Northern Tablelands MP Adam Marshall was a special guest and opened the group's new tunnel house at its Mann Street premises.

"The tunnel doubles the capacity of the nursery and there was a good crowd of onlookers when it was opened by Adam at 10am," group member Kerry Steller said.

"The sun came out for a day packed with informative and fun activities."

Group president David Steller and Struan Ferguson from Southern New England Land Care spoke of the great asset the new tunnel house would bring to the region.

It was partially funded by the Koala Strategy Northern Partnerships, Biodiversity and Conservation, Department of Climate Change, Energy, the Environment and Water.

Attendees voted on a name for the new tunnel house on the day and "Michaeliana" was voted highest.

Eucalyptus michaeliana (the Hillgrove gum) is a local eucalypt species that grows well in the region.

"People flocked to the workshops on propagation by wholesale team leader Sam Arandale-Bioletti, plant identification and plants to attract birds by Peter Metcalfe, and koalas with Dave Carr," Ms Steller said.

Informative talks were delivered by Dr Andrew Thornhill on mosses and bryophytes, Dr Jane Andrews on eucalypts, Penelope Sinclair on mixing natives with exotics in your garden and Dr Jane Pickard on walnuts and wattles.

Children were enriched with nature journalling and nature treasure hunting in the woodland with Ms Steller and Ann Haining.

"Beautiful plant print artworks by Emily Curtis, Shirley Tier and Lilian Creamer were on show and some are still available for sale," Ms Steller said.

Southern New England Landcare, Australian Plants Society and Northern Tablelands Wildlife Carers sat their displays under the watchful eye of the Giant Koala who helped give away free trees to those in attendance.

Music was provided by Steve Tafra, Sue Metcalfe and the Cello Choir and the Recorder group.

"They provided a lovely ambience as people sat or wandered around the greenery in the nursery and undertook tours of the facility," Ms Steller said.

"We want to thank all our supporters who attended on the day.

"Having turned 40 years as a community not-for profit group and as the winner of the ARC Australia Day Awards for an Environment Group, the Tree Group is proud to show off some of the work we do in putting back into the community."