Yes, HACKBERRIES is a Scrabble word!

Letter values in Scrabble US: H 4, A 1, C 3, K 5, B 3, E 1, R 1, R 1, I 1, E 1, S 1.

Is it a valid word?

HACKBERRIES is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

any of various trees of the genus Celtis having inconspicuous flowers and small berrylike fruits
small edible dark purple to black berry with large pits; southern United States

Also: nettle tree.