משנה על נדרים 7:1

Five species [of grains] are subject to [the law of] hallah: wheat, barley, spelt, oats and rye. These are subject to hallah, and [dough made from different types of these grains] are accounted together one with another [as one quantity]. And their “new” [harvest] is prohibited prior to Pesah, and [they are subject] to [the prohibition of] reaping prior to the Omer. If they took root prior to the Omer, the omer permits them. If not, they are prohibited until the next Omer has come.

As for untithed produce, what grows from it is permissible if of a kind whose seed disintegrates [in the soil]. But if of a kind whose seed does not disintegrate, then even what grows from plants which grew out of it are forbidden. Which is the kind whose seed does not disintegrate? Like luf, garlic and onions. Rabbi Judah says: garlic is like barley.

As for untithed produce, what grows from it is permissible if of a kind whose seed disintegrates [in the soil]. But if of a kind whose seed does not disintegrate, then even what grows from plants which grew out of it are forbidden. Which is the kind whose seed does not disintegrate? Like luf, garlic and onions. Rabbi Judah says: garlic is like barley.