Harvest pears after they pass tests regarding their color, sugar content and firmness. Hand-pick pears to avoid damaging the fruit. Pears flower in April and are ready for harvest by late summer. The fruit does not ripen after harvest, so it is counterproductive to pick them early.
Check the calendar. According to USA Pears, the fruit matures between late summer and early fall. Begin with red and green Bartlett pears in August. Harvest Anjou, Bosc, Comice, Seckel, Forelle and other red varieties in September.
Check the color of your pears to determine if they're ready for harvest. When they're ready to be picked, Bartlett pears are both yellow and red. Seckels are an even mix of maroon and olive green. Anjou pears are both red and green. Forelle pears are bright yellow with red freckles. Bosc pears are firm and brown, with a rough skin. Comice is mottled green and red. Concorde pears, a cross between Comice and Conference varieties, are yellow with a red blush. Starkimson pears are a brilliant red.
Test for firmness. According to USA Pears, "Firmness is determined by ... the force it takes for a rounded plunger to penetrate a peeled section of the pear." Use a Magness-Taylor pressure tester. To avoid error, use a 5/16-head and calibrate the tester before you begin. If pears are too firm, leave them on the tree to ripen longer.
Use a vegetable peeler or a pocket knife with a sharp, thin blade to peel away a section of skin before performing the test. Choose several pears of the same size from the top, bottom and sides of the tree, both near the trunk and out at the branch ends. Average their firmness levels. Test both the red and other-colored areas, but do not test any brown spots. Average the readings for multiple colors on the same pear. Use a watch with a sweep second hand when testing, and take two full seconds to insert the plunger into the fruit. Record the readings, detailing the fruit's position on the tree, color tested, number of seconds used to insert the plunger and which tree was used to provide the samples. Keep all measurements consistent each time the tree is tested.
Test the sugar content. Use the same pears you pressure tested. Cut a 1-inch square from each pear. Place in a blender with 1 tbsp. water. Liquefy each sample in a blender. Add 40 drops of the resulting liquid to a test tube. Label each test tube with a marker or sticker with all the location data from your pressure test chart. Add 10 drops of Benedict's solution to each test tube. Suspend the test tubes in a hot water bath. Heat the samples to 120 degrees F for five minutes. Note the color change. The solution will turn green, yellow or brick red, depending on sugar concentration. The sugar content should be around 15 percent, according to the USDA.