The Scottish Railway Preservation Society (SRPS), which runs trips across Scotland, said the problem was affecting nearly every route it used.
SRPS Railtours commercial director Roger Haynes said: “It is getting out of hand. There needs to be a drastic move to cut back foliage anywhere near lines.”
Two windows were smashed on an Inverness-bound SRPS train near Newburgh in Fife last month.
Glass shattered near passengers, including a baby, who escaped injury.
Last year, the steam locomotive Tornado suffered some £10,000 worth of damage on a ScotRail trip from Stirling to Inverness and Brora.
Graeme Bunker, Tornado’s operations director, said: “We often get both Tornado and its support coach scratched when they go out. Some of the worst we have had is on the Fife Circle.
“The lack of attention to lineside growth also removes some of the most spectacular scenery. The problem for many lines is they are in effect ‘green tunnels’.
“Whilst understanding Network Rail has many competing priorities, it is a disappointment that lineside vegetation is not more under control.”
A spokeswoman for the Belmond Royal Scotsman luxury train, whose Scottish trips cost passengers up to £7,500, said scratched carriages were “quite a common occurrence”.
ScotRail said a “handful” of its trains had been “slightly damaged”.
Network Rail said damage claims below £10,000 were rejected as “operational expenses”.
A spokesman for the ScotRail Alliance, which includes the track body, said: “We dedicate significant resources every summer to cutting back quick-growing vegetation.
“Lineside vegetation can obscure signals, become entangled in overhead power lines and obscure drivers’ sight lines. As a consequence we have prioritised our summer clearance works at locations were they will most improve safety.
“We receive very few compensation claims for damage caused by vegetation to engines and rolling stock.”