It is grown in a pet's garden from the Flowering Cactus Tree Seed, which is the reward for collecting all five plants in the Potted Cacti Collection. After planting, it will take 72 hours for the tree to reach maturity. Afterward, the tree will begin producing fruit, one fruit at a time, randomly. A pet can have up to three total Cactus Flower Fruit on the tree at once, unless you have the Fruit Fairy, in which case you will produce up to four.