Question growing maple seeds.

[Maloghurst]

Hello, I have germinated a bunch of trident and Japanese maple seeds. I built a box, filled with medium, spread all the seeds out and covered with about 1/4” of medium.
I have a piece of glass that could completely cover the box and increase temp and humidity or I should I put screen over the box and leave to the elements.
I live in Seattle and expect nighttime temps to stay above 30.
Thanks for the advice, mike

 

[Shibui]

I would just use screen to allow the elements to act. Seeds will grow naturally when they are ready. Forcing early germination can lead to problems if there's unexpected cold weather later. Glass cover also hold humidity which can promote fungal infection. There's also the possibility of overheating if you are not watching closely.
There's plenty of time for them to grow over summer without early germination.
How deep is the soil? Looks pretty shallow. There are some that believe shallow soil is good to promote lateral roots. I'm not a fan as it can also cause other problems and much better lateral roots can easily be promoted by root pruning.

 

[Maloghurst]

Soil is about 4-5 inches deep

 

[Forsoothe!]

Just protect from critters. Birds know what maple syrup tastes like, and if you live close to a House of Pancakes...

 

[River's Edge]

Hello, I have germinated a bunch of trident and Japanese maple seeds. I built a box, filled with medium, spread all the seeds out and covered with about 1/4” of medium.
I have a piece of glass that could completely cover the box and increase temp and humidity or I should I put screen over the box and leave to the elements.
I live in Seattle and expect nighttime temps to stay above 30.
Thanks for the advice, mike
View attachment 292116

I would build up the sides ( higher and add screen to protect seedling! Glass will create too much swing in temperature, trap too much humidity and promote fungal issues with restricted air movement. Just ensure you can raise the screen as seedling grow. Perhaps pic pipe hoops instead of boards to raise the height.