A farmer wants to compare the tastiness and juiciness of tomatoes grown with three amounts of a new fertilizer: none, half the recommended amount, and the full recommended amount. The farmer allocates 6 tomato plants to receive each amount of fertilizer, assigning them at random. To obtain enough plants for the experiment the farmer has to purchase plants from two different garden centers. The farmer then randomly assigns the plants from each garden center to all three fertilizer treatments. Is the experiment blocked? Is that a good idea?