A Visit to the Queensland Garden Show

The Queensland Garden Show at Nambour once again proved why it is regarded as one of Australia's premier gardening events. There was something to interest every gardener, from beginners to experienced horticulturists.

One of the most popular attractions was the Plant Clinic, where visitors could receive free expert advice on everything from diagnosing fruit tree problems to identifying insects and diseases affecting their gardens.

A novel attraction was the Coffee Cup Refill Station. Instead of another cup of coffee, visitors could refill their cup with quality potting mix and take home a free seedling—a clever idea that was well received by gardening enthusiasts.

The Kitchen Garden section featured GROW, which offered a complimentary organic foliar spray with every plant purchased. Throughout the show there was an outstanding selection of plants, along with cooking demonstrations and presentations by many knowledgeable speakers.

Visitors to the Queensland Garden Show at Nambour are spoiled for choice each year. From expert plant advice and gardening demonstrations to hundreds of quality plants and displays, the show is a treasure trove of ideas for home gardeners.

One of the highlights for us was a presentation by horticultural lecturer Matthew Carroll (TAFE Ryde), who explained the science behind successful potting mixes. While gardeners often focus on watering and fertilising, Matthew reminded us that the potting mix itself is one of the most important ingredients for healthy plants.

His presentation reinforced many of the principles that organic gardeners have practised for years.

What Makes a Great Potting Mix? Lessons from the Queensland Garden Show

Why Potting Mix Matters

Unlike garden soil, a potting mix has four important jobs:

• support the plant
• supply water
• provide oxygen to the roots
• hold nutrients until the plant needs them.

If one of these is lacking, plant growth suffers.

The biggest surprise for many gardeners is that air is just as important as water. Roots cannot survive in permanently wet conditions because they need oxygen to breathe.

The Secret Ingredient is Air

One of Matthew's strongest messages was that healthy potting mixes contain thousands of tiny air spaces.

These air pockets:

• encourage vigorous root growth
• reduce root diseases
• improve nutrient uptake
• prevent waterlogging.

Many gardeners think adding extra compost will improve a potting mix. Unfortunately, too much compost can fill these valuable air spaces and leave roots sitting in wet conditions.

Quality Ingredients Make the Difference

Matthew explained why premium potting mixes generally perform better than cheaper products.

Good mixes commonly contain:

• composted pine bark
• coir (coconut fibre)
• perlite
• vermiculite
• pumice
• controlled-release fertiliser.

These ingredients stay open and stable, allowing roots to breathe.

Cheaper mixes often contain mixed wood waste that breaks down quickly. As the material decomposes, the mix shrinks and becomes compacted, reducing oxygen around the roots.

Tips for Buying Potting Mix

When purchasing potting mix:

✔ Choose premium products whenever possible.

✔ Look for consistent texture and particle size.

✔ Buy from suppliers with good stock turnover.

✔ Store bags out of direct weather.

✔ Remember that controlled-release fertiliser begins working once the mix becomes wet, so older bags may not provide nutrients for as long.

Can Organic Gardeners Improve Commercial Potting Mix?

Absolutely.

Organic gardeners can improve many commercial mixes by adding modest amounts of:

• worm castings
• mature compost
• biochar
• compost extracts
• fish hydrolysate
• liquid sea minerals.

The important point is moderation. These additions should support biology without reducing the air spaces that roots require.

Practical Tips from the Presentation

Matthew shared several useful tips that home gardeners can apply immediately.

• Soak compressed coir before using it.
• Wet perlite before handling to reduce dust.
• Reapply a wetting agent every six months.
• Before repotting, soak the old root ball in water containing wetting agent.
• Use sterile propagation mix for seeds and cuttings.
• Match the potting mix to the type of plant.

BOGI's View

At Bundaberg Organic Gardeners Inc., we believe healthy plants begin with healthy soil—or, in the case of containers, a healthy growing medium.

A quality potting mix provides the structure that roots need, while organic amendments encourage the living biology that feeds plants naturally.

The two approaches complement one another beautifully.

A premium potting mix provides the physical foundation, while compost, worm castings, sea minerals, biochar and organic fertilisers build a thriving microbial community that supports long-term plant health.

As Matthew Carroll reminded us, the best fertiliser in the world cannot compensate for a poor potting mix. Healthy roots need air every bit as much as they need water.

Final Thoughts

The Queensland Garden Show always provides plenty of inspiration, and this presentation was no exception. Whether you're growing vegetables, herbs, flowering plants or native species, starting with the right potting mix is one of the simplest ways to improve your success.

For organic gardeners, combining a high-quality growing medium with natural soil-building practices creates healthier plants, stronger root systems and more resilient gardens.