Sweet Viburnum: Guidelines For Garden Bed Construction

Since you're likely to plant your sweet viburnum in a garden, you must be aware of the requisite guidelines for constructing a suitable bed. This is especially so if implementing it on city land or a newly developed residential subdivision. Such garden designs must conform to official standards.

A good example of garden bed construction guidelines is presented in the City of Ballarat's Landscape Design Manual (LDM).

City Of Ballarat LDM: Garden Bed Construction Guidelines

Firstly, the minimum garden bed excavation is 300mm. Remember to stockpile the site soil, which is recommended for use in your construction, instead of importing soil. The sub grade layer in the planting area should be ripped to at least 150 mm in depth. This layer should also be cultivated with gypsum using a rate of 2.5 kg/ m2.

There are two separate sets of requirements regarding existing and imported soils to be used in the garden:

The requirements for existing soil include:

- It's derived from the top 100 mm layer of site soil.

- It must not have perennial weeds or their bulbs, roots or rhizomes.

- No building rubble, concrete, bricks, plaster, oil, timber or any form of deleterious matter should be present.

- It must possess below 5% stone by dry weight, but such stones and rocks should not be greater than 5 mm in diameter.

- Possess a texture ranging from light to medium friable.

The requirements for imported soil include (based on the Australian Standard AS4419):

- Where imported soil is required, the subsoil should be ripped and cultivated to 300 mm in depth, in order to combine with the existing soil base.

- Just as with existing soil, imported soil should not have perennial weeds or their bulbs, roots or rhizomes.

- No deleterious matter should be present.

- Have a similar stone mass as existing soils.

- Possess a pH ranging from 6.0 to 7.0.

- Have a texture ranging from light to medium friable.

- No silt material should be present.

- The soils should not be hydrophobic.

- 100% of the soil mass should be able to pass through a minimum sieve size of 0.35 mm. This percentage reduces in the following pattern: 90-100%, 70-80%, 45-55%, 20-30%, 5-15%, and 3-5%; as the sieve size reduces in the following pattern: 1.18, 0.6, 0.3, 0.15, 0.075 and 0.002, respectively.

Once the existing or imported soil meets the specific requirements, it can then be placed on the subsoil, maintaining a minimum depth of 200 mm and a top level that is 100 mm below the paving. The subsoil, that was initially ripped and cultivated, is graded and compacted lightly in order to reestablish the final soil level that is not less than 300 mm below the paving level. Its compacting density should be about 70% of the modified dry density. A 75 mm deep layer of mulch is then placed at the very top of it all.

Finally, when excavating a hole in which to plant the sweet viburnum, ensure that it provides a clearance of 75mm to 100mm around the root ball. This hole should not be deeper than the root ball height. It should also be backfilled with approved topsoil.


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Keith Kelso enjoys planting a wide range of exotic and native plants. These plants can be sourced from Nursery Online. They stock a rich collection of plant varieties. Visit http://www.nurseryonline.com.au/viburnum-odoratissimum-sweet-viburnum-200mm/ for more information and advice on online plant purchases.