With the ongoing discussions about some exotic species becoming problematic in parts of Australia, I felt it was time to reveal that while I love native plants, I also have a deep appreciation for many exotic species and believe they can coexist harmoniously.
The Native Plant Misconception
It’s important to recognise that just because a plant is native doesn’t mean it won’t become a weed. Take the Cootamundra Wattle (Acacia baileyana) as an example. This beautiful, fast-growing acacia is naturally restricted to the South Western Slopes of New South Wales. When planted in higher rainfall areas, it can aggressively invade surrounding bushland, self-seed, and become a nuisance.
Another misconception about native plants is that they require little to no maintenance. A native garden, like any other garden, requires effort. This includes:
Soil Cultivation: Regularly improving soil with compost and organic mulch.
Fertilising: Using products like Organic Link at the start of each season and supplementing with regular liquid fertilising.
Maintenance: Trimming and replacing plants as weather conditions change.
Responsibility
People must start to take responsibility for our plants and gardens. For instance, Syngoniums, a popular houseplant, are classified as weeds. Do we stop cultivating this plant, or do we educate and ensure responsible care and correct disposal, if needed? As a professional horticulturalist, I explain the potential pitfalls and dangers of allowing such plants into the wild. I expect their new owners to trim and care for them to prevent them from becoming out of control. I expect people to allow themselves to be educated and take on that advice. You cannot buy a climber and then get upset when it climbs.
Choosing the Right Plants
Reputable Sources: I only purchase plants from reputable sellers. For example, seed-grown vinca (which I do not sell) can be a weed, but with modern horticultural advancements, sterilised vinca won’t usually last longer than 6-12 months (this is what I stock).
Local Availability: Many Southeast Queensland natives are not commercially available because they are hard to cultivate in large numbers or aren’t as visually appealing as their Western Australian counterparts. Thus, a native garden in Ipswich might consist of 20 Western Australian and South Australian natives and only a couple of Southeast Queensland natives.
Genetic Dilution in Local Australian Plants
Genetic dilution refers to the weakening or loss of genetic diversity in local native plant populations due to cross-breeding with introduced species from other areas or non-native species. This can lead to several ecological and evolutionary problems, including reduced adaptability to local conditions and the loss of unique genetic traits.
An example of this happening is with the Australian native Corymbia torelliana, commonly known as Cadaghi. It is native to northern Queensland, Australia, and has been widely planted outside its native range due to its fast growth, aesthetic appeal, and usefulness in timber production.
Corymbia torelliana can hybridise with closely related species, such as other Corymbia species and some Eucalyptus species. When this occurs, the genetic material of Corymbia torelliana mixes with that of the native species, resulting in hybrid offspring. These hybrid offspring may exhibit reduced fitness compared to pure native species, including traits such as lower resistance to local pests and diseases, or reduced adaptability to local soil and climate conditions.
The genetic dilution of native species can also lead to a reduction in biodiversity, potentially disrupting ecosystem functions such as nutrient cycling, water regulation, and habitat and food provision for other species.
Corymbia torelliana produces a large amount of pollen, which can be dispersed over long distances by wind or pollinators like bees. This increases the likelihood of cross-pollination with native species over longer distances. Just one tree can affect a very large area.
The Role of Exotic Plants
Native and European plants can be used together. Many fruit trees and vegetables aren't native, but that doesn't mean we should stop growing them. Many herbs, like garden mint, and comfrey, can become weeds, yet we don’t stop cultivating them. Instead, we focus on education and responsibility.
I have personally found Camellia sasanqua flowers and bacopa (both exotic) are a preferred flower for my native bees. Lemon Balm (Melissa officinalis) was traditionally used by the ancient bee keepers. They used to rub the crushed leaves on the beehives to encourage the domesticated bees to return to their hives. They also believed that the lemon balm would also bring new bees to the hive.
Creating a garden, whether it be native or a combination, requires thoughtful planning and effort, but the results are worth it. By understanding the specific needs of our environment and taking responsibility for our plant choices, we can create beautiful, sustainable gardens that celebrate both native and exotic species. Let’s continue to educate ourselves and others while embracing the diversity that makes our gardens thrive.