i.e. Most of them; or herbs and trees of all sorts, as appears from Exodus 10:12,15. See Poole on "Exodus 9:6".
Related Commentaries of Exodus 9:25
Exodus 9:25
25 And the hail smote throughout all the land of Egypt all that was in the field, both man and beast; and the hail smote every herb of the field, and brake every tree of the field.