'Mustard' in the Bible

It is like unto a grain of mustard seed, which a man took, and cast into his own garden; and it grew, and became a tree; and the birds of the heaven lodged in the branches thereof.

And the Lord said, If ye had faith as a grain of mustard seed, ye would say unto this sycamine tree, Be thou rooted up, and be thou planted in the sea; and it would obey you.