1$ plant library: https://blendermarket.com/products/plant-models-vol-60-blender?ref=311
/>botaniq: https://blendermarket.com/products/botaniq-trees?ref=311
/>nisaga: https://blendermarket.com/products/nisarga-add-on?ref=311
/>
free models:
https://blendereverything.com/category/free-models/