Erm. That’s essentialist/teleological thinking through and through. This is a remarkably apt quote in showing up how madly you misrepresent essentialism and teleology. She may not have understood how deeply Aristotelian her points about the tree were in 1961, but the fact remains.
…So it turns out that late in her life, in Natural Goodness, she explicitly recognizes this fact.
Anscombe writes, ‘[G]etting one another to do things without the application of physical force is a necessity for human life, and that far beyond what could be secured by . . . other means.’[18] Anscombe is pointing here to what she has elsewhere called an ‘Aristotelian necessity’: that which is necessary because and in so far as good hangs on it.[19] We invoke the same idea when we say that it is necessary for plants to have water, for birds to build nests, for wolves to hunt in packs, and for lionesses to teach their cubs to kill. These ‘Aristotelian necessities’ depend on what the particular species of plants and animals need, on their natural habitat, and the ways of making out that are in their repertoire. These things together determine what it is for members of a particular species to be as they should be, and to do that which they should do.[20] And for all the enormous differences between the life of humans and that of plants or animals, we can see that human defects and excellences are similarly related to what human beings are and what they do. We do not need to be able to dive like gannets, nor to see in the dark like owls; but our memory and concentration must be such as to allow us to learn language, and our sight such that we can recognize faces at a glance; while, like lionesses, human parents are defective if they do not teach their young the skills that they need to survive.
(Philippa Foot, Natural Goodness, 15)
She goes on to draw heavily on Michael Thompson’s idea of “Aristotelian categoricals.” In Natural Goodness Foot appeals to primary or secondary sources on Aristotle in seven of her footnotes, and she appeal to Aquinas in four footnotes while drawing on him heavily in parts of her text.
So Anscombe got Foot straightened out eventually, at least by the time she was 80. 
I’m sure she would have profited greatly from Peter Simpson’s book, Goodness and Nature: A Defense of Ethical Naturalism and a Critique of its Opponents. I wonder if Simpson knows that she came around.