"落叶松属植物" can be translated into English as "plants of the genus Larix" or simply "Larix species".
Here, "Larix" is the genus name for larch trees (落叶松属 in Chinese), and "species" refers to the different kinds within this genus. If you want to be more specific about referring to the plants collectively without listing individual species, "plants of the genus Larix" is a suitable expression.