Natural seed regeneration can be obtained on moist sites with exacting site preparation. Seed should not be covered nor pressed into the soil of the seedbed. About 4 weeks after germination, beds should be thinned to 20 plants per square foot. Nursery beds are often stream sterilized or fumigated with methyl bromide to help control damping off. Harvesting In the Lower Mississippi Valley, seed ripening and dispersal takes place from mid-May through late August, while in the Northeastern US, it occurs slightly later.
Cottonwoods produce large seed crops nearly every year.
Yields and Economics Geyer studied two provenances of cottonwood germplasm, one from Missouri, the other from Nebraska. The stumps sprouted vigorously the following spring. Taphrina aurea, T. johansonii, Trametes hispida, Uncinula salicis, Valsa nivea, V. sordida, Venturia tremulae . Pezicula populi, Phellinus igniarius, Phyllosticta populina, Septotinia populiperda, Trametes sauveolens, Venturia macularis. Pontania bozemani, Trichiocampus viminalis.