Jacquie Loughrey, from the Pink Ladies, expressed disbelief that flower-filled planters and a park bench that were only installed on Monday had been targeted.
The fixtures were placed at the iconic Bogside tourist attraction as part of a joint Pink Ladies and Triax campaign to raise awareness of the health dangers posed by pesticides.
At some stage last night vandals overturned the planters, moved the park bench and scrawled 'This wall is for the people!!! We won't be silenced!!!' on Free Derry Wall.
Ms. Loughrey said: "This greatly saddens the Pink Ladies cancer support group that works tirelessly to support the whole community after a cancer diagnosis. This campaign is an attempt to highlight the dangers of using pesticides/weed killer and the link to a cancer called Non-Hodgkin Lymphoma.
"It’s a joint project with an environmental community group Triax Neighbourhood Management Team to encourage more planting of wildflowers/bulbs to bring back our bee population and make the community area more attractive to live in.
"The flowers were an indication of what could be done in the Bogside and Brandywell area without continually spraying weed killer that is a threat to our health and the bee population."
The flower display and seating area at the front of the wall was part of the Pesticide Free Derry Campaign that was launched on Monday. It was intended as a temporary feature.
Sinn Féin Councillor Patricia Logue said: “Local people are shocked that anyone would carry out this act of vandalism on this project. It consisted of a wooden bench and flower arrangements. It was a novel idea and brought a bit of colour to the front of Free Derry Wall.
"I know it has been popular with residents and tourists to the area over the past few days. That anyone would contemplate doing this has left many people scratching their heads in disbelief. Hopefully this can be replaced as soon as possible."
On the Pesticide Free Derry campaign Ms. Loughrey said: “In May 2019 I worked with Councillor Patricia Logue to secure the passing of a motion by Derry City & Strabane District Council, stating: 'That this Council recognises the health and environmental risks associated with Glyphosate, which the World Health Organisation has upgraded to 'probably carcinogenic in humans'."
The motion called on DC&SDC to stop using 'all products containing glyphosate in this Council district, in favour of a more environmentally friendly product.'
Ms. Loughrey said: "We have written to the Chief Executives of the NIHE and the Education Authority, together with the Chair of the Health and Education committees, asking that they
ensure that their organisations do likewise."
An awareness campaign for residents, schools, gardeners, landlords and statutory agencies is in preparation.
"In the weeks and months to come we will be rolling out this work and we are only too willing to meet with anyone who would like to discuss this issue," said Ms. Loughrey.