The challenge can be taken on with any paper and pen. The pack exists for those who want the gesture to be complete and meaningful. You write the letters with the plantable pencil — when you finish the challenge, you plant it, and when it grows it will remind you why you did it. Inside each envelope goes a plantable card, so that the person who receives your words also takes away something alive. Because the gesture doesn’t end when the letter is sent — it keeps growing in each person who receives it, and beyond.