Choosing the right plants
Plant material is one of the key elements to consider on a landscape construction site. Vegetation is essential in protecting and enhancing the biodiversity and landscape character of an area. It is a living, dynamic element that provides many benefits to
the site.
Functionally, plant material creates habitat for local animals and birds and can modify exposure to sun and wind, define space, direct movement and stabilise slopes. Aesthetically, it provides visual interest through a variety of colours, textures and forms.
Step 1: Site analysis
Early in the design phase of a job, the existing site conditions and level of maintenance available after construction must be carefully considered. A thorough understanding of these can maximise the success of the vegetation on the site.
A site analysis asks a series of questions regarding the existing site conditions.
It highlights areas which can be seen as opportunities, and minimises those seen as constraints. It provides an excellent tool to address the following site issues:
Existing plant material
- What are the heights, spreads and conditions of existing specimens?
- What are their habitat values?
- Should they be retained or removed?
- Is it native or exotic to the area?
- Are there heritage or Tree Preservation Orders on particular specimens?
- Is any of the existing plant material on the local council's weed list?
- Will it be in close proximity to future construction works?
- Will it require protection during the construction phase?
- Is local bushland nearby?
Soils
- What are the soil characteristics for the site?
- How stable are the soils?
- Are they prone to erosion?
- Do the soils have a fine component which will be difficult to remove from polluted stormwater?
- What plants are best suited to the soil types on the site?
Topography/slope
- Are there steep slopes which require stabilizing?
- Are there poorly drained flat areas?
Micro climate: aspect
- Which direction does the site face? North and west facing aspects are drier, while south facing ones are moist.
- Is there overshadowing from buildings or existing vegetation?
Micro climate: wind direction and frequency
- Should these be encouraged or screened?
- Are there any salt-laden winds?
Micro climate: annual rainfall
Should plant material be selected to suit existing moisture levels, or is additional irrigation required?
Views
Consider the views both into and out of the site. Depending on their quality, these should either be encouraged or screened.
Step 2: Choosing the right plants
After the site conditions are well documented, the selection of plant material must suit these conditions.
Along with other design considerations, when you're choosing plants you should aim to:
Protect soil health
Reduce the use of imported soils or composts, which may contain weed seeds and other pathogens. - Reduce the modification of existing site soils with fertilisers. These often wash off site, polluting local watercourses. Instead, add (appropriately certified) composted organic matter to improve the existing soil.
- Preserve existing local seed banks in the existing soil.
Minimise water use
- Reduce future irrigation requirements. Select species which are `water wise'. The application of mulch can further reduce water requirements. Use drip irrigation if further moisture is required.
- Reduce the amount of lawn areas, as these require very high maintenance. These could be replaced with ground covers or native grasses.
Minimise need for chemical pest control
- Reduce the need for chemical control of insect attack and fungal diseases by selecting a diversity of local species, which do not have inherent health problems, and by maximising the health of other species
Protect the integrity of local bushland
- If the site is near bushland, reduce the risk of fire with fuel-free zones and fire retardant species.
- Don't select potential weed species.
- Protect and enhance local species by retaining and replenishing the canopy trees and understorey planting for habitat. Choose local native vegetation wherever possible.
Other design considerations
- Provide a human scale–think about how people will use the site.
- Consider whether shading of neighbouring properties would reduce their solar access.
Satisfying these requirements will lead to planting designs which will enhance the biodiversity of the site and protect environmental resources. Landscapes which have followed the above suggestions should require less maintenance, be more self-sustaining and attract native animals.
More information
- Your local council, for policies on:
- weed management
- landscape management
- significant and heritage
- trees register
- fire prone areas and fire management
- habitat protection
- tree protection
- Tree Preservation Orders
- Local nurseries
- Local bush regeneration groups
- Flora for Fauna - (Nursery and Garden Industry Australia and National HeritageTrust)