I am always anxious to get my plants out as soon as possible and sometimes it is imperative given the contraints of the seasons. It is important to not get complacent after you have planted, particularly in the Spring. Most of us are aware of frost free dates and how they affect when you should plant. But as all of us should be well aware of, mother nature can be fickle.
The national weather service for my area publishes April 30th as the frost free date (10%). Note the 10%, that means that 10% of the time it will frost after April 30th. This is important because while 9 years out of 10 it will not frost after April 30th, sometimes it will. Technically, no one can officially publish a sure fire, never will happen frost free date because, lets face it, anything can happen. 10% is usually close enough. Therefore, I have a few suggestions during this critical period.
Keep an eye on the weather min and max predictions each day. By keeping an eye on the weather each day you may be able to save your plants from an early death. If the temperature is predicted to go below 40 degrees (F) then consider protecting your tender starts during the night.
Tender plants include tomatoes, peppers, eggplant, beans, corn, potatoes and others. If these plants are just a seed and have yet to germinate then I would not worry about a chilly night since the ground temp probably won’t freeze after your frost free date. But if the plant has green out then you can protect the plant with a hotcap (click to see picture). If the plant is a bit more sturdy then you can throw some thin plastic over the top, making sure to drape over the plant and secure so that the wind/air won’t blow right through or blow it away. Make sure to take it off in the morning before the sun gets too hot or you will burn your plants.
There are several other measure you can take, you just need to keep the temperature above freezing around the plant so that it won’t die. You do not need to do this for your hardy plants such as lettuce, broccoli, carrots etc.
I would keep a keen eye on your plants until about two weeks after your frost free date (10%), after that you should be good. For more information about frost free dates, check out this video on the subject.