Which Black-eyed Susan?

Why we use scientific names

What’s in a name? There’s a beautiful, vulnerable plant that grows locally on the West Ridge, on the low-nutrient soils of the Awaba Soil Landscape. It’s a clumping shrub, with single or multiple stems that stretch 30–60 cm long. The stems are often leafless, edged with narrow wings that give them an angular look. Along the stems, delicate flowers droop downwards, usually in fours, with petals ranging from white to soft pink through to deep purple.

This plant is commonly known as Black-eyed Susan, but its scientific name is Tetratheca juncea, affectionately called TJ.

BUT there’s also an invasive weed with the very same common name. This Black-eyed Susan (Thunbergia alata) is a vigorous perennial climber, scrambling 3–4 metres high . Its triangular leaves form dense mats, while its orange or yellow flowers with dark throats are eye-catching but destructive. After flowering, hairy seed capsules form, helping it spread. More often though, its escape comes via dumped garden waste. On Coal Point it is a major problem, smothering native plants.

And if that wasn’t confusing enough, Rudbeckia hirta, another “Black-eyed Susan,” also known as Yellow Coneflower, hails from North America. It’s a daisy-like plant growing up to a metre tall, with many cultivated varieties.

So we have three very different plants, all called Black-eyed Susan. This is why Landcare uses scientific names. Botanical names cut through the confusion, and once you start using them, it’s a bit like learning a new language. It’s good for the brain, helps us be precise, and even opens the stories behind the names:

• Tetratheca = “four cells or lobes” for the four-petalled flower
• juncea = “rush-like,” describing its long, slender stems

While Tetratheca juncea isn’t currently available for sale, there are many local native plants that make excellent understorey options for home gardens. You can find tubestock at the Lake Macquarie Landcare Nursery, 80 Toronto Road, Booragul, open Tuesdays and Wednesdays, 8.30am–3pm, or by appointment.

All the details on the very special Tetratheca juncea are here 

Alternatives to plant instead of Thunbergia alata are here