From speiro; something sown, i.e. Seed (including the male "sperm"); by implication, offspring; specially, a remnant (figuratively, as if kept over for planting) -- issue, seed.
KJV: Which indeed is the least of all seeds: but when it is grown, it is the greatest among herbs, and becometh a tree, so that the birds of the air come and lodge in the branches thereof.
NASB: and this is smaller than all other seeds, but when it is full grown, it is larger than the garden plants and becomes a tree, so that THE BIRDS OF THE AIR come and NEST IN ITS BRANCHES."