Mulch Trial

Planting in Fall Zones

What are we trying to do?

We are trying to determine the best growth conditions for non-woody plants (e.g. small shrubs and grasses) in playground mulch. 

Who is doing this?

This trial has been made possible through a collaboration between:

mulch trial logo
  • Landscape architects (Fiona Robbé Landscape Architecture)
  • Landscape suppliers (The Hills Bark Blower).
  • Plant breeders and researchers (Ozbreed).
  • Acousto-Scan 7025 Sports Testing Laboratory.

Why are we doing this?

There is demand and interest in growing non-woody plants in playground mulch in and around play equipment, including fall zones.

To provide playground designers and providers with confidence and technical information of how to plant in mulched fall zones of playground equipment.

The benefits of planting in playground mulch…


  • Planted areas can contribute greatly to a child’s sense of inclusion in a play environment by reinforcing boundaries, providing familiar visual cues and contrasts, and by providing sensory delight
  • Plants add diversity to any play environment through colour, texture, smell, seasonal changes, movement and interesting forms. Judicious planting in less trafficked parts of fall zones can contribute to all domains of play. For example:
  • Imaginative outcomes are richer, especially as plants provide loose parts.
  • Plants cover the full range of sensory play.
  • Plants stimulate cognitive/intellectual thought processes, especially in regard to problem solving.
  • Plants encourage physical play outcomes – kids are compelled to interact with naturally planted environments, e.g. tactile experience – children can feel the difference between the spiky leaves of Westringia Naringa and the smooth leaves of Lomandra longifolia ‘Tanika’.
  • Plants get children talking and questioning, promoting social play.
  • Interaction with plants is always a significant theme in any playground consultative session; children are eloquent about touching, picking and simply being amongst plants as part of their overall play experiences.

Aesthetics and function

Often, large bare fall zones make playgrounds appear open, lacking intrigue and interest; it is anticipated that planting in playgrounds, including within fall zones, will be a simple and inexpensive way of softening the appearance of this typically bland playground landscape.

Planting better defines the spatial qualities within a playground, by demarcating different zones of use within the playground (e.g. access paths can be established as lines of mulch between planted areas).


  • Planted fall zones are safer than mulch fall zones.

Natural/historical and cultural aspects

Plants often form part of the natural/historical and cultural aspects of any play environment. The ability to plant in fall zones will provide an opportunity to include more plants within play environments without having to increase the site area.

The environment and sustainabilityPlants are a positive net sink for atmospheric CO2, and create small ecosystems within playgrounds.

Plants absorb water from mulch and knit mulch together with their roots, meaning that playground mulch will need less topping up over the years. Furthermore, tests on plant root zones yielded some of the best critical fall height results. While plants may need additional watering in the establishment period, maintenance of the playground over time will diminish as the plants stabilise the mulch. Even dead plants provide positive critical fall height results, and hence do not need removal.

Why is this research innovative and important?

  • The trial was designed to be thorough in order to confidently contribute to and support truly innovative design approaches that are possible in the context of Australian playground provision.
  • It is innovative in that, as far as the team is aware, such testing has not been undertaken in Australia before.
  • The successful results will support play providers to plant in less trafficked parts of fall zones.


 Specific aims of the trial

To provide factual evidence that:

  • 300mm deep playground mulch can support the establishment and growth of non-woody plants.
  • The established plants and their rootzones are a safe medium for children to fall on.
  • Plants do not diminish the impact attenuation properties of the playground mulch in which they are growing.

Materials used:

  • Playbark pinebark mulch.
  • Port Stephens pine mulch.

Plants used:

  • Westringia Naringa.
  • Lomandra longifolia ‘Tanika’.


Port Stephens pine mulch alone: 5.9m critical fall height.

Port Stephens pine mulch on (dead) Lomandra: 6.2m; on Westringia: 5.9m.

Playbark pinebark mulch alone: 3.2m.

Playbark pinebark mulch on Lomandra: 6.2m.

  • Non-woody plants in 300mm deep mulched fall zones provide pleasing and compliant results as regards Gmax and HIC values when tested in accordance with AS/NZS:4422 1996.
  • Plants can establish in 300mm deep mulch without significant plant loss or nutrient deficiencies.
  • It is safe to fall onto soft leaved plants in fall zones.
  • Plants do not diminish the critical fall height of mulched fall zones; rather, they can add to it!
  • Therefore, these results prove that plants can be safely used in mulched fall zones within playgrounds.

* It is worthwhile to note that the Tanikas planted on a collar of soil in Playbark pinebark mulch yielded the highest critical fall height (i.e. 6.2m), and were also the fastest plants to establish. This finding is encouraging as it means that this method of planting will result in plants being established faster, and therefore less vulnerable to being pulled out by playground users.