I know it's early, only mid February, but it's time to get started thinking about and planting your seedlings for this years garden. Some seeds take longer to germinate or are slower growing than others. You want to keep all your seedlings about the same size (as much as possible) on one tray, so i can keep them all 2" under the lights at all times. This is how close you want your seedlings to be. So, I start some seeds before other seeds to keep their growth rate even. In 2014 i didn't soak my parsley seeds. If you don't don't some seeds before planting they can take 3x longer to germinate. Parsley will take 3 weeks without soaking, but about 7 days if you soak the seeds overnight before planting. Celery, onions, leeks also benefit from soaking overnight before planting.
Even if you've planted seedlings for years, it's always good to keep a seedling log, I learn new things and write them down every year. It helps me do things better each year, and new stuff always comes up. Logs will help you track things, and you can refer to them the next year to refine how you're growing your seedlings. On every seed pack, or in seed catalogs, they will tell you how long a seed takes to germinate. It's always a range, i.e. 7 - 14 days. The reason for that range is depending on how warm the area is, how you planted the seedlings, the light source you're using, all of that will impact how fast or slow a seed takes to germinate. When you keep a seedling log, you are finding out how long the seeds take to germinate in your growing conditions. You can also track how fast different seeds grow, so that you can plan on when to start each different variety of seed, and give them all the best growing conditions they need.
Always pay attention to the information on seed packs and/or seed catalogs. They will give you great information on when to start your seedlings, how long they take to germinate and when to plant them outdoors. Knowing your final frost date is important. Here in New Haven CT our final frost date is May 15th. So, if a seed pack tells me to start my seeds indoors, 6 weeks before the final frost, that means i'll plant the seeds around April 1st. This information is important; while i start parsley very early, hot peppers, celery, eggplants a bit further on.. i won't start my regular tomatoes till early April. Tomato plants grow really fast and if you start them too soon they'll be leggy and the plants will be weak (though it's easy to deal with leggy tomato seedlings, more on that later).
For now, start planning your seedling plantings, keep a log.. and i'll post some more info on lights and good growing conditions soon.