Josh shows us that there’s a heap of wonderful WA native plants that are just perfect for pots, and gets some pointers from a plant professional.
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Many seasoned gardeners will tell you that Australian native plants will fail to thrive in pots and should only ever be planted in the ground, but Josh is in the Roe Gardens in Kings Park to bust this myth. And who better to show him how it’s done then Dr Tony Scalzo, a key component of the plant breeding and nursery program at Kings Park for over 25 years.
To the concerns around growing natives in pots, Tony says “to be honest, there are a whole bunch of WA natives that are really tricky to grow in gardens, and have proven much easier to grow in pots”. These include the Orange Stars (Hibbertia stelarris) and any number of the Western Australian Stylidium sp., more commonly known as Trigger Plants.
For Tony, there can be clear advantages to growing many WA wonders in containers. “You are better able to manipulate the conditions the plant requires in a pot over a garden setting. That could be location, light and drainage…. but a lot of it comes down to the growing medium”.
“I think this is why people believe that natives don’t do well in pots, it’s all about the potting mix, it has to be right to ensure success” says Tony. He has found that many mixes sold commercially as suitable for potted natives are simply too high in organic matter, and have a tendency to “clag up”, effectively turning the mix to sludge and “shortening the life of the plants”. Instead, Tony suggests amending and adjusting these potting mixes with the addition of a coarse material, either coarse river sand, or chunky perlite. “What this does is lighten the mix, essentially adding space for air” he says. “Air is the forgotten ingredient in a good potting mix - you want to aim for about 25% of the mix being air, especially when you are growing WA natives”.
The soil amendments help improve the drainage of the mix as well, however Tony has a clever trick to ensure pots are draining properly, and roots run no risk of becoming waterlogged and suffering root rot. “We use a small rocket pot, and we will place that upside down over the drainage hole of the main pot. I’ll pack that in and secure it with some coarse river sand or course perlite, and then fill with our amended potting mix”.
For gardeners new to natives, there are loads of WA natives that Tony recommends that are available in good nurseries around the country, not just WA. “The smaller Kangaroo Paw hybrids are fantastic, and they have a huge range in which they’ll thrive - my mother grows a Kings Park Royale in a pot in Melbourne, and it’s a beauty”. Others to try on Tony’s top list include Calytrix, compact Scaevolas, Darwinia, Conostylis, Hibbertia and Hoveas.
Once planted, the pots are topped with an inorganic mulch, either a coarse river sand or pea gravel. Tony explains “I prefer inorganic to organic mulch for natives, they just add too much organic matter to the mix as they break down. Plus, the pea gravel is easy to weed, helps conserve water and looks great”.
So, what about the watering? The tips for potted success here are simple - water regularly, every second day or so, and daily in hot weather.
Other regular maintenance to keep potted natives in good nick involves fertilising, with a twice-yearly application of a slow release fertiliser suitable or natives - “give them the appropriate dose in spring, and autumn and they’ll be happy all year”.
When picking a suitable pot to plant natives into, Tony recommends looking for “V-shaped pots, those that are wider at the top than the bottom. This will allow you to easily remove the plant from the pot for root pruning or repotting every three years or so”. He does recommend that, if using terracotta pots for natives, that the inside be sealed with pot sealer, otherwise they can be to porous and dry out too quickly.
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