evidence: I like sweetgum trees, but most people run from them, versus wanting to plant them. The spiny fruit does contain seeds, in fact, quite a few. Each sweetgum ball has about 40 to 60 capsules, with each containing one or two seeds. Fertile seeds are black with wings on either side; infertile seeds are yellow and wingless. Harvest the sweetgum balls when they are fully brown, but before they dry out. Once they dry, they open and scatter the seeds. Harvest the sweetgum balls and let them dry out on sheet of paper. Then when the seeds start to fall out, collect them and put the fertile seeds inside a plastic bag filled with moist sterile potting soil. Put that in your refrigerator for three months and then plant the seeds in a pot outside. This cool, moist storage period in the refrigerator is known as stratification and is needed to break the seed dormancy. As an aside, researchers have discovered that the unripe fruit of the sweetgum tree contains a key ingredient used in Tamiflu called Shikimic acid.