They should be fine, if you are worried go throw a sheet or light blanket over them-literally. It helps any foliage that may be harmed. 55 is a quite good temp, try to 'harden off' any plants you bring from in to outside however, its Pretty much letting them sit in the shade outside for some days, then some sun, then more sun, careful of the wind (wind burn) yaghta yaghta for 2 weeks or so and they are 'hardened' . And ready for the outdoors.