The avocado fruit does not ripen on the tree, but will fall off (and must be picked up) in a hard, "green" state, then it will ripen quickly on the ground, but depending of the amount of oil that it has the taste may be very different. Generally, the fruit is picked once it reaches a mature size, and will then ripen in a few days (faster if stored with other fruit such as bananas, because of the influence of ethylene gas). The fruit can be left on the tree until required, rather than picked and stored, but for commercial reasons it must be picked up as soon as possible. If the fruit stays on the tree for too long it will fall on to the ground. While dozens of cultivars exist, two are particularly commonly available, 'Hass' (commonly misspelled 'Haas') and 'Florida'. The former is the most common cultivar, with a dark rippled skin, and rich, creamy flesh, accounting for more than 80% of the crop grown in California. All Hass avacado trees are related to a single "Mother Tree" that was purchased as a seedling by a mail carrier named Rudolph Hass. He purchased the tree as a seedling from A.R. Rideout of Whittier,California, in 1926. Hass planted the seedling in his front yard in La Habra Heights, California, and patented the tree in 1935. All Hass avacados can be traced back to grafts made from that tree. The "Mother Tree" died of root rot in 2002. There are several other cultivars related to 'Hass', including 'Bacon', 'Fuerte' (pictured), 'Gwen', 'Pinkerton', 'Reed', and 'Zutano'. The cultivar 'Florida', grown mostly outside of California, is larger and rounder, with a smooth, medium-green skin, and a less fatty, firmer and fibrous flesh. These are occasionally marketed as low-calorie avocados.