A gift given by the Ringmaster to those that went into hell to rescue carnival members from vampires, the phoenix fruit is a miniature version of a tree from her homeland. They resemble small citrus trees, with fruits that will grow to be yellow, orange, or red depending on the particular breed. The ones given out to carnival members will be random in colour. (You can choose!) The trees take only 2-3 weeks to grow to full maturity, but the seeds cannot be transplanted to create new trees without magical aid. When the fruits become ripe, they begin to faintly glow, as if with inner candle light.
Yellow fruits have regenerative properties. Eating them will cause injuries to heal faster, and will help to eradicate illness. Orange fruits stimulate the mind, allowing one to remain awake and attentive far longer than normal, though constant use of them may have detrimental effects. Red fruits cause an experience similar to an intense adrenaline surge when eaten, allowing one to perform physical and spiritual feats that would usually be beyond them.
When fully grown, each plant will sprout roughly one new fruit every day or two. They will never get much larger than the miniature size indicated.
This is what happens when Steven Universe licks a fertile phoenix fruit seed and gives the lemons sentience.