Fruits which fell off a tree:
All fruits which have fallen off a tree on Shabbos are forbidden to be eaten until after Shabbos and are therefore Muktzah. [Furthermore, even if there is doubt as to if the fruits fell on Shabbos or beforehand it is forbidden.]
Are vegetables which detached from the ground on Shabbos forbidden to be eaten?
Yes. Hence they are Muktzah.
 Michaber 322/3
 The reason for this is due to a decree one may come to pluck a fruit from the tree on Shabbos. Alternatively it is because the fruit is Muktzah as one did not have it in mind from before Shabbos. [M”B 322/7]
 Ketzos Hashulchan 146/23 from Peri Megadim, Upashut.
 M”B 322/5; brought in Ketzos Hashulchan 146/23
 M”B 322/6 in name of Peri Megadim