Poison has been drilled into trees in Watford, in a suspected attempt to kill them off.
Trees growing on the footpath between rear gardens of Oak Green and houses on Wadham Road, in Abbots Langley, have been found with holes drilled into the trunks.
Hertfordshire Constabulary believe that a toxin of some kind has been inserted into the holes in an effort to cause damage to the trees.
Councillor Chris Lloyd, lead member for leisure and community, said: “There are over 750 Tree Preservation Orders in place across the District and the Council will continue to protect our most valuable trees”
The criminal damage is likely to be detrimental to their long term health.
As the trees were tampered with without consent of the council and they are protected under the TPO legislation, successful prosecution can lead to fines of up to £20,000.