Amr bin Ubayd relates from al-Hasan (may Allah have mercy on him) that the Messenger of Allah (peace and blessings be upon him) "prescribed zakah only on ten things: camels, cattle, sheep and goats, gold, silver, wheat, barley, dates and raisins."
Ibn Uyaynah (may Allah have mercy on him) said: I think he said: and sorghum (dhurah).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7480