After the last Spring frost transplants can be placed in the garden. You will have to find out your USDA planting zone and then you can see when the average last frost date in your area is.
The average frost date for zone 7 is approximately April 15th, with a variance of 15 days either way (~March 30 to April 30). Note that higher elevations may have an increased risk of frost late in the Spring despite the zone, and would fall on the later side of the average. There is no good way to guess the perfect date every year, but if you plant a garden and realize there may be frost, get your plastic and mulch ready.
I researched this question not only on the internet, but speaking to farmers in my area and they all agreed frost can occur until the last day in May. We are considered zone 5.
february of 2012
You can use your last frost date for your area, look up your planting zone(PA ranges from 5 in the north to 6 in the south I believe) and that will tell you when seedlings should be safe to plant outside. Then look at the back of your seed packet and it will tell you how long it takes them to grow. For example say your a zone 6 and last frost date is May 15 and your seeds take 6 weeks. You would count 6 weeks backward and start them April 1st so they could be planted out May 15.
In Zone 4, start seeds in a greenhouse 6-8 weeks before the last spring frost date, which is typically in early to mid-May. Be sure to adjust your planting schedule based on the specific needs of the plants you are growing. Consider using a seed starting tray with a heat mat to provide optimal conditions for germination.
Lemon Balm should be planted 6-8 weeks before the last spring frost in your planting zone. This could be as early as early March, but check your planting zone for the exact timing of planting it.
Anything buried in the frost affected zone may be shifted around at the frost settles and thaws. Not a good thing for conduits, pipes or foundations.
NFL Rush Zone Season of the Guardians - 2010 Frost and Ten 2-5 was released on: USA: 21 December 2012
Broccoli is started indoors in Late March/February and is transplanted into the garden in Late April or May depending on your last frost date. Your planting zone will dictate when you must start your seedlings and when you can transplant them into the garden.
Con Artist announced that Dead Zone will be released in it's beta form sometime in February of 2012. They did not give a specific date so it could be now or at the end of the month.
I believe it is th Zone of Transiton where the area is much poorer than the other zones.