Landscape Softworks

Refer to:
HS610.01 / Open Spaces

PS610.02 / Open Spaces

• ​The educational value of nature areas and conservation areas in schools has been well recognised, but their establishment and maintenance has met with varying degrees of success. The establishment of School Environmental Areas (SEA) have been advocated under the DoE “Greening of Schools Program”, and packages (including DoE's "Hands on Learnscapes" CD) have been issued to schools to assist them in developing their own "Learnscapes". 
• Policy is to retain existing trees and tree stands, both native and exotic, plus the understorey native vegetation where practicable. Existing trees can usually be retained and maintained subject to their age, condition and effects of site development upon water supply, drainage, soil compaction and disturbances/partial removal of the root system generally. Assessment of trees to be retained should be undertaken in consultation with a suitably qualified Arborist in order to assess suitability for plant retention / removal.
• The ground survey data reliability /order of accuracy should be considered.  The relevant Australian Standard only guarantees contour accuracy to half a contour interval, although spot levels are considerably more accurate.  Where tree retention looks to be questionable, the situation must be reassessed early in the construction phase to eliminate the cost of tree removal when buildings are complete.
• Indigenous Australian species, particularly Eucalyptus spp., have evolved over time to survive inhospitable/hostile conditions.  Under stress, these trees will sometimes sacrifice a limb to ensure the survival of the whole tree.  As a result, retained mature trees may contain dangerous dead branches which can snap off in high winds: all retained vegetation should be inspected and reassessed and any necessary tree surgery carried out by an arborist/tree surgeon as part of the construction contract.
• Retention of understorey vegetation depends very much on the motivation and attitude of senior school staff.  Understorey vegetation, perhaps due to poor design integration, is sometimes seen as:
  • Providing secluded areas which are difficult to supervise
  • Acting as rubbish traps
  • Harbouring vermin
  • Being of a “poorer” quality than adjacent newly laid turf
  • Presenting a bush fire hazard

     It can however be:

• Used effectively to define spaces
• Attract native birdlife
• Provide instant maturity

• Areas of retained vegetation are more fragile than turfed areas and will not survive unrestricted access. Except where the understorey is extremely dense, nature/conservation areas only succeed when fenced off to control access. The effect of fencing is two-fold:
  • Restricted access enables the area to flourish, thereby maintaining or even improving its original quality and diversity; and
  • The delineation of the area gives it a special “cachet”, projecting the image that the school is the custodian of a valuable resource.
• Protect areas of retained vegetation during the construction period by fencing to eliminate compaction by construction plant, equipment and vehicles as well as the storage of materials within the tree root zone. Fencing should be placed beyond the drip line of trees
• Where an area is to be retained to represent the whole pre-existing plant community, it should also be fenced.

Turfing is the preferred technique for installation of grass because:

• Speed of establishment. The use of grassed external areas is essential for a school to function adequately; landscape softworks are usually installed just prior to occupation.
• To sprig or seed is impractical because of the length of time required to establish a useable grassed surface; except in relatively flat, low-use areas of a school site, not affected by last minute service installations or required for builders’ access, equipment, sheds or materials storage.
• The soil surface is vulnerable to weed invasion and erosion with all grassing techniques other than turfing. An on-going maintenance problem could be created.
• Seeding should never be considered when the specified species is Kikuyu. Grass produced from Kikuyu seed is more upright in form than is desirable for a dense turf sward; however Kikuyu seed may be included in seed mixes.
• Free Play Areas should be turfed rather than seeded, and existing rough grass should not be used unless inspected and recommended by a Landscape Technical Specialist.
• Consider the use of alternatives to turfing in non-play areas e.g. Woodland areas.
• Consider the use of synthetic grass in areas where the conditions are unsuitable for turfing.
• Turf Species Selection:
  • Kikuyu (Pennisetum clandestinum): has vigorous growth habit under most conditions but can also be a weed, which needs strong control. Suited to active areas.
  • Couch (several species): It requires suitable climate and soil conditions. It can also be a weed with fine pollens, which are a major source of allergens.
  • Buffalo (Soft Leaf Shademaster, Sir Walter, Palmetto, ST 85, ST 91, ST 26 Austine)- shade tolerant requiring less mowing than Couch or Kikuyu.
  • The Contractor or Turf Supplier is to provide Certification of grass type.
  • Commercial soil testing laboratories make it possible to specify precise sub-soil and soil treatments and to establish the most appropriate species selection for a particular site.  Utilisation of this technology should improve the general standard of grassed areas in schools as dependence on artificial fertilising is reduced.

Generally: tree planting improves the visual and physical amenity of a school with minimal interruption to functional flows and relationships.

• Locate trees at least 3.0m from any roof gutter - where soils are highly reactive to soil moisture levels, this distance may need to be increased (check adjacent development for any signs of cracking, etc.). 
• Trees in grass should be > 1.2m from adjacent paving, (although a wider separation would reduce damage from roots) and 1.5m minimum from other trees, to facilitate mowing.
• Trees in paving are usually limited to the building precinct:
  • ​Unit paving allowance of 2.0 x 2.0m may be installed around the base of the tree to maximise site availability and minimise soil compaction. 
  • In this situation, eliminate compost from the soil mixture to minimise differential settlement.
• Root barrier to be installed to minimum 500 mm depth using flexible polyplastic product. A ‘gap graded’ ‘structural soil’ mix is to be used in this location to allow an increase in the volume of soil provided for trees to root and minimise the incidence and severity of pavement damage due to root movement. Incorporate drainage at the bottom of the structural soil and connect to the stormwater system.
  • The selected stock should be advanced and tree guards provided, because of the high level of activity in these areas.
  • Ties should never be attached to the tree guards.
  • Installation of a watering system to distribute water, nutrients and oxygen evenly around the root ball will encourage deep root growth to avoid damaging the paving. Root directors may also be appropriate.
• Trees can contribute more to spaces between buildings than mass planted beds, by controlling the sun, providing a sense of scale, spatial definition, and the high aesthetic value of ever changing shadow pattern on pavement.
  • Distance between roof overhangs is to be greater than 6.0m where possible, to allow for tree planting.
  • Selection of tree species should take into account the size of the space plus climatic and soil factors. 
  • Sub-soil drainage is required to all trees in paving with pipe brought to surface (and capped) to allow for hand watering to subsurface

​92.06.01

Site planting should:

• Create a strong visual framework
• Define major functional units on the site and integrate the whole while acknowledging the pre-development patterns of vegetation
• Accommodate modified conditions on site resulting from development
• Take into account wind protection and excessive overshadowing of playing fields, plus the more obvious amenity of summer shade
• Help define movement and circulation

Site planting techniques should:

• Take into account existing soil conditions
• Avoid excessively deep excavation
• Brake up sub-grades to prevent “welling” around tree roots
• In very heavy soils, consider graded drip lines and/or soil mounding to enhance plant performance

Local native species should be used wherever they can effectively fulfil the design requirements. The order of preference for selection of species should be:

(1). Local habitat zone. (2). NSW  (3). Australian  (4) Exotic

Refer to the local Council for advice on plant species that are suited to local conditions (Native and Exotic species) and cross check to avoid potentially harmful varieties.

Where Australian native species are to be used:

• Modify fertiliser selection to suit
• In rural areas, rabbit protection may be necessary
• Use the smallest stock practicable

In the past, forestry tubes have been avoided because their small size rendered them vulnerable to accidental damage: now that the “Tuley Tube” is locally available, forestry tubes could be viable.  

When selecting tree and plant species for specific locations on school sites, the following must be considered:

• Trees that may shed large branches when under environmental stress should not be planted in school play or assembly areas, adjacent to buildings or in car parks. (Eucalyptus ssp. River Red Gum (camaldulensis), Lemon Scented Gum (citriodora), Spotted Gum (maculata), Mannifera (mannifera ssp.), Red Spotted Gum (maculosa), Mountain Ash (regnans), Candlebark Gum (rubida), Manna Gumm (viminalis), Coral Tree (Erythina ssp).
  • If a specimen of a species prone to limb drop exists as a mature tree on site, carefully consider its location relative to the proposed future use of the surrounding area. Review the design and species and assess the suitability for retention, with a view to minimising the potential risk.
  • Consult a qualified arborist to review existing trees and assess the risk, as well as provide management guidelines and measures to reduce stress and the potential for limb drop.
• Trees or Shrubs that may cause injury should not be positioned within assembly areas, adjacent to games courts and along circulation routes. The use of shrubs/trees that have thorns or prickly foliage, produce large fruit or cones are to be discouraged
• Trees with aggressive root systems should not be used as they can damage walls, paving or drainage pipes. Ie. Figs & Rubber Trees (Figis Sp.), Poplars (Populus Sp.), willows (Salix Sp.), Camphor Laurel (Cinnamomum Camphora) , Coral Trees (Erythrina), Black Locust (Rubinia Pseudoacacia).
• Avoid planting species where they will drop leaves to block roof gutters.  (Casuarina ssp., deciduous trees and climbers).
• To minimise the risk of termite infestation in buildings, improve the chances of termite detection by ensuring planting will not obscure the building edges, inhibit sub-floor ventilation for elevated floors and watering systems do not create damp conditions conducive to termites.
• Avoid poisonous or high allergy risk plant species. Refer to recommended planting lists as published by Kidsafe® and the NSW Asthma Foundation.
  • Plants known to be toxic, and especially those known to be toxic in small quantities, must not be used in the school landscape. Common toxic plants include:

    Common Name                              Botanic Name

Angels Trumpet                             Brugmansia x candida

Arum Lilies                                     Zantedeschia aethiopica

Castor Oil Plant                             Ricinus communis

Crepe Jasmine                             Tabernaemontana divaricata

Daphne                                           Daphne mezereum

Deadly Nightshade                       Atropa belladonna

English Yew                                  Taxus baccata

Hemlock                                        Conium maculatum

Lily of the Valley                            Convallaria majalis

Native Loquat                                Eriobotrya japonica

Oleander                                        Nerum oleander

Poinsettia                                       Euphorbis pulcherrima

    Rhus                                                Toxicodendron succedaneum

    Rosary Bean                                  Abrus precatorius

Golden Chain Tree                       Laburnum anagyroides

Yellow Oleander                           Thevetia ssp.

White Cedar                                   Melia azeradarach var. australasica     

Note: This list is not exhaustive. It is the responsibility of the designer to ensure that selected plant species are not known to be toxic at the time of undertaking the design.