There are 2 ways to get bare root trees:
1. Trees and shrubs that are harvested when dormant in the fall; over-Winter in a cool, high humidity environment; and are sold without soil around the roots in the early Spring. Until the 1940's almost all trees were sold this way. Then big retailers decided they needed to be able to offer trees longer into the season, so they started putting these plants/trees in pots. This wasn't better for the trees or the consumer, it was only better for the retailers.
2. Fully leafed out and growing trees harvested from our Missouri Gravel Bed (see our Missouri Gravel tab). These plants/trees generally have a much greater root mass and fibrous roots than container plants/trees. Their roots are dipped into a product called Soil-Moist with mycorrhizae (a symbiotic fungi), to keep the roots moist and help reduce transplant stress. The trees are light and easy to handle for transport, with all of the benefits of traditional bare root.
Dormant bare root trees and plants are harvested after they "go to sleep for the winter" and "wake up" in the soil they're going to grow in. Missouri Gravel Bed trees, that are transplanted fully leafed out and are sometimes even growing fruit, have a much larger root mass which allows the plants to take in more water & nutrition upon transplanting. Both methods greatly decreases transplant shock.
Plants can grow roots much faster than they produce green growth up above. Potted plants often become root bound, where the roots start spiraling around the bottom of the pot (the longer they're in the pot, the worse this gets.) When these trees are transplanted, the roots often continue to grow in a circular pattern, where the roots don't grow outside the initial planting hole. This is called "flower potting." Even if the tree doesn't die, the root system is often greatly compromised, resulting in poor growth and loss of fruit production. This process can take several years and is often what we find when we're called to look at someone's trees that have failed to produce fruit as expected.
With planting, it's CRITICAL to get the proper depth. Trees and shrubs should never be planted with the top roots deeper than 2" below the soil. Any deeper and the roots can grow around the trunk and girdle/strangle the tree as it grows. This is the #1 biggest cause for tree failure with potted and balled & burlapped trees where the soil with the plant hides these top roots. With bare root trees, the primary roots are visible so you can ensure precise planting depth. You can also limit the amount of disturbed soil beneath the plant so it doesn't settle and become more than 2" deep.
Another big problem with potted plants is the planting media in the pot is meant to shed water so plants aren't over-watered in the nursery, whereas natural soil retains water at the soil/root interface. It takes time for the roots to grow from the potting medium into the soil, where the water retention is better.
Trees harvested with surrounding soil are very heavy. This means that root ball has to be kept small in order to transport the trees. With bare root, this isn't a problem so more roots can be, and are, taken when the tree is harvested. Often when trees are replanted from the growing fields into the pot, many of the roots must be removed to fit in the pot.
If the roots on a bare root tree are damaged or if they were growing oddly for some reason, this can be corrected before planting. This helps keep the tree healthier and helps it grow faster.