Answer: The following info is taken from the American Horticultural Society's book, "Plant Propagation."
Honeylocust: Seeds need to be scarified before sowing to improve germination. Soak seeds in warm water for 48 hours. Mix with an equal volume of moist sand in a plastic bag and chill at 37 degrees F for 2-3 months. They should be sown in late autumn and will germinate when soil temps are 50-59.
Sweet gum: Sow outdoors (no special instructions). Or store in moist vermiculite for two months before sowing and keep in a bright spot with a night temperature of 59-68. Seeds should germinate within 6 weeks.
Elm: As soon as they ripen in mid to late fall, sow the winged seeds thinly in seed trays and overwinter outdoors. Or, store the seeds dry at 37 and sow in late winter.
Good luck with your germination!
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