They can reach heights of 20-25 feet but can be maintained at around ten feet. Guavas even fruit well in containers. They are evergreen or deciduous, depending on the severity of the winter. During hard freezes, there may be some die-back of the upper branches, but new growth will quickly replace the limbs lost.
Fragrant and showy flowers appear in early spring.
I 've experimented with different materials and I'm currently using little bags I made from a product called floating row cover. It allows light, water and air to reach the developing fruit, while keeping out insects. I've also used plastic sandwich baggies, but if they are exposed to direct sun the fruit will burn on that side, causing a large brown sunscald on the skin.
For plastic baggies, I slip the baggie over the green fruit, and lightly secure with a twist-tie. When the fruit ripens, it loosens from the stem and drops into the baggie. The weight pulls the baggie off the stem and it drops to the ground. During guava season I simply go out each day and pick up the fallen fruits, free of fruit fly damage. The fabric bags don't slip from the stem as easily so I usually have to manually remove them when the fruit is ripe.
Young stems are four-sided, while older trunks and branches have an attractive smooth bark that flakes off in patches.