Seeds have all the nutrients the newly germinated plants need until after they develop those first true leaves, there is no reason to "fertilize" them until then. Nitrogen deficiency is difficult to properly diagnose because the signs are similar to many other nutrients lacking, such as Potassium, Magnesium, Zinc, Iron, Sulfur, Boron, Copper, Manganese, and Molybdenum, depending on how the chlorosis, yellowing, of the leaves occurs. A purple coloring of the leaves is not a Nitrogen deficiency but may indicate a proplem with Phosphorus, low levels in the soil, plant unable to uptake the P because the soil is too cold, plant unable to uptake that P becasue the soil is too wet, a number of reasons for that to happen that may not have anything to do with the need to add a "fertilizer".

Have never planted much but I LOVE gardening so I figured I'd be over zealous this year and started some veggie seeds inside. I live in zone 5b (southern WI) and have some concerns I was hoping to get feedback on. I just planted my red cherry tomatoes on the 17th. The seed packet says they should sprout in 7-15 days... well it's 5 days later and they have all come up. They look skinny and the stems are long.. like almost 3 inches with the cotyledons at the top. This doesn't look like any of the pictures I've seen so I think I've done something wrong :( I used a seed starter mix soil blend and they are in containers with a plastic dome on top. At the plant store they told me that tomatoes like "warm" and to use a heating pad... so I did. I bought a "germinating heating pad." Since I've never done this before, I asked a ton of questions and was advised to not water them with tons of water but to spritz them with water- which I do once a day. I'm not sure if what is happening is okay, or if something is going terribly wrong. Am I over-watering them? Are they not getting enough light? (they're in a window) Is the heating pad causing this? Should I take the plastic domes off? Do I need to start over? HELP!!! I am determined and motivated to make this work :)

You can start them in pots anytime but look to keep moving to bigger pots as they will get quite large. Most start them around Christmas indoors. They can be transplanted outdoors when the weather starts to warm up in the spring with a wire cage made from "pig fence" and plastic wrap for protection against strong winds and cold nights.

Take a look at page 7 in this publication: Growing Your Own, A practical Guide to growing in Oregon: https://catalog.extension.oregonstate.edu/files/project/pdf/em9027.pdf And here's another link: http://www.gardeningbc.com/page/brianminter58.html