Lewis & Short

ărista, ae, f. [perh. for acrista and akin to ācer, q. v., or perh. to aro, q. v.; cf. Germ. Aehre; Engl. ear (of corn); Germ. Ernte, harvest; Engl. earnest, fruit, pledge].

  1. I. The awn or beard of grain: arista, quae ut acus tenuis longa eminete glumā; proinde ut granitheca sit gluma, et apex arista, Varr. R. R. 1, 48; * Cic. Sen. 15, 51; Ov. H. 5, 111; id. Tr. 4, 1, 57.
  2. II. Meton. (pars pro toto).
    1. A. The ear itself: maturae aristae, Ov. F. 5, 357: pinguis arista, Verg. G. 1, 8; 1, 111; id. A. 7, 720.
      Also, an ear of spikenard, Ov. M. 15, 398.
      Hence,
      1. 2. Poet., summer: Post aliquot, mea regna videns, mirabor aristas, after some harvests, Verg. E. 1, 70: necdum decimas emensus aristas Aggrederis metuenda viris, having measured ten summers, Claud. IV. Cons. Hon. 371 (cf. at the next grass, for next summer, an expression still common in the north of England; so, seven years old at the next grass, Sylvester’s Dubartas; just fifteen, coming summer’s grass, Swift).
    2. B. Poet. transf.,
      1. 1. Of the hair of men, Pers. 3, 115.
      2. 2. Of the bones of fishes, Aus. Mos. 85; 119.
      3. 3. Of plants in gen., Val. Fl. 6, 365.