Westgate Park is not a remnant or natural site. Much of the soil is foreign to the site, and it varies greatly. Upon European colonisation, Westgate Park was a coastal swampland, with sandy soils. While some of the soil and vegetation remains, most of the landforms have been significantly altered, with unnaturally steep hills scattered throughout the park.
The soils in the park can vary just a few metres apart, depending on what was dumped at the site when the park was created in 1985. This makes it difficult to develop a weed treatment strategy as soil types often alter how we deal with weeds.
Mulch, at the appropriate depth, prevents the germinating weed seeds under the mulch from being able to penetrate the mulch. This means that while they might germinate under the mulch, they will soon die. After a number of years, the mulch does eventually break down, so then the native grasses and wildflowers we have planted can self-seed.
Mulch also protects the soil from drying out by being an insulating ‘blanket’. At the appropriate depth, rain can still penetrate the mulch and get to the soil, but when the sun comes out, the soil is prevented from drying out as quickly.
Much of the soil at Westgate Park has been compacted by machines, cars and bikes. Mulch provides habitat to insects and worms which will loosen the soil’s structure, and which helps plants develop deeper and stronger root systems.
When you wouldn’t mulch
Much of Australia’s soils are poor in nutrients. This is because we have had little geological activity, such as volcanoes and glaciers in the last few hundred millennia. Adding mulch changes the nutrients in the soil. Australian plants thrive in the poor soils, and added nutrients generally allow weeds to survive and the native plants suffer. However, as Westgate Park has varied soil that is not natural to the site, the altered nutrient levels have not generally been a problem for this park.
Introducing organic material can bring in fungus and insects that are not natural or helpful to the site. Again, as Westgate Park is not a naturally created site, the benefits of using mulch far out weigh the negatives.
In natural sites leaf litter provides a mulch. Some of the sites we planted years ago now have trees and plants which are old enough to provide their own mulch, and will not need mulching again.
Mulch can cause ‘trunk rot’ of young plants or even trees if placed too close to the stem/trunk. This is one reason we use cartons and tree guards around plants. It is important when decartoning plants to ensure that the mulch is not too close to the base of the plant.
How to mulch
Mulch needs to be spread to the right depth for the site and task at hand. The depth of the mulch for different sites throughout the park will vary according to the purpose of the mulch.
We ‘blanket mulch’ to a depth of 7-9cms over large areas to be planted into at a later stage. This depth allows the rain to penetrate the soil, while still being deep enough to kill the weed seeds underneath as they germinate.
We often also ‘spot’ mulch trees that we have planted throughout the park. In this situation the only purpose of the mulch is to prevent the soil drying out. Often these trees are planted into very weedy areas that we intend to ‘blanket’ mulch at a later stage. The mulch should be spread in a circle around the young tree to a width of at least 1 metre. As tree roots extend a large distance around the trunk of the tree, 1 metre or more should provide a good area of moisture for young trees roots. A depth of 7-9 cms is used for this purpose to allow the rain to penetrate the mulch into the soil.
Sometimes we use weeds as spot mulch in areas where weeds surround the trees as we wouldn’t want to spread weed seeds in areas that have been ‘blanket’ mulched. It also makes use of the one thing we have in abundance at Westgate Park – weeds.
There are a few sites which have been blanket mulched where we still spot mulch individual plants. This is often in sites where the soil has become hydrophobic – or ‘scared’ of water. In these sites the soil repels the water, and when it rains the soil runs off the surface and does not penetrate into the soil. In these sites we need to be careful of other plants surrounding the area we are mulching
Roads and paths
On occasion we mulch paths and roads to prevent weeds germinating. On these areas we are not concerned with rain penetrating the soil. As the only purpose of this mulch is to prevent weeds, we can spread the mulch to a depth of 10-15 cm on these sites.
Sometimes we need to remulch an area. This can be because the mulch was not spread to the correct depth initially, the mulch has eroded due to traffic, falling down a slope, or rabbits scratching in the mulch, or because when planting much of the soil has been lifted on top of the mulch creating a weed problem and allowing the soil to dry out. We rarely need to mulch a site more than twice and usually remulching only occurs in areas near paths and roads. After a site has been planted fully with trees, grasses, wildflowers and groundcovers, it will provide it’s own leaf litter mulch, and will only need remulching on path edges if that.
When we are remulching along paths we try to mulch to a depth of 9 cms, and try to compact the edge to prevent it slipping onto the path. When we are remulching thickly planted areas we mulch to a depth of 2-5 cms just to prevent weeds germinating and provide some protection from the soil drying out. It’s important when remulching planted areas to be careful not to cover the plants with mulch, or put the mulch too close to the trunks and stems of plants.
The person holding the rake is responsible for keeping the depth consistent throughout the site. This person should instruct the wheelbarrow movers to dump loads where the mulch is thin or non-existent. As the site may have a few lumps and bumps, it’s important for the raker to take these into consideration, so that the lumps don’t end up having little mulch on them.
Dust – In dry times the mulch can be very dusty and you may wish to use a dust mask to prevent breathing in particles of dust. On windy days you will need to work above the wind and ensure none of your colleagues are in the wind path, or better yet, leave the mulch to a less windy day.
Your body – Mulching can be quite heavy work. It can place strain on your arms and, shoulders and back. It’s important to always look after your body and work in a way which minimises the impact on your body. Remember to bend with your knees, and to keep twisting your back to a minimum. Changing from filling wheelbarrows to moving wheelbarrows for example will also create less strain on your body.
Be lazy!!! – It’s also worthwhile to think of the ‘laziest’ way to complete a task while still doing the task properly. Having the wheelbarrows close by when you are filling them, turning the wheelbarrows around to face the direction I which they are going to be moved before filling them, are ways in which you can do it as ‘lazily’ as possible. Having the wheelbarrows 2 metres away form the pile from which you are filling them makes the work harder, puts more strain on your body, and is usually unnecessary.
Forks – The forks are sharp, and it is important to keep them away from the path, and always turned upside down if placed on the ground, or stuck upright in the mulch. There are also heavy, so just take a load you can comfortably manage from the pile in the fork.
Wheelbarrows – Sometimes the wheelbarrows can be hard to handle or quite heavy. Again, ask the person filling the barrows to fill to what you comfortably manage. When moving the wheelbarrows it can be difficult to get them exactly where you want them, and the mulch might fall where you didn’t want it. The person raking should be able to move it into the right spot, so just tell them it’s fallen where you didn’t mean it to. When moving wheelbarrows on slopes it will often fall where you don’t want it to, and just remember it is much easier to rake loads down the hill than up the hill.
Bucket mulching – Bucket mulching is heavy work, and often needs to be walked a distance or on a slope. It is best to half fill the buckets or carry a bucket with another person, and ask the supervisor to drive the trailer closer to where the mulch is being dumped.
Never do something that causes you pain or strain. Change jobs, ask for help, or if you can’t find a way to do it, ask your supervisor if there is something else you can do.
Work as a team and admire your work!
It helps to work as a team and to communicate clearly and politely to each other so that work can be done efficiently and safely. But most importantly, when working with a team of people, once the barrows and forks are down, look at what you and your team have accomplished, and know that you have been working to make yet another small but worthwhile difference to your local environment!!