’ll need to fill it.

Materials and construction

If using timber to raise the garden bed, ensure that it is an untreated hardwood to prevent the risk of chemicals leaching into the soil. A common approach is to use timber sleepers joined with steel rods to hold them together. Another approach is to use concrete blocks, although less aesthetically pleasing, they are inexpensive to source and easy to use. On the market are also prefab raised garden bed solutions which are made from long lasting polyethylene that is UV stabilized and food grade so it will not leach undesirable chemicals into the soil or deteriorate in the elements. A double skinned wall provides an air pocket of insulation that minimizes the temperature fluctuations and drying out of the soil in the garden bed. Sometimes raised bed gardens are covered with clear plastic to protect the crops from wind and strong rains. Pre-manufactured raised bed gardening boxes are now available. There are variants of wood, metal, stone and plastic. Each material type has advantages and disadvantages.

Location and Set-up

For optimum plant health and productivity, most vegetables should receive at least eight hours of full sun each day. The more sun, the better, so it makes sense to locate your garden in the sunniest part of your yard. Avoid low, wet areas where the soil could stay soggy. Because your garden will need to be watered during the growing season, you’ll want to have relatively easy access to a hose.

Good soil is the single most important ingredient for a good garden. Raised beds give you an immediate advantage over a regular garden, because when you fill your raised bed, you can fill it with a blend of soil that’s superior to the native soil in your yard. Soil that’s loose and rich with nutrients and organic matter will allow the roots of your plants to grow freely, and ensure that they have access to the water and nutrients they need to sustain healthy growth.

Before placing your raised beds in their permanent location, be sure to remove grass or perennial weeds from the area. Use a garden fork or shovel to loosen the native soil to a depth of 6-10″. This will improve drainage and moisture retention in the raised beds. It also means that even with a 5″-high raised bed, your plants will think they’re growing in a bed that’s 12-18″ deep — plenty of room for carrots, potatoes, full-size tomato plants and most any other vegetable you’d ever want to grow. If you’ll be filling more than one raised bed, you might want to buy your soil in bulk — by the cubic foot or cubic yard. For most situations, we recommend these proportions:

• 60% topsoil
• 30% compost
• 10% Potting soil (a soilless growing mix that contains peat moss, perlite and/or vermiculite)

If you do not have access to quality topsoil, an acceptable substitute would be a 50-50 blend of soilless growing medium, called potting soil and compost. If you want to add peat moss to the bed, it should not be more than 20 percent of the total mix. Peat moss is naturally acidic and is not a good medium for growing vegetables.

Tending Your Garden

Planting intensively keeps weeds to a minimum. Early on you may need to weed a little every week, but by mid growth your weeding chores should be over. When weeds do crop up, you’ll want to remove them quickly so your vegetable plants aren’t competing for moisture, nutrients and root space.

The soil in a raised bed doesn’t dry out as fast as it does in a regular garden. The sides of the bed help retain moisture and the plants shade the soil to reduce evaporation. Once plants are well-established, your watering chores should be minimal except in hot weather and periods of drought.

Crops that grow take three or four months to mature usually benefit from a second, midseason application of fertilizer. Almost all vegetables appreciate a monthly dose of water-soluble fertilizer, especially one that includes humic acid, seaweed and fish emulsion. These water-soluble nutrients are immediately absorbed by plants and help keep them healthy in periods of stress. This is an easy way to minimize pest and disease problems.

You can begin harvesting food from your garden just as soon as it looks ready to eat. Crops are usually tastiest and most nutritious at or just before their peak of ripeness. Remove any spent fruit or foliage, as well as any damaged or diseased plant material. Keep an eye out for pests and address any issues promptly. Some plants, including pole beans and most tomatoes, need a cage, trellis or another type of support to grow properly and produce a good crop. Plant supports also save space, help keep the garden neat and make it easier to access plants for harvesting.

Watering

Different types of soil have different abilities to hold water. A clay-based soil holds onto water because each little particle of clay has lots of surface area for the water to grab onto. Sandy soil, with its bigger particles, lets water pass through quickly. A good loamy soil retains some moisture, yet is also well-drained.

Adding compost to the soil improves its ability to supply your plants with just the right amount of water. Think of sandy soil like a wire basket full of golf balls: turn the hose on and the water runs right through. Adding compost is like adding sponges — water still runs through, but some is stored in the sponges. Compost also helps improve clay soils by aerating them and providing better drainage. Plants absorb oxygen through their roots and can drown if the soil stays soggy for weeks at a time. Raised beds and compost can help prevent this from happening.

The best way to monitor soil moisture is with your hands. When you stick a finger down into the soil, it should feel lightly damp – like a sponge that has been wrung out. Don’t just feel the surface; get your fingers down to the root zone (3″ deep or so) at least once a week. In hot weather, plants may wilt during the heat of the day. This isn’t always an indication that they’re moisture-deprived. In many cases it’s simply a way for the plant to reduce moisture loss through its leaves. Checking the soil tells the real story.

Planting intensively in a raised bed garden minimizes moisture loss. Plants shade the soil surface and help protect one another from the wind. Mulching around plants with 2-3″ of shredded leaves or straw is another effective way to retain moisture and add organic matter to the soil. To keep your plants healthy and productive, don’t let the soil dry out completely. If delicate root hairs die back, the plant must direct its energy to re-growing them, rather than to producing fruit. Water-stressed plants can also become bitter and tough.

Steps to Take to Prepare for Raised Bed Gardening
a. Test your soil before you start planting.  Start with a planting mix and then add the appropriate compost to convert the soil so it holds nutrients, water, and oxygen for prosperous plants.
b. Don’t walk on the soil. One of the advantages of growing in raised garden beds is the fluffy soil. Make sure you are able to reach every inch of your raised garden bed from the outside.
c. Mulch. Use wood chips, straw, grass, or leaves so you have to do less weeding in the long run. Mulching also helps to keep the soil in your raised garden beds moist.
d. Use worms for optimal growth. They break down raw organic matter, digesting the soil and aerating it to relieve compaction. They also add nutrients via their digestive systems.
e. When planting veggies, keep companion planting in mind. Some plants get along and some do not. For instance, corn grows well in the same bed as cucumbers, but not in the same bed as tomatoes. And onions thrive when planted in the same garden bed as lettuce and carrots, but are hindered when planted with beans and peas.
f. Compost. Use a method such as trench composting to feed your raised garden beds your kitchen and garden waste. The plant will take the nutrients it needs right at the root.

How to plant a raised garden bed:

1. Add quality soil and/or compost. Then use a rake to level it off so the surface is smooth. Make sure to remove any rocks, large sticks, and other debris.
2. Plant your plants a little closer together than you do in your other beds since the fertilizer and manure is more concentrated in the smaller area.
3. Plant taller plants such as tomato plants on the north side of the raised garden bed.
4. Next, plant medium-sized plants such as peppers in the mid-section of the bed.
5. Short plants like radishes, carrots, and beets should go in the front.
6. Plant onions and herbs along the outside of the bed and the corners to save space. These plants will help to ward off insects.
7. Generously water your new raised garden bed immediately after you are finished planting

Raised Bed Liners Contain the Mess

Liners let you install raised beds on any hard surface. They let the water drain, but holds soil and prevents it from washing out. It also makes the raised bed more durable and prevents toxic materials from leaching into the soil. For lining, use landscape fabric found at garden supply stores or cloth fabric from clothing. Avoid non-porous plastic, as it can retain too much water and discourage beneficial insects and worms.

Composite Wood Plastic beds

Composite ‘timbers’ are made of a blend of wood fiber and UV-protected recycled polypropylene. They have a wood grain texture and earth brown color. They are designed to be used with flanged corner joints which can be stacked to make the bed any height in increments of 6”. Composite Raised Beds give you the look of wood, but the durability of composite materials. Combining wood fibers with plastics means the beds are lightweight and easy to maintain and could also outlast many of the wooden beds on the market.

The composite timbers are very light. They are hollow boards with a central stiffener. These boards are very easy to lift and assemble. Because the composite ‘timbers’ are lightweight, and since screws are used to attach the timbers to the anchor/stacking joints, these beds are easy to disassemble and reassemble without damaging the materials. If you move to a new home, you can bring your raised beds too. They have a wood grain imprint, and at a casual glance give the appearance of solid wood. But unlike natural wood, there is no variation is color or texture and there are no knots. They are weather resistant and washable. Even more advantageous is the fact that they can be re configured or expanded.