Is your stretch of hot weather due to be over soon? If so, I'd wait until your temps have cooled back into the normal range to reduce stress and plant in the garden.

I don't use that stuff. I make my own because it's much more cost effective. If you need to buy soil mix, find one that's not heavy on wood debris and consider adding sifted compost. Onions like nutrient rich soil to grow strong till transplanting. If I only need to germinate and plan on potting up (tomatoes, peppers) I use less compost or used soil. I never found a need for 'soil-less mix'. I think it's unnecessary. If you did use starter mix, you will need to feed heavily or pot up. As you said, that stuff doesn't have any nutrients. As far as pot size, with good soil you can cram quite a lot of onions into a small container as you can see in my photo, 1/4" apart is fine. Next time, consider starting in good soil and avoiding a step. Don't let this (or me) discourage you, I'm sure they will do great! Here's how I grow mine: This post was edited by madroneb on Sun, Feb 3, 13 at 1:40

Yeah but how do I know when it's time to pot them up? When they are 3 inches tall? 6 inches? The starter cups are 4 inches tall and 3 inches wide at the top that tapers down slightly to the bottom. There are holes on the sides and bottom to encourage more branching root growth.

I think that this issue bothers me more than most because of the area I am in. The majority of people here don't have enough dispensible income to buy plants and it is a difficult climate to grow a lot of different plants, so most people don't even care about plants. The nurseries around here have the same attitude and seem to not really care of the quality of their plants. It is very difficult to find plants that don't have problems. It's probably a 50/50 chance trying to find a plant that has a problem. In fact, I worked at a landscaping business here and I have heard my boss talk about plants that have been in the same 5 gallon container for their 4th year. The large nursery I worked for was in Oregon and it was much different there than here. People had the money, they had more knowledge, and there was also much more competition. Repotting was a problem at that nursery but the majority of our plants were excellent quality. Also because people were more educated about plants, any plants that weren't up to quality weren't bought. The plants that weren't up to quality just didn't sell. Like I said, I can't speak for every nursery but I know at this nursery I worked out, we had a large enough staff but there were problems w/ organization that even the owner would admit. I was able to visit many nurseries while I was in Oregon and I noticed that the most organized nurseries seemed to have the least amount of problems. I don't pull the plant out of the container either for the same reason you don't. What I have had luck with though is I have found a nursery where basically any plant I pick is going to be perfect. The only problem is, its two hours away but its worth it to me in the end. I agree with you about the label on plants also AND how some nurseries don't have the label or price on a SINGLE plant. You have to talk to someone at the front desk, then they have to look it up for every single plant!