I live in the Bronx and work in Manhattan. You're obviously not going to find aloe growing in central park, but there are at least half a dozen other plants there that can be used to treat minor burns and other skin conditions. E.g. plantago, jewelweed, witch hazel, etc.

According to at least one prominent American zen buddhist, the secret to the good life is, "stay together, learn the flowers, go light." This isn't some sort of metaphor, go outside.