The traditional European or "pear shaped" pears are harvested unripe or green off of the tree and allowed to ripen later. The Asian type pears - or "apple pears" are harvested like (you guessed it) apples - ripe off the tree. The Asian pears are round like apples, so this is easy to remember how to harvest them.
Most of the Asian pears are originally from Japan (those of Chinese origin are more pear shaped and have green skin when ripe). The Japanese cultivars' round fruit is either smooth or russetted and ripen from July to October. They are ready to harvest when they change color and become sweet and tasty - ripe off the tree.
European pear cultivars vary in shape, juiciness, texture and skin color. They are harvested before they are fully ripe - at a firm stage - when the color of the fruit changes from a deep green to a lighter green and the small spots (lenticels) on the skin change from white to brown. If European pears are left on the tree to ripen, they ripen from the inside out, so the center is mushy when the outside is ready to eat. Stone cells also develop in the fruit and the texture becomes gritty.
Since these pears need to be picked somewhat green, they must be allowed to fully ripen off the tree before eating. You can do this by keeping the European pears at room temperature (60 to 70 degrees Fahrenheit) for 7 to 10 days. You can speed this up if you keep the pears in a sealed plastic bag since the fruit will give off ethylene gas, the "ripening hormone," inside the bag speeding the process up. If you want to speed up ripening even more, put your green pears in a paper bag with a ripe banana or apple - both of which give off even larger amounts of ethylene gas.
So how do you tell if a European pear has finally ripened? Dr. David Sugar of Oregon State University advises to "hold the pear in the palm of your hand and press the thumb of that hand on the pear just below where the stem meets the fruit. If the flesh yields evenly to gentle pressure, the pear is ready to eat."
You can store both types of pears after picking at 30 to 32 degrees Fahrenheit with a high relative humidity of around 90 percent in a perforated plastic bag for up to three months. Just be sure to remove the European pears from storage about a week before use in order to allow for ripening time.
Missourians enjoy both types of pears but we must remember to pick the European type green and the Asian type ripe. I think that Asian pears right off the tree are delicious and much juicier than either apples or European pears. Most of mine don't get the chance to last long in storage!