Balled and Burlapped plants.
'B&B' is the nursery lingo
These nursery standards are applied to trees, shrubs, containerized plants and other nursery stock so that nurseries, garden centers, landscapers and homeowners have a standardized guide for trading in green goods and plant materials. These official standards often provide planting specifications as well.
Inches are still used for plant standards in the United States, while the metric system is used elsewhere. For our examples we have used inches and feet as the basis of measurements. These charts are only provided to give the novice gardener some idea of what nursery standards look like, and are greatly simplified when compared to official guides.
Caliper of Tree Trunk / Average Tree Height
1 inch - 8 feet
1½ inches - 10 feet
2 inches - 12 feet
2½ inches - 13 feet
3 inches - 14 feet
Caliper is measured 6 inches above the ground for up to a 4 inch caliper size and measured 12 inches above the ground for larger sizes.
'Drum laced' root ball
Caliper of tree trunk / Minimum root ball diameter
1 inch - 15 inches
1½ inches - 19 inches
2 inches - 23 inches
2½ inches - 27 inches
3 inches - 31 inches
Hydraulic tree spades used for digging trees in the field.
The front spade is on a hinged frame so the spades can be moved in around a tree trunk, and then closed and centered around the desired tree. Hydraulic cylinders force the spades down through the earth and also cut the tree's roots. Various sized tree spades are available for the front of a skid steer loader for digging various root ball diameters. Root balls around 28 to 32 inches in diameter seem to be the most common sizes at tree nurseries.
DBH (Diameter Breast Height) - Diameter of the trunk of a tree is measured at 4½ feet above the ground.
Caliper - Diameter of the trunk measured 6 inches above the ground (up to and including 4 inch caliper size), and 12 inches above the ground for larger sizes.