What is the difference between a grove and an orchard?

A grove is a stand of fruit or nut trees without underbush.
An orchard is a planting of fruit or nut trees planted for the purpose of harvesting.
All orchards are decideous trees and all groves are evergreen trees.
http://www.wikianswers.com

That's a bit contradictory.

If a grove is "a stand of fruit or nut trees", it is not likely they are going to be evergreens.

Let's stay away from using other "ask" sites for references. They're just doing the same thing we're doing, only not so well. :)

A grove can be any sort of tree, whereas an orchard is grown for the fruit. While 'grove' can be used for a 'small orchard',
https://en.wikipedia.org/wiki/Grove_%28nature%29
groves are often associated with Druids (but please ignore most of the rubbish 'recorded' by J. Caesar & Co - just look what the (later in the case of Christian) Romans said about Jewish and Christian rituals before you believe them about Druids), and other sacred or educational (see Ancient Greeks) establishments.
https://en.wikipedia.org/wiki/Sacred_grove
and
https://en.wikipedia.org/wiki/Academia
(passim)
It should be noted that olives, despite being grown for their fruit, live in groves for the most part. They can live in orchards, but when have you ever seen a restaurant called 'The Olive Orchard'?

Sudden thought: There appear to be groves of macadamia nut trees, but no-one's done a skit on 'The Groves of Academe' yet using 'The Groves of Macadame' as a title. Could be set in a Scottish university or college. I'm not going to write it, but I would like an acknowledgement when you do.
https://en.wikipedia.org/wiki/The_Groves_of_Academe