|
What is a Raised Garden Bed?
- Raised
beds are garden structures are like very large containers without
bottoms.
- They
usually form a permanent element in the garden. Because they contain
such large volumes of soil, raised beds can be used to grow a wider
variety of deeper rooted plants, ranging from perennials, to shrubs
& even trees. Additionally, raised beds dry out less quickly than
containers. The beauty of a raised bed is that instead of plants being
at ground level, they are brought up to within easy reach, increasing opportunities
for gardening.
- Raised
beds are found in gardens everywhere because they are pleasing & ornamental
in themselves. Raised beds are wonderful way to break up space in any garden.
Raised beds provide focal points in design, & can be used to give
privacy, shelter & shade.
- For urban
dwellers with tiny courtyards, raised beds may be the only way to
garden at all.
- Raised
beds provide a fantastic solution to sloping garden sites, and sites
with poor or shallow soil.
- Raised
beds allow particular plants (e.g. trailing plants) to be shown to
advantage.
Location of the raised
bed
There are several
factors to consider when deciding where to locate a raised bed.
- Ensure
that the raised bed has access to water.
- Ensure the
raised bed can be safely accessed. Paths and abutting ground surfaces should
be smooth, non-slip, provide good traction, and be non-reflective. Be
sure to provide sufficient space to access the bed. Ensure ramps
should be appropriately shallow; provide handrails where needed.
- Consider
positioning the raised bed near other living & working areas.
Provide seating nearby (or incorporate recessed seating in the raised
bed design), or position the raised bed near pergola posts which can
be leaned against.
- Decide
whether privacy is desirable when positioning the raised bed e.g.
locate the raised bed away from main thoroughfares if appropriate. In
other situations, locate the raised bed near seating to encourage
social interaction.
- Consider
whether you would like the raised bed to be visible from indoors,
& locate the bed with this in mind.
- Ensure
that gardeners who work at the raised bed can be shaded from summer
sun, & sheltered from wind.
Design of the raised
bed
The shape, height &
location of the raised bed will depend on several factors.
- Who &
how many people will use the raised bed?
- What types plants will be grown? (e.g. ornamentals, fruit &
vegetables)
- Raised
beds can be almost any shape or height. Decide which is most suitable
for the gardeners’ needs and abilities and the site’s
characteristics.
- Design the
raised bed height according to the needs of the user:
- Will
gardening be done from a seated or standing position? By a gardener
facing the bed, or sideways to it?
- Incorporate
several heights in the raised bed, to cater for different needs and to
show a tiered effect of plants.
- Raised
beds can be built into sloping ground & be accessible from one
side.
- Alternatively,
raised beds can be free-standing & accessible from both sides.
As a guide to raised bed
dimensions:
- 450mm
height is a suitable height low wall for sitting –perched on the
side of the bed itself
- 600-650mm
is a good height for occasional rests & for people gardening from
a wheel-chair
- 700mm is a
medium height, accessible from a wheelchair
- 850 mm
height (a tall raised bed or planter box height) is ideal for
gardeners who have difficulty bending.
The width of the raised
bed also depends on the gardener’s abilities. Always ensure that all parts
of the bed are within easy reach, taking available tools into account.
Some people are more
comfortable working at relatively low beds, sitting down, or in a wheel
chair.
Others prefer to work at
elbow level, standing or leaning against the bed. All gardening in the
raised bed should be possible without straining to reach up or down.
A raised bed that is
accessible from both sides can be twice the width of a bed accessible from
one side only.
- 600-750mm
width is suitable for a raised bed accessible on only one side.
- 1200mm
width if the raised bed is free standing & accessible from both
sides.
Design features
- Raised
beds can be any almost any shape, not be rectangles or squares. For
example, raised beds can be curved, L, U or T
shaped providing beautiful solutions to delineating different spaces
in a garden.
- A recessed
seat can be incorporated in the wall of the raised bed.
- A wide
stretch of wall coping can be included in the raised bed design for
leaning against comfortably.
- Other
design considerations include handrails.
- The actual
width of raised bed wall & coping is also important - the narrower
the edge, the closer you can get to soil & plants.
Construction
Raised beds usually rest
on the ground (e.g. a gap is left in the paving to allow construction of
the bed, so that the base of the bed can drain directly into the ground).
In some cases a raised bed will be constructed directly on top of a paved
surface. In that case it is necessary to incorporate weep holes in the bed
walls, to allow drainage of water.
Raised beds can be built
from a variety of materials, including treated timber (ensure it is non-toxic
if you are growing food crops), stone, concrete, brick, and modular brick
units. Modular Raised bed kits are also available. Seek professional advice
about appropriate materials & construction methods, but also ensure the
construction material you choose is aesthetically safe, pleasing, &
that it is in harmony with surrounds.
Raised beds that need to
be moved (e.g. in winter) should be small & light enough to carry,
fitted with handles, or on wheels or castors.
Raised beds can be very
heavy when filled with soil and may be inappropriate for roof gardens,
decks or balconies.
Soil for raised beds
Raised beds should be
filled with a good quality soil, appropriate to the situation. Where weight
is a concern, opt for a light weight growing medium.
The soil depth in the
raised bed depends on raised bed height & plant requirements.
Mix moisture crystals in
the soil to retain soil moisture. Cover exposed soil surface with mulch
(e.g. leaf litter), &/or grow groundcover plants.
Plants for raised beds
Many plants are suitable
for raised beds (small ornamental trees, shrubs, vegetable, fruiting plants,
herbs, grasses, trailing plants). The main limiting factor is soil depth
required for the plant root system. Choose plants whose needs for
sun/shade, soil depth & moisture requirements, match that provided by
the raised bed. The walls of high raised beds can be beautifully softened
with trailing plants.
Table Planters
One disadvantage of
conventional raised beds is that they lack space underneath for the knees
& feet of gardeners. It is possible to build raised beds with sides
that slope outwards from the base, allowing foot space. An alternative is
the table planter, really a type of raised bed. This consists of a shallow soil-filled
tray supported on legs. The advantage of the table planter is that it
provides leg clearance for gardeners using wheelchairs. The table height
can be customised.
The soil depth should be a
minimum of 120 mm.
Select plants suitable for
the soil depth and sun/shade conditions. Plants that prefer well-drained
soil, tolerating low soil moisture are an excellent choice. Trailing plants
look wonderful cascading over
the edge of the planter.
Since the shallow container dries out quickly in full sun, mulch the soil
and add water crystals to the soil to minimise dehydration. Frequent
watering, or a drip watering system
is required.
The width of the table
should not exceed what can be reached. A free standing table accessible on both
sides, should be no wider than about 1200mm. If
the table is accessible on one side only, then
its width should not exceed
around 600mm.
|
