Category: Containers

Raised bed gardening offers several advantages over normal ground-level gardens.
It also offers several disadvantages that have to be taken into account in the planning.

Raised Beds

To begin with however, raised bed gardening means you build an enclosure and fill this enclosure with soil.
You can make the enclosure as high as you desire.
Remember that if you build the walls high enough for wheel chair access, those walls will be holding back an immense weight of soil and will have to be built strongly enough to handle that pressure.

Advantages

Raised bed gardening advantages include:
The ability to eliminate stooping over to weed and work with the plants. For those with the inability to kneel or bend over, raised beds are well worth considering.
Raised beds allow the gardener to escape their natural soil limitations and create a super-soil in the enclosed space that will grow anything. An enclosure is treated as if it were a container instead of a garden soil. A raised bed is simply a giant container garden,  and it follows almost the same container gardening rules

Soils

Soils in slightly raised containers, only a few inches over the soil level, can easily be filled with garden soil. However, the taller the garden and the more intensive the gardening, the more there is a need for an artificial soil.
Raised beds warm up earlier in the spring and vegetables can get a head-start when grown in a raised bed.

Watering Problems with Raised Beds

Having said all that, it is important to note the following:
Raised beds demand more water than in-ground beds. Water drains from them faster and success depends on watering more often than for in-ground flower beds.
Because of the increased watering needs, extra compost or organic fertilizer is required (the extra water takes away more water-soluble Nitrogen) than with in-ground beds. Again, this is a feature of container growing.

Perennial Threat

Perennial plants in raised beds are more susceptible to winter damage because their roots are above the soil line. Tender plants should not be grown in raised beds in colder areas. This unfortunately means that those gardeners who want to use raised beds to substitute for heavy clay soils will have trouble growing tender plants in those beds. The solution is to grow hardy plants there.

Construction

Construction of raised beds has traditionally been accomplished by building a rectangular enclosure of the desired size. I’ve made them from concrete building blocks (and then planted the holes as well as the enclosure) as well as railroad ties, cedar logs, and laid stone.
This however doesn’t mean they have to be square – a contained bed can be any shape you want. One important consideration is width.
One has to be able to reach from side to side in raised bed gardening. There is little point in having a no-man’s land in the middle of the bed that nobody can reach. Access from both sides means the bed can be wider than if access is only available from one side.

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Raised bed gardening resources – from kits to supplies
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The author’s raised beds for his newly planted shade cottage garden
Raised garden design concepts fall into several different categories.

I apologize for the lack of images here – we’ve had server issues and I’m rebuilding all posts. Make a comment and jog my memory that I missed this one

Tall Raised Garden Design

The first is in gardening for the disabled where the beds have to be constructed tall enough to be wheelchair accessible or tall enough to eliminate stooping over (this is a great idea even for those of us with good backs) 🙂

Soil Depth

The second is for reasons of soil depth. In gardens where adequate soil is not available, then raised bed gardening allows plant roots to thrive. This is why we’re building a great many beds like this, our soil is 2-inches of clay over shale rock. Kinda tough to garden on…

Esthetics

The third raised garden design concept would be for esthetic reasons; to fit into the concept of design that allows for differing heights. Think different heights of plants in the same way as we have different heights of furniture in a room. Smaller plants can be shown to greater advantage in taller beds; in fact, we often see specialist alpine flowers in raised bed gardening or taller containers so their diminutive stature doesn’t take away from their beauty (and frankly so the regular garden weeds don’t eat them for lunch).
Note that there are common horticultural concerns in all three design reasons. See below.

Why Raised Garden Beds

In thinking of raised garden design then, the question has to be for what purpose you’re raising the beds.

For The Physically Challenged

The beds have to be far enough apart to allow easy access for wheelchairs or wide garden carts.
The pathways between the beds have to be firmed and not muddy. Getting bogged down or having to work hard to move a device along a muddy path is not good raised garden design.
The beds have to be constructed in such a way to allow the proper height and the proper reach to the beds. There’s little point in having a bed too low or too wide if the gardener can not reach all parts of the raised bed to work it.

For Soil Depth

If the raised garden design is for increasing soil depths, then beds can be closer together but the crop being grown has to be considered.
Annuals do well in 8 inches of soil so one tier of railroad ties (or similar depth) is adequate for a great crop of annual flowers or vegetables. The width of the bed is up to the gardener and what they can comfortably reach.
Perennials or woody plants will require a different thinking. It is not the soil depth that will kill off perennials or shrubby plants. Most of these plants will be fine with 12 inches of soil.

Winter Damage Is Worse For Perennial Flowers

Depending on the winter temperatures, it is more likely perennial plants and shrubs will be damaged or killed in raised beds than in the ground. Plant roots of commonly grown shrubs and perennials tend to die off when the soil temperatures reach -5F. (there are exceptions)
In smaller raised beds or shallow beds over rock, the soil freezes from the top and the bottom and comes closer to reaching air temperatures than does deep soil. If your air temperature goes below the -5F and so does your soil, then you’re going to start losing plants.
The larger the raised bed, the more it acts like a regular ground-level garden
Deep soil has a flywheel effect where the deeper soils that remain unfrozen act as thermal buffers to cold penetrating deeply or for the actual soil temperature to drop too far below freezing.

How Big Do We Have To Build?

Our need then is to create wide beds and deep enough beds so we create our own thermal flywheel and only grow plants such as Iris and Hemerocallis that are tough enough to handle extremes of soil temperatures. More tender plants such as Lavender will not survive these temperatures.
Raised bed design for deep survival calls for beds to be at least 18 inches deep and likely 6 feet wide. These sizes would be variable depending on which zone (colder = deeper and wider) and which plants the gardener wishes to grow. The tougher plants can go to the edges while the more tender plants should be planted in the center.
But it all depends on the lowest winter temperature you get. Colder equals bigger beds needed.

Watering Issues

Note that taller raised garden design means that we’ll have watering problems as gravity will pull available water downwards. You will have to water more frequently and deeply to overwinter plants in such raised beds.
Thaws during the winter will also cause the soil to lose moisture and this can cause as much damage as summer droughts to some plants.

Esthetic Design

Raised garden design for esthetic reasons is the easiest of the reasons for creating these garden beds. This is simply a matter of constructing the beds to the appropriate depth and growing in them. Note that watering will still be an issue.

Another Challenge

Another horticultural challenge is the actual soil to be used. Raised beds share the properties of container gardening and soil structure. Because you have to water more frequently, there is a serious danger of compacting the soil in raised beds that does not exist to the same degree in garden soil. (Water weighs approximately 10 pounds to the gallon so if you thump several gallons on directly with a hose, you’re mashing down the soil with weight.)
Raised beds will require the addition of extra amounts of organic matter to loosen up the soils and prevent compaction. This is easily done with shallow beds for vegetables and annual flowers. Merely dig in peat moss and compost at the ratio of 1 shovel of peat, 1 shovel of compost/manure for every 3 shovels of soil that is turned over in the annual spring or fall digging.
This is more of a problem for perennial beds and tall permanent beds that can not be dug every spring. In these I’d recommend you invest in drip irrigation so now hand watering need be done. I’d also recommend you add extra compost/organic matter every year so the earthworms stay happy and do your digging/aeration for you.
So the last aspect of raised garden design then falls into the category of shapes and structure. And here you’re on your own to create your own garden fantasy. Remember that wood timbers lend themselves to square classic shapes while bricks and pavers can be used in squares or round edge beds.
But no matter the shape, the growing considerations above have to be your initial concerns.  You can get more tips on raised beds and container gardening ideas right here

Shopping Resources for this Page

Raised garden design options  and available to fit many garden systems