Gardening Myths: The Stories We Tell Ourselves

Planting myths often contain a seed of truth, but as any gardener knows, the real story is rarely so simple. In gardening, there’s rarely a one-size-fits-all rule. What works in one garden, climate, or soil type might be a disaster in another.

Let’s talk horticultural myths and gardening “truths” that aren’t quite right…

What have you believed or done in the garden that turned out to be misunderstood, outdated, or just plain wrong? Here are a few confessions to get us started:

Myth

Potting mix feeds your plants for 18 months

When potting mix says “feeds for 18 months,” that’s from the date of manufacture, not the day you open the bag. And no… they don’t put the date of manufacture anywhere on the packaging.

That’s why we always recommend feeding when planting, using something like Organic Link so you know exactly when the last feed happened. If in doubt, reapply every three months or with the turn of each season to keep nutrients consistent.

Myth

Full sun means all-day blazing sun

When a plant label says “full sun,” it simply means the plant needs at least 6 hours of direct sunlight per day. But not all sun is created equal.

Ipswich sun in December is a whole lot fiercer than Melbourne sun in December. So generally, if a plant tag says “full sun,” aim for sun-up to midday in hot climates — that’s a safe six hours for most plants.

And here’s the kicker: some plants can handle 12+ hours of blazing sunlight a day and thrive in it. Unfortunately, they’re labelled exactly the same as more delicate “morning sun only” plants. No wonder it gets confusing!

This is exactly why plant labels aren’t your only resource. Chatting to your local garden centre and their qualified horticulturists is the best way to get location-specific advice based on real experience.

Myth

Banana peels are a great potassium fertiliser

Banana peels just don’t have enough potassium in the peel to make much difference when used directly on your garden.

Let’s break it down: banana peels contain about 78mg of potassium per 100g, while a proper potassium fertiliser contains thousands of milligrams per application, plus it’s in a form that plants can actually absorb.

So while it sounds lovely to tuck a banana peel under a plant, you’re better off adding it to your compost where it can break down with other organic matter and contribute to long-term soil health.

If your plant needs potassium? Reach for a specific potassium-based fertiliser like Sulphate of Potash or Silica and Potash, especially during flowering and fruiting seasons.

The takeaway?

Read the label. Read your climate. And talk to someone who’s been there, killed that, and figured it out the hard way!

Have a gardening myth you’ve fallen for — or one you’re not sure about? Pop in and see us at Trevallan, or drop a comment below. We’d love to help you sort fact from fiction.

I’ve recently covered a few more myths you might like to explore

• Adding compost to your planting hole

• whether honey really works as a cutting compound

• the truth about molasses in the garden

• Ants and Vaseline

  Check them out and keep growing smarter!

Not All Potting Mixes Are Created Equal

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A post shared by Tim’s Garden Centre (@timsgardencentre)

Lately, there’s been a lot of conversation around potting mixes, thanks to Tim’s Garden Centre running a potting mix experiment. It’s a great conversation starter—but like many things in gardening, there’s more to the story than meets the eye.

What Tim’s Experiment Highlights

Tim’s trial uses 8 different Australian Standard Premium Potting Mixes, with dwarf Cos Lettuce planted directly into the bags. It’s simple and visual, and it highlights something really important—not all potting mixes perform the same, even if they meet the same standard.

In fact, some mixes that performed well in a previous trial are struggling this time around, and vice versa.

What does that tell us? The Australian Standard itself might not be enough.

What Tim Didn’t Mention

While the experiment raises valid concerns about consistency, it leaves out some critical context that gardeners deserve to know:

• How long had each bag been sitting on the shelf before purchase? Age impacts nutrient levels, moisture retention, and overall performance. Cheaper mixes tend to sell faster, so they’re often fresher. Premium more expensive mixes, on the other hand, might sit longer, especially in big box stores where stock turnover may be slower for a more expensive range.

• Where and how was the potting mix stored? Potting mixes stored outside in all weather conditions start to break down faster. This breakdown attracts fungus gnats, which thrive in moist, organic material.

• We’ve even seen discontinued mixes on shelves years after they were removed from production. Old, compacted, and improperly stored potting mix isn’t a recipe for success.

Understanding the Australian Standard

This raises an important question—what do the Australian Standards for potting mixes actually cover? Most people assume they guarantee quality, but in reality, the standards primarily focus on:

• Physical properties (drainage, air space, particle size)

• Basic nutrient levels

• pH balance

What they don’t cover in detail is storage conditions or maximum shelf life. That’s a major gap, because even the best potting mix can deteriorate if stored poorly or for too long.

So, What is Potting Mix, Really?

This is a perfect time to go back to basics:
Potting mix isn’t just dirt in a bag—it’s a specially formulated growing medium designed to support plant roots in containers. It’s lightweight, well-draining, and holds moisture without becoming waterlogged.

Garden soil, on the other hand, is heavy, compacted, and often poorly suited to containers. This is something I covered in my blog Going Potty, if you want to dive deeper.

Why I Stock Searles Platinum Potting Mix (and Not Searles Premium Potting Mix)

Tim’s trial uses Searles Premium Potting Mix, which is a high-quality potting mix containing a blend of organic compost, humus, trace elements, minerals, peat, coir, and Zeolite, along with 8 months of Robust® Controlled Release Fertiliser. It’s a solid mix that meets the Australian Premium Standard, but at Trevallan, I go a step further.

I choose to stock Searles Platinum Potting Mix®, the apex potting mix designed for long-term success. It’s professionally formulated using only the highest grade ingredients and advanced blending techniques, honed over decades of experience. Platinum doesn’t just meet the standard—it exceeds it.

Searles Platinum Potting Mix (Stocked at Trevallan)

• 18 Month Controlled Release Fertiliser

• Contains Searles Flourish® Soluble Plant Food & Robust® Controlled Release Fertiliser

• Double Strength Penetraide® Re-Wetting Granules and Water Crystals

• Enriched with Potash, Fish, Seaweed, and Volcanic Rock Minerals

• Enhanced with Zeolite, Trace Elements & Minerals

• Suitable for indoor plants, ferns, potted colour, hanging baskets, shadehouse plants, and more

This is why not all potting mixes are created equal—and why choosing a higher-grade mix sets your plants up for success from day one.

The Real Takeaway

It’s easy to blame a plant for failing, but the real culprit might be the mix it’s growing in—or how that mix was handled before you even brought it home. This is why expert advice matters and why I’m always happy to explain the differences between products I stock.

This isn’t about saying one retailer is better than another, it’s about educating gardeners so they understand that not all potting mixes are created equal. If we want people to succeed in gardening (and keep gardening!), they need honest, clear information, something the industry as a whole needs to get better at providing.

If you want to know which potting mixes I recommend (and why), visit me at Trevallan. And if you missed my latest blog about the true cost of plants and why expert advice matters, you can find it here: True Cost of Greenlife

Gardening success starts with good soil—and that starts with knowing what’s in your potting mix.