Most green thumbs need only a small patch of dirt in the back yard to satisfy the urge to grow.

But for Norma Gillespie, who enjoys watching heritage trees make their way through the four seasons, a bigger chunk of land is required.

She is a member of the Riverview Horticultural Society, an organization dedicated to preserving the land and trees surrounding the Riverview Hospital site.

“It is like a 244-acre garden,” she said with the same pride as someone who tends to lettuce and tomatoes in her back yard. “It is one of the finer collection of trees in Canada as far as our society is concerned. It is the best in the Pacific northwest.”

On Sunday, Gillespie will be showing off the site on one of the society’s regular guided tree tours. Members of the Port Coquitlam Heritage and Cultural Society will also be in attendance to see the heritage buildings on the site as well as the historic arboretum.

Two separate tours will be held and, for those interested, a bus has been rented for the trip so participants can see more of the property.

Gillespie said that many people who live in the Tri-Cities have a long connection to the Riverview grounds.

“It has been here for so long,” she said. “So many people who lived in PoCo worked in Riverview.”

But for tree enthusiasts, Gillespie said the tour will be paying particular attention to the catalpa trees, which are in bloom this time of year.

“That is the great thing about having these walks,” she said. “Depending on the time of year, there is always something special going on.”

The Riverview Horticultural Society has been holding tree walks regularly for close to 16 years. In that time, more than 2,000 trees have been identified and tagged on the property, which goes from the north side of the Lougheed Highway up to Mariner Way.

Gillespie said a city arbourist usually comes along for the tours and answers questions people may have about the trees and their history.

• Those interested in attending this weekend’s guided tree tour with Norma Gillespie should meet in front of the Henry Esson Young building at 1 p.m. on Sunday. For more information about the Riverview Horticultural Society, go to www.rhcs.org.

gmckenna@tricitynews.com