Pine trees and fertility

“Weed it & weep” (February 12), on invasive plant pests, made sobering reading. It also highlighted the conundrum that makes pine trees both a blessing and a blight. They are a blessing because they provide a useful and valuable product while also absorbing carbon dioxide and creating a vast, fast-growing carbon sink. They are a blight for a number of reasons, including their weediness, which poses a constant threat to native habitats.

But their weediness could be controlled by preventing them growing in the first place. If plantation pine trees didn’t produce viable seeds, they would not become problem weeds.

Selective breeding for desirable qualities is the mainstay of our primary industries. In forestry, it means trees that grow faster and straighter, with increased wood density and disease resistance. The best trees are propagated by cuttings or tissue culture, so many forests are made up of clones.

Breeding and selection might eventually find a sterile pine tree, but it would be much quicker and simpler to genetically modify pine cells so that the subsequent clones grow into trees that are sterile, without altering their other desirable qualities. Being sterile, such a tree could not pass on its genetic alteration to other plants.

But gene