I’ve noticed many maple trees shed an early crop of seed, towards the end of May or mid-June. Are these seeds viable or do maples shed them to make way for the remaining seed clusters still on the tree? The ground beneath maples is soon covered at this time by these small green helicopters. During autumn, of course, maple seeds of a more substantial size are shed in equally short period of time. I’d like to know whether clearing away the small, first crop actually prevents seedlings developing.
Those “helicopters” produced by maples are a type of fruit known as a samara. As you likely can tell by watching them as they are shed from a tree, samaras are perfectly designed to be carried aloft in the wind to find a place to grow as far as possible from the shade of their parent. There is a seed at the end of each papery wing that will germinate if it lands in right conditions.
Maples produce samaras once per year, so the different “crops” you are noticing are likely from an early drop of immature seeds caused by heavy winds or rain from a Norway maple (Acer platanoides), and then the drop of mature seeds in the later summer or early autumn. Or it is also possible that you may have more than one species of maple in your vicinity. Silver maples (Acer saccharinum) drop greenish samaras in spring and early summer. If the helicopters are in a pair with an almost 180 degree spread and the seed pod at the end is flat – then these are likely immature Norway maples seeds that have been brought down early by wind or rain. These are unlikely to germinate as the seeds are not yet fully developed. If the samaras pairs are more droopy and closer together, and the seed pod is full, then these could be silver maples which most certainly will germinate if they find the right conditions.