Answer: Seedlings usually do best if they have plenty of bright light, an evenly moist but not soggy soil, and good air circulation. If you haven't done so yet, you will need to thin your seedlings down to one per cell so they are not at all over crowded. Also make sure they are receiving enough light. (If you are using a fluorescent type light, keep it just a few inches above the seedlings.)
The parsley and the cool loving crops such as cabbage, cauliflower and broccoli can be moved out to a cold frame fairly early. The peppers and the basil however will not tolerate cold weather at all and should be set out later when the weather has begun to moderate and the soil has begun to warm. (This would be near your last average frost date.) The cold frame will provide some protection from wind, heavy rain and temperature swings and is used to acclimate the seedlings to being outdoors. Once they are acclimated they can be planted in the garden.
Once the seedlings are beginning to fill in their pots they can be moved to the cold frame (assuming the weather is cooperating). You will need to keep an eye on the cold frame to be sure to open it so it does not overheat durting the day and then close it at night and possibly even cover it with insulating materials if a severe freeze threatens.
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