Nurseries that sell landscape sized B&B and containerized trees typically buy bare root ‘liners’ from other nurseries specializing in liner production. For most northern states, the most common source of liners is the Pacific Northwest where they can be produced rapidly and inexpensively in the field.

View larger

In warm climates, such as the southern US, tree liners are often produced in containers. Typically, the stems are not cut back in this production method, as they are in field-produced liners.

View larger

Soil cultivation in the nursery fields can affect root depth in two ways. Frequent cultivation will usually keep roots from developing in the first couple of inches of soil. Unlike the forest where the soil is protected from drying by leaf litter ‘mulch’, the frequent drying of this bare soil between rainfall events or irrigation cycles also discourages root development at the surface.

View larger

Cultivation practices can also mound soil around the base of trees. If not removed before harvesting, it will add soil to the root ball above the structural roots.

View larger

Planting liners too deep has been a major reason for deep structural roots, though the situation is improving rapidly. Some growers would purposely plant the liners too deep in order to reduce the need for staking, to control sprouts from rootstock, to protect the bud union, and hide the crook in the stem from the grafting and cutback process.

Growers may have assumed that new adventitious roots would form on the root shank above the adventitious root flare. Only a few species will do this. Usually those adapted to floodplains where the soil level is periodically raised by added silt. They may have simply been unaware that this could be a problem since the trees would grow well in their high quality nursery soils.

View larger

Field-grown bare root liners are often planted in containers and sold after a season in the container. If not planted correctly, the structural roots can easily be too deep. (photo by: D. Fare)

View larger

The graft union should be visible, just as when the liner was growing in the field.

View larger

Containerized trees with deep roots can develop large amounts of fine roots above the structural roots. This may lead to some difficult decisions when planting. (photo by: D. Fare)

View larger