Forests carpeted with bluebells are one of the most welcome sights of the Scottish spring, but could become just a memory unless urgent action is taken against invasive alien plant species which are choking the Scottish countryside, according to conservationists.

Now environmental charities are calling on the public to become "rhododendron bashers" to save the bluebell by taking on the plant that is turning once biodiverse Scottish woodlands into barren thickets.

Rhododendron ponticum is an invasive species, introduced into gardens as an ornamental shrub and in the countryside as cover for pheasant and game. Perfectly suited to the climate of the west of Scotland, it covers the forest in a thick, impenetrable layer of green foliage beneath which nothing can grow, including bluebells.

Graeme Walker, Scottish Natural Heritage Area officer for Ayrshire and Arran, said: "Once the rhododendron takes over, you can say goodbye to bluebells, it simply chokes them out. The only chance we have of winning against it is by direct action."

Once the rhododendron has taken over, the combination of toxic leaves it drops and the shade it casts makes life impossible for both flora and fauna. Conservationists are currently spreading bluebell bulbs around Scotland as the native form is under threat from the Spanish variety, but the rhododendron could knock both out of the ecosystem.

Steven Mason, a National Trust of Scotland countryside ranger, is leading a "rhododendron bash" as part of the Arran Wildlife Festival later this month, in the hope that the public will be inspired to start their own groups across Scotland.

He said: "There needs to be a higher priority on combating invasive species in general, because there is not a high enough consideration of the damage they can do to habitats. It would be very good if there was local groups involved. There is a role for government, but it's something that the public need to get involved in it."

He added: "The longer we leave it, the bigger the cost and the damage to habitats will be."

Roy Sexton, a lecturer from Bridge of Allan, has volunteered for local rhododendron clearing schemes in Stirling and around Scotland. One of his expeditions was to an island in the middle of Loch Lomond, meant as a sanctuary for the endangered capercaillie. The island was so overrun by the invasive plant species that the birds' food, mostly young shoots and berries, could not survive.

He said: "One of the good things about rhododendron is that it does not leave a strong seed bank in the soil. Once you've got rid of it, you don't get any more seedlings come up. I've seen woodland that has been cleared and really benefited from it; this is a battle that can be won."

All prospective rhododendron-bashing groups need are tools to chop the wood and herbicide to paint the stumps so they don't grow back.

However, Gordon Patterson, of Forestry Commission Scotland, advised people to seek landowners' permission before taking any action.

Landowners and community groups can also seek funding from the Scottish rural development plan to take action against rhododendrons.