Invasive plants including rhododendrons and Himalayan balsam are fast-spreading species which suffocate native trees and flowers, and are a threat to the richness of species in UK woodlands, the nature charity said.
It spent £70,000 clearing rhododendron from one woodland alone last year, Rhododendron Wood in Kentisbeare, Devon, more than £31,000 on the problem in Kingsettle Wood in Shaftesbury, Dorset, and £20,000 at Penn and Common Woods in Buckinghamshire.
Clearing these plants often means painstaking work or using heavy machinery, and needs years of follow-up work to keep at bay.
Andy Sharkey, the Woodland Trust’s head of estate, said: “Invasive plants remain a constant threat to the wildlife value of our woods and to woods in general.
“This is truly an issue that requires all landowners to look to work together and continue with their efforts.”
Rhododendron comes from the Mediterranean, Asia and China and was introduced in the 18th century when Victorian country estates planted it for ornamental reasons, but it spreads rapidly in the wild where it is an offence to plant it or cause it to grow.
Himalayan balsam, another common invader, was introduced to Britain in 1839 for its pink slipper-shaped flowers. It spreads quickly by forming dense colonies, and shades out and kills native vegetation.