What’s the Best Mulch for Your Garden? A Practical Comparison

Mulching your garden and landscape serves many purposes. There are various types of mulch available, and in this blog, we'll break down the different options and help you figure out which one is best for your situation. Skip to the factsheet if you're not interested in the breakdown of 'what, why and how'.

Mulch Options

Mulch ranges from very fine to coarse carbon-rich organic material including straw, lucerne/ alfalfa, forest mulch or double grind forest mulch.

Left to right: Straw mulch on a veggie garden, double-grind mulch used throughout an orchard and forest mulch for bank retention

Mulching a garden provides plenty of functions:

• Increases organic material on top of and integrated within the soil

• Encourages microbial activity and decomposition

• Insulates the soil, regulates temperature

• Increases water holding capacity of the soil

• Reduces germination and cover of weeds

• Prevents erosion and top soil loss

• Can be used as a soft path

• Transforms a space with a clean ground layer

Conversely, mulching can be of detriment to some plants and your broader garden due to:

• Encourage fungal attack or collar rot

• Accidental introduction of weeds

• Restrict water infiltration

You can control adverse impacts by considering the plants you're surrounding with mulch and if they're susceptible to rot (such as Solanaceae species), leave a 10cm gap between the mulch and trunk/ stem. We recommend you minimise late afternoon to night watering, facilitate good airflow and prevent other parts of the plant from touching the ground to reduce fungal attacks and root rot.

Preventing the introduction of weed seed is simply about being selective with your source, particularly if it's green waste or from an arborist. Don't be afraid to ask a supplier 'do you know where this came from? Does this have weed seed?'.

Finally, maintaining water infiltration is achieved with a suitable depth of mulch that offers the benefits without blocking water. You can test the depth of application with trial and error by observing subsequent watering of your garden. Preferably, test the water infiltration with a hose, irrigation or watering can as you're applying the mulch in the first instance and determine a suitable thickness. As a rule of thumb, aim for 50mm.

Mulch or Compost

Compost is the result of a biological decomposition process where nitrogen-rich materials, like food scraps or grass clippings, are combined with carbon-rich materials, such as dry leaves or straw. Microbes break down this mixture over time, transforming it into a nutrient-rich product full of microbial life and humus, ideal for enriching soil. While some mulches, such as straw, can be carbon-rich ingredients in a compost pile, their primary role in gardening is to retain moisture, suppress weeds, and regulate soil temperature, rather than to decompose into a soil amendment like compost.

Therefore, you would apply mulch when there isn't a need for nutrient enrichment or you are looking for a more affordable or immediate option to cover your soil. I often apply both, compost around the dripline of my plants and mulch elsewhere.

Choosing the Best Mulch for your Garden: Straw vs Forest vs Double-Grind

Here’s a comparison of three common mulch types we use and recommend you choose as the best mulch for your garden:

Straw Mulch – Bacterial Boost for Fast Growers

Straw mulch is ideal for high-turnover growing spaces like veggie patches and annual flower beds. It decomposes quickly, feeding bacteria-dominant soils, which are well-suited to fast-growing, shallow-rooted plants.

• Fungal:bacterial ratio: ~1:2 to 1:3 (Bacterial dominant)

• Decomposition rate: Fast – breaks down in 2–6 months

• Best used for:

  • Annual vegetable beds

  • Soil building in early-stage garden development

  • Areas needing quick nutrient cycling

Lightweight and easy to apply, straw mulch is a great choice when you want rapid soil activity and regular bed turnover. Just be prepared to top it up more frequently, especially in hot or wet conditions.

Forest Mulch – Long-Term Soil Health and Habitat

Forest mulch, made from mixed tree trimmings and coarse organic matter, mimics the natural forest floor. It encourages a fungally-dominant soil web, ideal for trees, shrubs, and perennial landscapes.

• Fungal:bacterial ratio: ~2:1 to 5:1 (Fungal dominant)

• Decomposition rate: Slow to Moderate – breaks down over 12–24+ months

• Best used for:

  • Native gardens and bushland restoration

  • Perennial plantings, hedgerows, and food forests

  • Erosion control and moisture retention

  • Pathways

    
    

This mulch is a powerhouse for building low-maintenance, resilient systems and fostering mycorrhizal networks—but it’s not ideal for quick-growing crops or compact planting rows.

Double-Grind Mulch – The Middle Ground

Double-grind mulch is a refined version of forest mulch, ground twice for a finer, more uniform texture. This increases the decomposition rate and strikes a balance between bacterial and fungal activity.

• Fungal:bacterial Ratio: ~1:1 to 2:1 (Balanced to mildly fungal)

• Decomposition rate: Moderate – breaks down in 6–12 months

• Best used for:

  • Young trees and ornamental shrubs

  • Mixed-use gardens with both edibles and perennials

  • When you want to improve soil yet

    
    

Its tidier look and mid-speed breakdown make it a great all-rounder—particularly in residential gardens or places where aesthetics and function need to go hand in hand.

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Mulch Factsheets

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Conclusion

Mulch isn't just a finishing touch—it’s an active layer in your garden that influences soil health, plant performance, and long-term landscape resilience. By understanding how different mulches interact with the soil food web and decompose over time, you can select the right type to match your garden’s needs. Whether you're nurturing a lush veggie patch, establishing perennial borders, or building a low-maintenance food forest, choosing the right mulch will support your goals.

At Holhab, mulching is honestly one of our favourite jobs in the garden as it provides an instant transformation whilst improves the long term health of the soil. In our eyes, an afternoon spent spreading mulch with a pitchfork and wheelbarrow is an afternoon well spent.

If you’re still unsure which option fits your landscape—or want help designing a system that works with nature— contact Holhab today.