I am keeping my ferns in the basement for the winter. Should I trim the ferns back while inside during the winter?
There is no need to trim your ferns back. Unlike some other houseplants, fern fronds do not branch or become bushier when pruned. Once a year, cut out any frond that is damaged, brown or really old and ugly. If you really wanted to, you could cut all the foliage off, keep the soil moist and with the right water and light, the fern should sprout again. It shouldn’t kill the fern, but I don’t see any advantage to doing this unless the plant is infested with pests. In that case, by eliminating the foliage, you might eliminate the pests and by starting again could better control any potential infestations.
It would be much healthier for your ferns if you repotted them. If you acquired your fern in the spring and had it outside all summer, it is probably rootbound – you could probably lift the entire fern easily out of the pot and see the roots growing around in circles. These roots become matted into a wall that actually prevents water from getting to the plant.
The easiest thing to do is remove the fern, take a large sharp knife and slice straight down through the soil, dividing the fern in half, then divide this half again. You now have four new ferns.
Before you repot them in a potting mix — splurge on the more expensive container gardening mixes that have good water retention and added organic matter — loosen the roots with your fingers. It’s like untangling knotty hair, and it won’t hurt the plant. You want to allow the roots to grow out into the new soil, not tangle up again by growing in circles. You can also remove any damaged fronds at this point. Ferns grow fast, so I suggest putting each piece in its own pot that is the same size as the pot the original plant came out of. Make sure the new pots have drainage holes. I use a layer of pieces of broken styrofoam meat trays to prevent the soil from washing out of the pot. The ferns will pout for a bit, but when you put them outside next year, before long you will have four bushy, green plants instead of one.
Remember also to ‘harden off’ the plants before you put them outside in the spring. If you just stick them outside, they will go into shock. Instead, gradually introduce them to outside conditions a few hours at a time.