SO WHAT is a native grass and what is an exotic?

It's a question many of us ask when weeding, bushwalking, or just trying to fathom the vast array of grasses that cover our great Australian landscape.

Many questions were answered on Wednesday when experts Margaret Elliot and Penny Watsford put their knowledge to the test at Fingal Head for a workshop.

The hands-on session reflected the content of their book "Grasses of Subtropical eastern Australia," an introductory field guide to common grasses both native and introduced.

Interested people joined Fingal Coastcare on a two-hour journey starting from the Coastcare Nursery and pausing for lunch on the headland.

"It was a fascinating journey," said president of Fingal Head Coastcare Kay Bolton.

"We often wonder about what grasses are native and what is introduced.

"This was a very informative session."

The book includes a CD-ROM and illustrations with both formal names and the common names for grasses, as well as their height, texture and specific features.

It's the third book in the series.

"Frustrated by the other grass books available, we decided to produce one ourselves," the authors said.

That one became three.

The first book was "Grasses of the Tweed Valley."