I am wondering about protecting my container plants, dahlias, bay trees, petunias, dianthus, etc, from frost over the winter. I have a large covered area that I could put them in but I am not sure if this would entirely protect them. Should I buy one of those plastic/temporary greenhouses and put them in this instead?
Dahlias can be left in the open ground in coastal areas but are at slightly greater risk of frost in a pot.
Bay trees are hardy, except in a very cold winter.
Petunias are tender and can be over-wintered in a frost-free greenhouse but are generally discarded each year.
Dianthus is mostly hardy and some kinds are annuals, or treated as annuals, and discarded.
Some might benefit from cover but must still have light. The key thing is to find out what individual plants need.
A greenhouse, made frost-free with a small heater, is necessary for some kinds of plants. A temporary greenhouse with no frost protection is of limited value.