An open pollinated (OP) tree is a cross between a known, superior mother tree and a random father tree from an orchard of known superior genetics. At ArborGen, open pollination takes place in a seed orchard, which over a period of 50 years, has been selected to contain only the best performing trees. An OP seedling from ArborGen starts with the most productive and high quality parents.

1.5-Generation
The 1.5-generation seedlings were developed by putting all the best first-generation orchard parents into one orchard. By breeding the best parents, you are assured of getting the very best seedlings from the original wild selections.

Second-Generation
Geneticists researched and identified the very best crosses and then selected the very best individual trees within those crosses. As with their first-generation parents, these young second-generation trees excelled in growth and stem form and were disease resistant. Most were selected in the 1970s and 1980s and then promptly grafted into second-generation seed orchards. Generally, these trees are faster growing and more disease resistant than their first-generation parents.

Second-Generation Select
The best families from the second-generation seed orchards are available as "second-generation select" seedlings. They have a higher growth rate than base level second-generation seedlings.

2.5-Generation
After researchers tested and ranked all second-generation trees, the superior ones were grafted into "2.5-generation" orchards. Using only the exceptional parents means that these families offer enhanced growth over second-generation or second-generation select material.

Third-Generation
After identifying the most valuable second-generation families, researchers selected the outstanding trees within these families in the 1990s. These were large, straight and disease-free. On average, these grow faster than their second-generation parents.

Third-Cycle
Each generation of improved trees is better than the generation before. Still, there are excellent parents from all generations, and there is no reason that seed orchards must be composed of a single-generation population. The third-cycle seed orchards contain the very best of the first and second generations and have the highest rated third-generation material, too. In genetic value, third-cycle families are similar to or better than 2.5-generation families.

Elite
Even among the best trees, you can still identify and separate out the very best families. Regardless of generation, there are a few that simply outperform others. These are sold as "Elite" families.