All bartlett i know of can ripen on the tree and do taste very good that way but you will get heavier insect damage. Many are picked early rather than lose half a crop. Interesting thing people dont necessarily know who are growing pears is that bartlett has been used in many crosses. So harrow sweet as an example a child of bartlett can be ripened on the tree. Kieffer should not be ripened on the tree but is a bartlett cross. Mentioned it in this thread No Farmingdale in OH X F - #5 by clarkinks "We know Harrow sweet is a cross of Bartlett’ x Purdue 80-51. We can read info about that here Ashspublications.org . “Purdue 80-51 is a cross of Early Sweet X Old Home X Bartlett/Williams Selected in 1973; introduced 1982. “. Harrow delight was made by crossing Old Home x Early Sweet) x Bartlett and ripens on the tree. Bartlett seems to pass than on to many of the crosses made from it. The fact bartlett is used in breeding can make pollination tricky. Some pears grit increases when left longer on the tree and others like clapps favorite suffer from internal rot. AYRES pear (Anjou x Garber) cross can also ripen on the tree. Interesting thing when i bought ayers it was labeled red bartlett so when it ripened fine on the tree that should have confirmed it was so i thought but years later i realized i was the victim of mislabeling for about 20 years.