With rows of trees stretching for more than 2,000 acres, individual pine trees blur into the next at UF’s Austin Cary Forest off Waldo Road in Alachua County. But on roughly 10 acres nestled in the middle, Aaron Smith keeps track of each tree, individual branches on the trees and the specific strobili on each branch.  

From January through March, Smith gets face-to-needle with the trees using a mechanical lift. He carefully selects a labeled bottle of yellow pollen, covers a branch with a special-made hood and fertilizes the strobili with the pollen.  

The male pollen and female strobili were matched long before Smith climbed the lift as part of the Cooperative Forest Genetics Research Program (CFGRP). The program has worked to enhance the quality and quantity of loblolly and slash pines through genetic breeding since 1953.  

The CFGRP now estimates that 99% of southern pine seedlings planted in Florida are products of the program. 

“If you look at it a naturally grown, what we would call an unimproved loblolly pine, versus a loblolly pine that’s coming out of our third cycle of breeding, the straightness of the improved varieties is remarkable,” said Smith, a tree improvement technician for the CFGRP. 

Compared with corn or carrots, the genetic breeding of pine trees has a short history, with only four or five generations compared to thousands. Smith said America’s virgin forests were nearly gone entering the 1950s, prompting changes to the forestry industry.  

Smith said foresters began planting pine trees just like farmers grow corn. The change in practice allowed genetic breeding to enter the industry.  

The CFGRP started soon after. It’s a collective of members that includes UF, three timber companies, two seedling nurseries and two state agencies—the Florida Forest Service and Georgia Forestry Commission. 

UF serves as the coordinating member, but Smith said each partner has a role in the breeding process—and each benefit from the results.  

Smith said the project tries to enhance different characteristics with each generation. One might focus on straightness, another on wood density followed by an emphasis on disease resistance.  

For foresters who sell pine trees, diseases like fusiform rust can damage profits by rendering sections of the tree unusable. Qualities like straightness also benefit end users who pick up 2x4s to build a front porch.  

The program also looks at how quickly the plant grows from a seed—a benefit for nurseries.  

“Because of the unique nature of breeding pine trees—it’s slower than agricultural crops like corn and it’s just the scale that it has to take place on—that’s the way the co-op benefits,” Smith said.    

Agricultural crops can have a new generation each year or even more frequently. Plus, these crops can fit more plants within an acre than pine trees.  

Smith’s work on the lift helps accelerate the process.  

He takes pine seedlings that look promising and grafts them into the upper branches of trees at the Austin Cary Forest. The grafting process tricks the branch into thinking its ready for reproduction, causing strobili to form.  

Smith then pollinates the strobili and waits for 18 months. Then, the new cones are ready to harvest, plant and wait until it’s old enough to check the pine specimen for select characteristics.  

Harvesting the 18-month-old specimen happens in September, and the pollinating work gets busy from January through March.  

Smith said his life revolves around the strobili during those months, carefully waiting until the optimal time to fertilize. With warm, dry weather, the strobili could be ready earlier—even by Christmas. Cold and wet weather pushes back the timeframe.  

The strobili open like a blossoming flower, staying at peak fertilization for only a few days. That’s when Smith is on the lift and driving up and down the rows.  

The fertilizing process, though artificial, tries to mimic the natural process.  

In nature, Pollen floats through the air until it lands on strobili, and Smith uses an air cyclone to puff the pollen into the bag that surrounds the branch and keeps wild pollens excluded. 

The bag, called a pollen-exclusion bag, is specially made to allow air and water to pass through while excluding pollen. Smith keeps the bags on the branches until the strobili hardens and isn’t receptive to more pollen. 

Pollen forms on pollen cones, found in the lower branches on pine trees while strobili grow in the upper branches. The collected pollen is put in paper bags in a room full of fans to dry. A large sieve then separates the pollen from other organic tree material. After sitting in a freezer for months, the pollen can then be used in the next batch of grafting and breeding. 

Smith said the CFGRP has the exact pedigree of each tree, from parents to grandparents and great-grandparents. 

“That’s basically the crux of our breeding efforts,” Smith said. “We have cones on a known branch and then we take pollen from a known tree, and we apply the pollen to the cones. But we do so within a pollen-exclusion bag, so that we’re not getting any contamination of wild unknown pollen.” 

Smith said the CFGRP wants to encourage quality along with quantity to help end users. He said no one wants to look down the length of a 2×4 and see it veering off to the side. The program also wants to ensure wood density even with faster harvesting compared with the virgin forests of America’s past.  

It’s all taken into the mix as the CFGRP plans how to breed the next generation of pine trees that span the southeast. And it all comes down to tiny specks of pollen that Smith aims at specific strobili on specific branches of specific trees in UF’s Austin Cary Forest.