I just finished the low poly rocket tutorial and it was so much fun. Loved the design for this tutorial so came to give it a shot. I am at the part where you delete all the branches to begin crafting leaves, but when I invert and delete vertices I am left with a ton of particles. Any ideas?
Looks like you may have leaves turned on when you created your tree but no object assigned as your leaves.
In the Outliner , Top right of the screen, You have the names of your trees. Your currently working on Spruce B.000, just to the left of the name you have a small arrow, click it and everything that makes up your tree will be displayed. See if you have anything named leaves, select it if you do and delete it.
Hope this solves your problem.
Help yourself to a cookie.
Adrian is exactly right. While recording this course I realized that leaves are emitted from small planes that a generated by the sapling addon. Disabling leaves in the addon will eliminate this result OR deleting the planes in the outliner as described by Adrian will solve it after the fact.