An Etymological Dictionary of the German Language/Lärche
Lärche, f., ‘larch,’ from the equiv. MidHG. lęrche, larche; OHG. *larihha is by chance not recorded, but Lat. larix (acc. larĭcem, comp. Kelch from Lat. calicem) necessarily leads to OHG. *larik, and then by permutation and mutation to *lęrihha. The permutation of k to ch, and the fact that the word is based on a Lat. term pronounced larikem (E. larch), point to a very early adoption; comp. Kelch.