River Witham weed growth cancels Boston Rowing Marathon event

Weeds in the River Witham in Boston in 2022.

Organisers of Boston's Rowing Marathon say this year's event has been cancelled due to the "continued" seasonal build up of river weeds.

The 30.6-mile (49.2 km) race from Lincoln to Boston along the River Witham is traditionally held each year on the third Sunday of September.

Boston Rowing Club said it was now looking at the possibility of moving the event to May 2024.

The Canal and River Trust (CRT) said river weed had been a "real challenge".

In a Facebook post, the rowing club explained that "due to the continued build-up of weed along the River Witham between August and September/October we have made the decision to not run in September".

The club added: "We are looking for a suitable date in 2024. Maybe early May, not ideal we know.

"We are really sorry about this."

Last September's river marathon was also cancelled due to a thick covering of vegetation on the water.

'Perennial battle'

A CRT spokesperson said it was a "real shame" the rowing club had decided to cancel but they shared the group's frustrations.

They said a weed boat was working on the river five days a week and they were also working with the Environment Agency.

"We share their frustrations at what has become a perennial battle with weed on the river.

"The scale of the problem in recent years has been a real challenge with warm weather and nutrient rich water providing ideal growing conditions for fast-growing invasive and non-native invasive weed," the spokesperson added.

The non-native fast-growing Azolla weed was mixed in with duckweed and is up to 4in (10cm) thick in places

In recent years, the Witham has been carpeted in greenery up to 4in (10cm) thick in places, made up of non-native fast-growing Azolla weed and duckweed.

Azolla can reduce oxygen in the water and harm fish and other aquatic life and each plant can double in size every three days, making waterways unnavigable for smaller boats.

Boston Rowing Marathon was first held in 1946.