alligator-pear avocado avocado-pear black butter-pear climacteric-fruit cultivar egg-shaped fertility-fruit firm flesh food fruit Fuerte-variety green guacamole Hass-variety healthy large-berry large-seed nutritious ovate pear-shaped pebbled skin perennials persea-americana ripe rough section smooth soft tree wrinkled cut alligator pear avocado pear butter pear climacteric fruit fertility fruit Hass variety large berry large seed persea americana pebbled-skin kernel seed