Is there currently a shop or place to get seeds in Omrazir?
No, there isn't any seed shop in Omrazir; all seeds have to be harvested from their respective plants. I don't actually have any way to just create a particular seed item! This could be a very cool PC-run shop for someone who wanted to collect seeds as they come into season and put them up for sale.
Are there commands besides 'garden' that should be used to maintain plants?
Garden is the only command that is currently needed to grow and maintain plants.
What factors into plants growing or not growing? (Skill level at planting? RNG? Weather factors?)
I think skill level plays into it somewhat, but I'm not sure what else lies beneath the hood for horticulture. I would have to dig around in the code to see.
If a fully grown plant has no noted things that can be harvested from it, is that potentially a discovery/skill roll issue or something that should be typoed?
Like Ighlaf said, a plant like this is generally one that is intended to have harvestable parts eventually, but they just haven't been added yet. Each harvestable part requires numerous lines of unique details to be written out for it, so implementing plants is a time-consuming process. And some plant parts that might produce special effects don't have those effects coded in yet.
