We can place them in Jiffy pots, or better yet, place them in moist 72-cell plant inserts using a medium like the following.
- 3 parts peat/1 part sand
- 90-95% peat/5-10% vermiculite
- 3 parts peat/1 part sand with an additional 5-10% vermiculite
We can cover the seeds with a tiny layer(1/8-inch) of vermiculite, or just cover with same mix. Alternatively, we can use a dibble or dowel to make a hole and bury seeds to their recommended depth.
After that, we put on a 4-inch dome, place them on a heat mat and leave them in darkness until the first ones sprout. This can be a few days. Then, we turn on the lights before the early starters have any chance to get leggy from lack of light.
As an option, we could turn a light on so that it is a few inches above the dome. Thus, some light for the early goers is better than nothing and will reduce the stalk from growing long and weak.
For the next 2-3 weeks, plain water is all they need while they are only 3-inches below the daylight led lights. We must make sure to monitor color because they will go slightly yellow if we are late on the food. At this point, 1/3 strength fertilizer is fine.
For most plants, 4 weeks or so in cells will be fine. For quick growers like Nasturtiums, we may find 2-3 weeks in a cell is max.
Once our plants are 4 weeks old or so, we can move them into 3.5-inch pots and continue to care for them under lights, move them into a cold frame or greenhouse, or get them adjusted to natural sunlight and transplant directly from the cell.