Japanese maple seeds ripen in fall. Premature seed drop Is usually due to lack of fertilization but can also be stress related, similar to what occurs with any other type of tree. Production of seeds can be very erratic - very heavy in some years to almost none at all. Not every type of JM will produce seeds every year, some are shy to ever produce them and the age at which they will start producing seeds (reaching sexual maturity) can also vary widely by cultivar.

Since few grow these trees specifically for seed production, it's not a huge concern.

Thank you. I suppose this may have happened in previous years and I didn’t notice as my JM addiction hadn’t taken hold!

We have six old oak trees around our home and a few years ago, all of them decided not to produce acorns. I did notice that as clearing the leaves was so much easier!