American red raspberry is harvested once a year for spring-bearing varieties, and twice a year for ever-bearing varieties. According to Gary Gao of the Ohio State University Extension, "Compared with black raspberries, red raspberries tend to be more cold hardy, have larger berries and have more erect canes." Some varieties can be harvested mechanically, but most must be harvested by hand. Color, size, shape and sweetness are additional characteristics that determine readiness for harvest. Red raspberries have a short shelf life and are easy to damage during harvest, so take care to avoid damaging unripe fruit or flowering canes.
Check the calendar. According to the USDA Natural Resources Conservation Service, the fruit matures between July and September. Harvest spring-bearing varieties beginning in July. Harvest fall or ever-bearing varieties in mid or late October, as long as the nighttime temperature stays above freezing.
Check the color of your berries. Red raspberries are ready to harvest when they have a consistent red color. Harvest Algonquin, Canby, Chilcotin, Malahat and Skeena varieties when they are bright red. Harvest Comox, Haida, Meeker, Nootka, Qualicum, Sumner and Tulameen raspberries when they reach medium red. Harvest Willamette raspberries when they are dark red.
Use a centimeter ruler to check the size of your berries. According to the USDA Natural Resources Conservation Service, American red raspberries should be about 2cm long and about the same width, which is about the distance from the tip of your forefinger to your first knuckle. Leave smaller berries on the canes to continue growing, unless it is close to the end of the berry-picking season.
Check the overall shape of your berries. Ripe berries should have a rounded, conical to spheroid shape. The berries consist of multiple tiny berries in a cluster, making one large berry. Each of the tiny berries contains a seed, which is one way that red raspberries propagate.
Taste berries from various parts of each row. Red raspberries are sweet when they are ready for harvest. Unlike pears, which ripen after harvest, red raspberries do not continue to ripen.
Gently remove each berry from the cane without squeezing and place them in a fruit tray with a carrying handle.
Pass the harvester very slowly through the left third of the raspberry bush row. The wires of the harvester agitate the bushes, causing the berries to drop onto a conveyor.
Place fruit trays under the conveyor drop.
Pull any leaves or canes from the tray as the berries drop into it.
Place the tray in a fruit crate when it is full. Place a new fruit tray under the conveyor drop. Continue until all rows have been harvested on both sides.