Reference for Terumot 9:6

הַטֶּבֶל, גִּדּוּלָיו מֻתָּרִין בְּדָבָר שֶׁזַּרְעוֹ כָלֶה. אֲבָל בְּדָבָר שֶׁאֵין זַרְעוֹ כָלֶה, גִּדּוּלֵי גִדּוּלִין, אֲסוּרִין. אֵיזֶהוּ דָבָר שֶׁאֵין זַרְעוֹ כָלֶה, כְּגוֹן הַלּוּף וְהַשּׁוּם וְהַבְּצָלִים. רַבִּי יְהוּדָה אוֹמֵר, הַשּׁוּם, כַּשְּׂעוֹרִים:

Non-tithed produce, its growths are permissible in a kind whose seed disintegrates. But in a kind whose seed does not disintegrate, [even] the growths of its growths are forbidden. Which is a kind whose seed does not disintegrate? For instance, <i>Luf</i> [plant], garlic, and onions. Rabbi Yehudah says: onions are like barley.

Jastrow