Adaptation

Although Psidium guajava grows best in soil with a pH between 5 and 7, it has adapted to accommodate a ph between 4.5 and 9.4.  It has adapted to accommodate semi-salt water as long as the plant has good drainage. Also has developed a good system of water storage so it can survive times of drought, though it does best with regular watering. Because of this it can thrive in both humid and dry climates. It can also withstand a brief exposure to freezing temperatures ( below 0°C (32°F)), however it may loose a little foliage. Fruit is usually bared better in areas with a defined cooler season, though they can only take so much frost.

It's because of all the water and sun they recieve in tropical areas that the P. guajava grows like a weed.