By Todd Layt
Raised or mounded gardens have an array of home garden benefits, as well as some wonderful garden design aspects. Lifting a garden above the general ground level often results in much healthier plants, and far less gardening problems.
Many Australian native plants really benefit from a raised garden, due to the virtual elimination of wet feet. Mounded gardens often result in reduced maintenance. But one of the greatest aspects of a raised garden, is the improvement in height contrast of various plants, and the exciting gardens that can be created using height as a major garden design tool.
Many of the most beautiful Australian and exotic plants do not like continuous wet feet. Often excessive irrigation, high periods of rainfall, poor mulching practices, and flooding can cause the top root zone area or the crown of a plant to become water logged.
This often results in problems such as Phytophthora or other fungal problems, particularly in the more humid areas such as NSW and Queensland. Just a slight rise of 75mm or more above ground level, can bring amazing benefits. Even plants that can cope with wet feet will still often look much healthier when grown in a slightly raised area, compared to a flat or depressed area.
By using slightly raised areas, the bad effects of these problems can be greatly reduced, as water more easily drains away from the growing point. If a mulch that has many fines is ever used (mulch that almost looks like a soil), a raised garden bed is almost essential, particularly in humid areas. Mulch that has only chunky pieces and no fine particles is of course, a better choice for flat, depressed and even raised areas.
In general, a raised or mounded garden is more forgiving, and can help eliminate many horticultural problems, particularly drainage problems.
Apart from healthier plants, raised gardens have many other benefits. A raised vegetable garden for example makes replanting and digging much easier on the back. I personally use a raised vegetable garden, and after growing in that for a few years, I would never go back to a garden at ground level. The truth is my wife does the vegie gardening, but you should see the great vegetables a raised garden can grow. Raised ornamental planter boxes allow for ease of weed control and pruning. Raised or mounded gardens make it slightly harder for weeds to invade. There is a reduced chance of weed seeds blowing in, and a much lower risk of weeds washing in, as well as the fact that even slightly raised gardens allow spade edges around lawns to be more easily maintained, particularly with easy to look after Buffalo turf. Highly maintained lawn areas are frequently irrigated, and this may be bad for the plants, so by rasing the garden, it allows the excess irrigation to run off. Raised beds are great for keeping unwanted pedestrians or vehicle traffic away from gardens. You often see around car parks or median strips on roads, that the areas are raised with a concrete border, which helps keep cars off. If gardens are raised higher, they are great at stoping people from walking on them. Raised gardens also help reduce erosion. Depressed or flat areas that are subject to high water flows can lose soil and mulch in times of heavy rain. Raised gardens are less likely to be subject to these water flows. Very tall raised gardens (earth embankments) are great at reducing noise, as the earth mounds act as a noise barrier. These taller gardens can also be wonderful viewing platforms, particularly if a path and viewing area are added. Finally, some raised gardens, or raised planter boxes can have other uses. They are not only beautiful gardens, but they can be benches (seats), viewing platforms, access ramps, pathways, roads, window features, portable displays, dividers and great entrance displays.
Nature is a wonderful inspiration for landscape design. The most inspiring natural landscapes generally have massive height variations, including vistas such as rolling hills, mountains, ocean cliffs or sand dunes. It should be no different for the home garden. Mounded gardens or structured raised gardens can change the line of sight of a landscape, helping to create interest, and often defining the landscape. Scenery of different heights adds a whole new dimension to the landscape, being far more interesting than a flat area. Raised gardens allow sloping sites to be tiered, providing a series of raised level areas. By changing the height of the base garden, it allows gardeners to use plants of similar height in a contour contrasting manor. For example, Cassa Blue (blue foliage) and Little Jess (green foliage) are similar height Dianella caerulea plants. By planting Little Jess on the lower part of the slope, and by planting Cassa Blue 40 to 60 cm up the slope, Cassa Blue will appear to be taller. On large mounded gardens, foliage plants such as Dianellas, Lomandra, Phormiums and Cordylines can be used to create a screen of foliage, which will look good all year round. Screen trees can be used at the top and back, to give even more height contrast. A similar technique can be used with flowering plants, but the maintenance of flowering displays is a lot higher.
Raised or mounded gardens help gardeners mimic nature. If inspiration is not reason enough to use raised gardens, then the horticultural and other benefits surely are. Next time you create a garden, or change the plants in your existing gardens, stand back, and picture in your mind, how height levels and raised gardens can be used to enhance your design.
Some of the best new plants for a raised garden. Easy to look after plants.
Phormiums (New Zealand Flax lilies)
- Sweet Mist
This is a very compact new bronze coloured Phormium, with amazing dense foliage. It only grows to about 30 to 40 cm high. An excellent plant for the bottom of the raised garden.
This is a newly released Phormium with vibrant bronze, redish, and orange toned foliage. It grows to about 50 to 60 cm in height. It really shines in sunlight. Not easy to find.
Dianellas (Australian Flax Lilies)
- Baby Bliss
A small blue foliage flax lily, with magnificent Spring flowers. Great for the lower parts of a raised garden.
- Emerald Arch
This Flax grows to 50 cm in height, with broad arching green foliage. Great for heavy shade or full sun.
- Cassa Blue
Amazing blue foliage, with incredible flowers and berries.
- Little Jess
A great ground cover flax. It grows to 40cm, but spreads and covers the ground. Deep purple flowers. Good for rock gardens.
- Little Rev
An architectural beautiful, low growing blue foliage flax, with upright leaves to around 30 to 40 cm.
Add a little purple and blue foliage to you raised garden. A tough, gorgeous Flax.