Illawarra is home to an immense range of fern species, and we are lucky to live in the midst of massive fern abundance and diversity. New species are added to the list occasionally, such as when Dr Kevin Mills recently published his book South Coast Ferns and discovered local records of species previously only known from further afield.

But some species are much more common than others. And the different ferns can be hard to tell apart unless you know exactly what to look for.

I'm not going to use this post as a fern ID primer, but I did want to introduce a fairly common and attractive group of ferns, the Shield Ferns, in the Lastreopsis genus. They are widespread and common in local rainforest, and to a lesser extent in wet forests dominated by eucalypts. They always catch my eye!

Perhaps the most common is the Creeping Shield Fern (Lastreopsis microsora), which can be seen on sloping banks in rainforest right along the escarpment, for example, between Mount Keira (Djeera) and Robertson's Lookout, or at the Illawarra Escarpment Management Track running south off Bulli Pass Road.

Here's a picture to give you the gist! But I must admit that identification of ferns to species level is challenging...

The ID challenge is definitely in operation with the Shield Ferns (aka Lastreopsis ferns). Three different Shield Fern species occur in the Illawarra region, and they are all somewhat similar-looking, with bi-pinnate fronds. They're also not a million miles away in appearance from some other ferns, including Bracken Fern (Pteridium esculentum) and Rainbow Fern (Calochlaena dubia), which is also often mistaken for Bracken Fern.

Close attention to the structure of the frond is important, and a good look at the reproductive parts (the sori, rounded or elongated brown-coloured patches that contain the fern's spores – their equivalent of seed) is invaluable in identification. 

Here's a picture of the sori of Creeping Shield Fern (Lastreopsis microsora), showing the placement of the sori along the frond lamina. Lastreopsis or Shield Ferns have small circular sori, as shown in the picture below. Unfortunately, ID does get a bit technical! But keep in mind that the almost-pestiferous Bracken Fern doesn't have circular sori – it has sori that round around the edges of margins of the fronds, more or less continuously. If you keep that tip in mind, you may be able to tell your Shield Ferns from your Bracken Ferns quite easily, as long as the sori are visible.  

Next time you take a wander in the woods or forest or rainforest, take a moment to observe the different ferns you see around you. You may be in the presence of three, five, eight or more different species of ferns. They can all eventually be identified by paying close attention to details such as the size and shape of their fronds, the colour or shape of scales growing on the fronds, or the shape and location of the spore-bearing sori on the underside of the leaves.

This might sound really complex and difficult, but it's basically nature's Sudoku: a way to keep us all thinking about, attending to and learning about the amazing biodiversity that's at our doorsteps. Happy fern learning!