When it’s time to say goodbye to the old holiday tree, the transfer station won’t be accepting them this season, according to Jen Fascitelli, administrative manager for the Department of Public Works.

Instead, residents are being asked to bring their trees on Jan. 6 and Jan. 13, from 10 to 2 each day, to Merwin Meadows, where workers from the Mianus chapter of Trout Unlimited will take them to stabilize streambeds and reduce erosion.

“We’re doing it as a cooperative thing — it helps us out and it helps them out,” Fascitelli said.

The concept is called eco-cycling. No synthetic trees or trees with tinsel or flocking will be accepted. There is no charge for the drop-off, but there is a suggested $10 donation, said Jeff Yates of New Milford, conservation chairman for the Mianus chapter.

Volunteers from the Mianus chapter will turn the Christmas trees into important habitat for wild trout in the Norwalk River. They create refuge habitat for juvenile trout and other aquatic life, the organization said in a flyer going around town.

Essentially, the trees are anchored to the banks of the river to prevent erosion.

“The Mianus chapter has been working on the Norwalk River for a good 20 years now, to protect the wild spawning trout in the river,” Yates said. “It is one of the healthiest streams in lower Fairfield County and has wildly reproducing trout in the spring. Our mission is to improve the water quality and habitat.”

The Christmas trees are made into what is called a conifer revetment, a structure designed to stabilize eroding stream beds, and to provide deeper pool habitat for trout and other aquatic life like eels and even insects.

“It works simply. The branches of the pine trees are so thick that when the river floods, as the water flows through the branches, they slow the speed of the current down and cause the sediments to settle to the bottom. Over time, it traps the sediment,” Yates said.

Eventually, this builds a new riverbank that is more stable and less prone to erosion and creates a better habitat for the trout.

“We put the trees in where the river has gotten too wide,” Yates said.

The river gets wide because of storm water runoff. It creates flash flooding that erodes the riverbanks.

“So we build a new riverbank to narrow that channel,” Yates said.

This is second year the Mianus chapter has partnered with the town of Wilton to collect trees. Last year, 400 trees were collected from Wilton and surrounding towns, he said.

The work has paid off. The water quality over the past 20 years has improved greatly and there is more wildlife, he said.

“You may see a mink looking for crayfish or small minnows. Even osprey come up the river to feed,” Yates said. “By taking care of the river, we’ve improved the base of that food web for that entire ecosystem.”