Cashews are a tropical plant that produces an apple-like fruit and a nut that grows out of each fruit. The apple, which starts out yellow and becomes red when ripe, is edible and high in vitamin C, but it's reportedly not that tasty. Each fruit produces only one nut. If you've noticed that you can't buy unshelled cashews, there's a reason: the shells are toxic — they contain the same chemical as poison ivy and can cause rashes.