200K Christmas trees used to fight invasive carp — and the RBG needs more

The gatekeepers of vital Hamilton waterways are coming from living rooms across the city, where they were once covered in ornaments and tinsel.

The Gardens needs thousands more donated to rebuild vital natural barriers

The Royal Botanical Gardens is using donated Christmas trees to build and maintain a barrier that keeps invasive carp out of some of Hamilton's waterways. (Royal Botanical Gardens)

The gatekeepers of vital Hamilton waterways are coming from living rooms across the city, where they were once covered in ornaments and tinsel.

For almost 20 years, the Royal Botanical Gardens has been using donated Christmas trees to form natural barriers at the mouth of Grindstone Creek and Cootes Paradise.

It's all to keep out the non-native common carp, an invasive species that destroys natural habitats and creek beds in the area. The barriers also prevent sewage and sediment from seeping into Cootes.

This year — largely thanks to high water levels that plagued the city through most of 2017 — the RBG is searching for 3,200 donated trees to help rebuild its cache and keep creek beds safe.

"It's quite a thing when you think about it – they all used to be in a location as Christmas trees," said Tys Theijsmeijer, the head of natural areas with the RBG.

The barrier is also used to keep sediment and sewage out of Cootes Paradise. (Royal Botanical Gardens)

Over the years, about 200,000 local trees have been donated for the longstanding project, Theijsmeijer said. It's kind of like playing beaver, but with an environmental focus.

But why Christmas trees? Theijsmeijer says for one, it's a natural solution to a recurring problem. Secondly, the trees are more buoyant than metal or plastics, which keep them from sinking into the creek beds.

"The land we put them on is really soft … if you put anything too heavy on it, it just disappears," he said.

The trees then slowly decompose over time (as anything natural kept in water would) and have to be replaced. This year, more have to be replaced than normal, thanks to the flooding the city experienced for several months, which kept water levels significantly higher than normal.

Floodwaters damaged the Christmas tree barrier this year. (Royal Botanical Gardens)

The barriers spent a significant amount of time completely underwater, Theijsmeijer says, which led to a higher rate of decomposition.

Anyone who is looking to donate a tree can do so until Jan. 12 at two locations: 1200 Spring Gardens Rd in Burlington, and 335 Longwood Rd N. at Princess Point in Hamilton.

Just make sure your tree doesn't have any decorations on it.

"You'd be surprised," Theijsmeijer said with a laugh.