With thirteen little seedlings in a on the way, it was time to set up their homes for the next 2-3 years. I'm going to keep the seedlings in plastic 5/4 gallon pots of soil/sand mixture, fertilizing them bi-weekly with a soluble 24-8-16 mixture from Welker's Nursery, designed especially for potted giant sequoias.
For the soil mixture, I combined all that I had read online with some small changes to cut costs. It's very important for the soil to be well-drained, so I filled the bottom 1 1/2 inches of the pot with drainage rock. The soil is a mixture of roughly half tree & shrub planting mix and half cheap potting soil, along with about 1/8 sand mixed in for drainage (I'm aware that doesn't add up to 1, but am too lazy to do anything about it).