Answer: Cyathea cooperi is the Australian Tree Fern. It's hardy to 20F but may suffer some damage to the fronds. If your garden generally remains about 20F in the winter, there is no need to move your plant indoors. If it gets colder than that, moving it inside is a good way to keep it alive. You can prune off the lower fronds without damaging the plant but be sure to leave some of the fronds for photosynthesis. Eventually your tree fern will grow too large for you to easily move it indoors and then out again so I hope your winter weather is mild enough for you to keep it out all year around.
Best wishes with your tree fern!
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