[ He pauses briefly in his digging to watch him sign and then resumes, scooping up more soil. ]

They produce a substance known as juglone, which is toxic to many plants, and can cause allergic reactions in humans. The juglone seeps into the soil and susceptible plants turn yellow, wilt, and sometimes die.

[ Fun facts with Professor Asuka! Okay, that probably wasn't very fun, but it was factual. It's a good thing he tried to give the walnut to Dextera instead of handing it over to Dave to plant in the garden like he originally intended. ]