Last autumn I collected some seed balls from some beautiful trees growing in a park on a spur of the moment decision. The result as you can see in the above photo is pretty good. The seeds were soaked in water for 24 hours, drained and mixed with a little dry sand to separate them from each other to make sowing them a little easier .
They must have light to enable germination so they were sown in a seed tray on the compost surface. I made 5 short metal hoops to support transparent pallet wrapping film although a clear plastic bag would work equally well. After a day or so the water vapour begins to condense on the inside if the film indicating 100% humidity inside and the correct conditions for surface sown seed to germinate.
After approximately a week kept at room temperature signs of germination were evident. After another week or so covered by the film the edges were lifted slightly to increase air circulation and start to prepare the seedlings for life under more normal conditions