It kinda depends on how fast you want them to grow. 75 is optimum. Cooler temps will just slow down growth as will low light levels. I like to wait until they are starting on their second set of true leaves but then I don't use tiny seed starting cells - I use 4 inch deep trays so I can let things get bigger without transplanting them up as they grow.

You don't want them to get too big too fast. You want them at a certain level of development when the outside weather is the best for that type of plant. Timing is everything. If you can treat them in groups and not push all of them to size up you can cover all bases with some ahead of schedule and others behind - that way if we have a freak winter storm the first week of May you have back up plants.

Thank you John. Informative, as always.

I use a variety of containers depending on what I am planting. I do have a few in the 1x1x1.5 inch cell trays but as of today, most of them are in the 48 cell flats that are 3 inches deep. The soil depth is probably only two and a half inches deep though because I wanted to make room to put glass over them. For things, specifically annuals, that are going to spend the growing season in a container, I generally just plant them in the container they are going to live that growing season and slap a sheet of glass over it.

I'm not concerned so much with how big they are as much as I am with the quality, so yeah.. good plan. Thanks again for your input.