The researchers, Robert Colautti and Spencer Barrett, found purple loosestrife produced fewer fruits the farther away it was from its original habitat. That indicated that the plants' differences were adapted to their environments. Northern purple loosestrife has to deal with a shorter growing season, so it blooms early in the spring to take advantage of as much time as possible. Compared to southern loosestrife grown in the north, it can produce up to 37 times as many fruits. But because it blooms later, southern loosestrife can grow bigger. In the southern U.S., where the growing season is long, southern-adapted loosestrife makes nine times as many fruits as northern-adapted loosestrife.