hi Armayer!
a seeding in a 6l pot is a bit excessive and if you watered at planting it is going to take quite a while to use up all the water in the container, and actually because gravity settles all the water down to the bottom, a new plant just starting out can lose sight of the water that has settled deep down in a large container. Since our advice normally is to wait till the plant has used all of the water all the way to the bottom before watering again, it might take a week or longer for your new plant to use that lake you have provided for it. The problem is that since you have already broken the rules about using smaller containers for smaller plants, you now have to break another rule. Your tiny roots have not reached the bottom yet so there is no way they can use the water sitting there. You are going to have to water from the top again, so you can keep the roots alive long enough to be able to reach down to the bottom. Don't be excessive with this emergency watering, just give it enough to water the top roots and give them the ability to reach down to the bottom. Please note that the top being dry has nothing to do with this. What I am concerned about is the bottom of your new feeder roots not having water, several inches below the surface.
Once your plant has finally established in this large container by sending its feeder roots all the way to the bottom, attempt to restrain yourself from watering until the plant uses all the water that you gave it, all the way down to the bottom. Use the lift method to make sure this happens. It will drive you crazy, but there is going to be a point in here soon where you need to let her go for a week between waterings if you are going to do this correctly. For now, until you can be sure that the roots have gone deep (about a week old) water with small amounts every other day. Forget misting... that is not going to send the roots deep, it will train the plant that all the moisture is at the top... you need your plants to quickly settle into that large container and send those roots deep. If you can keep from watering and let the plant adjust into this container, and keep doing this through every water cycle until flower, you can recover from your mistake and end up with a root ball capable of producing superior pot. If you continue to make mistakes however and end up drowning these already potentially sickly roots by watering too often and fail to learn how to develop a root ball, your plant will be sickly, scraggly and will not produce anywhere near its capability.
Also, once established, so as to help your plants figure out what to do in this overly large container, water only around the outside edges, trying not to send water straight down the middle. This will make the outer edges the wettest spots in the container, enticing the roots to grow laterally to get that water. Having made the first mistake with the large container, now you have use extraordinary methods to develop a rootball.
Next time to avoid all this, start your plants in solo cups.... its much easier. Plan to up-pot 2 or 3 times during the grow so you can develop solid rootballs without resorting to extraordinary watering methods just to keep your plants alive.
