How to successfully grow japanese maples from seed

We are addicted to reproducing plants by seeds. In this guide we will show how to successfully grow japanese maples from seed.
The Japanese maple (Acer palmatum) is our preferred tree to start from scratch. The reason is that we use young plants as rootstock to graft several japanese maple varieties that we have: atropurpureum, dissectum, orange dream, little princess and so on.
We decided to write this specific guide of propagating Japanese maples from the seed, but the basic concepts are described in our general guide to seed germination.
Before sowing, we do the stratification of the seeds. There are many variations of the process, but we like to keep things simple. So we put the seeds in a paper envelope, submerge them in a glass of water, close in a plastic bag and put them in the refrigerator for 4 weeks (sometimes more).
If you leave them longer, you will see that they germinate even in the refrigerator.

Seeds germinate even in the fridge
Sometimes we do not use the paper bag, and the advantage of putting the seeds directly into the clear plastic bag is that we can see when germination occurs.
We used a simple seed tray. Just pay attention to the drainage holes. Often we have so many seeds that we need to improvise and use fruit transport boxes lined with a perforated plastic for drainage.
There are several recipes for germinating soil. Around here, we use half of peat and half of coarse sand. Peat helps to retain moisture while sand helps to drain. It’s the perfect combination for the seeds, never forget, you have to have the balance between drainage and moisture retention so that the seeds never dry out and never become flooded.
Then distribute the seeds as the image, with the wing up. If your seeds have no wing or if it is broken, don’t worry, the wing is only for the seeds to be carried by the wind.

Sow in container with the wing up
Finally, we gently water until the water leaves the drainage orifices. Be careful not to move the seeds.
You can also apply a fungicide to prevent “damping-off” after germination, but if you maintain good drainage and not excess water conditions, this is not essential.
We usually cover the trays with a glass or plastic and then with newspapers or something that prevents direct light. The “greenhouse effect” decreases evaporation and temperature differences between night and day and causes the seeds to germinate more quickly. The temperature must not exceed 24ºC.
To reinforce, be sure to protect the trays from the sun and the wind.