The avocado is an amazing fruit. It grows on a tree and comes to maturity, reaches certain oil content and a stage at which it will ripen, but it does not ripen on the tree. It needs to be removed from the tree before it will soften. If the fruit is removed before it has reached maturity it will not soften, and will remain rubbery and inedible. One of the problems is that the fruit will hang on the tree for an extended period of time and it is hard to know when they are mature. Avocados are not like apricots where you have about 2 weeks to get the fruit off before it falls off. As the fruit stays on the tree in gradually develops more and more oil content and has a richer flavor.
If the fruit stays on the tree too long, the oil can develop and almost rancid flavor, however. So it is good to know when the best, acceptable flavor is. Avocado varieties fall into general seasonal periods when they are mature, such as Fuerte' and ‘Bacon” in winter, ‘Hass' in spring/summer, ‘Lamb-Hass' in summer/fall.
To assess maturity, take an unripe stage cut the fruit in half. Look at the seed coat. If the seed coat (the covering of the seed that separates it from the flesh) is white and thick, it is definitely not ready to pick. If it is whitish brown and getting thinner, then if you are desperate, you can try ripening the fruit and taste. If the seed coat is thin and brown, then usually this will mean that the fruit is ready to pick. If the seed has germinated already in the fruit then normally the fruit is over the hill. Some green skin varieties skin will begin to crack when the fruit are very mature on the tree. This will tell you when you have reached the end of the useful tree life of the fruit.
For ripening, pick the fruit and without any help, the fruit will typically be ripe in 7 to 10 days. If you want to speed things along a bit you can take 3 or 4 avocados and place them in a loosely closed paper bag with 2 – 3 Red or Golden Delicious apples or ripe kiwifruit. The purpose of the apples or kiwifruit is that these fruit produce a natural plant hormone, ethylene that will help stimulate the avocado to produce its own ethylene. Apples and kiwifruit are known to produce lots of ethylene. The Delicious apples are varieties that produce more ethylene than other apple varieties. You can keep them even after they are shriveled and they will be producing ethylene. Don't use a plastic bag unless you keep it opened since the fruit need to breathe during this process. Just keep the fruit on your kitchen counter or in a warm place. 68F is the ideal temperature. Lower and higher temperatures both actually slow the process.
