Question
when is the best time collect the seed of acer palmatum?

Answer
Collect JM seed (samara) just as the wings begin to turn brown in the fall.  Around August or September would be the best time. When you first start to see brown forming on the wings would be ideal. You can wait until the entire samara is brown and have success.  You don't want to collect much earlier than that because you run risk of the seeds not having been completely formed.
Acer palmatum seed is notorious for germinating sporadically. Germination of Japanese maple seeds (Acer palmatum) is not difficult, but it can be a bit tricky if your wife or husband doesn't let you take over part of the refrigerator!
First of all we soak the seeds in lukewarm (not hot!) water for 48 hours. This softens the seed coat a little. Next we mix the seed with a little damp (not too wet) sphagnum moss or peat and put it in a plastic zipper bag. Leave the seeds in this humid atmosphere for 4-6 weeks at room temperature.

Now comes the tough part - leave the zipper bag in the refrigerator for 60 to 90 days. This is to mimic the natural action of seeds going through a winter season. Technically it is called 'stratification'.

After the 90 days sow in trays or pots filled with a good seed compost. If you have a seed propagator use it or find a warm place to maintain a steady temperature of 65-70F (18-20C)

Cover the seeds to their own depth: ?Inch (6 mm) with seed compost.


Transplant seedlings when large enough to handle into 2-3 inch pots.