I have questions on general maintenance for the ferns in my garden. It is winter and the wood ferns (now about 4 feet in diameter) have fronds which are now partially brown. The deer ferns look similarly forlorn.
Should I prune all the old fronds off and let the new ones take over? How and when to do this without damaging emerging new growth?
Sources are divided on when and whether to prune wood ferns (Dryopteris). Some consider Dryopteris “self-cleaning,” meaning that the old fronds will eventually disintegrate on their own (Gardening with Woodland Plants by Karan Junker; Timber Press, 2007). If you are inclined to tidy up the look of your plants, they can be pruned of their old fronds after new growth begins in the spring (this can be risky: be careful not to cut the new fronds), or according to Pacific Northwest sources, in late February or early March before new growth starts. Rainyside Gardeners and Great Plant Picks, two Pacific Northwest resources, offer more information. Rainyside advocates pruning once there is new growth, and Great Plant Picks advocates pruning before new growth begins. The same is true for deer fern (Blechnum spicant, now renamed Struthiopteris spicant): “Old fronds should be cut back in late winter or early spring before new growth starts.”
This is a good general guide for pruning maintenance of ferns, written by Richie Steffen of the Hardy Fern Foundation. The first thing he points out is that cutting back ferns is purely an aesthetic choice; it is not necessary. If you do want to cut back, consider the type of fern: is it evergreen, winter-green, deciduous, or semi-evergreen? The answer to this question will determine the best practice.
My question has to do with the fall/winter foliage of bracken fern (Pteridium aquilinum). A friend trimmed the bracken to the ground. Will the bracken grow back next spring? This led to other questions. Does bracken lose only its leaves in the winter or does the entire plant die off? Does it spread through its roots or spores? Any information you have would be appreciated.
Bracken is deciduous, that is, the fronds die to the ground in winter and then regrow from the rhizomes in the spring. If your friend cut her bracken down to the ground late in the year there would be no problem. Even if it was earlier in the year, the bracken would probably survive. According to the fern books I read, people have tried mowing to remove their bracken with no success. The books also warn that bracken is very invasive and not recommended for small gardens. It spreads by underground rhizomes, maybe by spores as well, and can take over a large space in a very short time.
It might be a good idea to take a look at some pictures either in books or online (just enter the name in Google and select Images above the search box) to make sure this is what your friend has. Any deciduous fern (and even some evergreen ferns) can be cut to the ground in fall, but generally it is better to wait until the new fronds appear in spring to cut out the old fronds of evergreen ferns.
The USDA Plants Database provides further information.
Sources consulted:
The Plantfinder’s Guide to Garden Ferns (by Martin Rickard, 2000)
Ferns to Know and Grow (by F. Gordon Foster, 1984)
I have ostrich [deciduous] ferns [on the grounds I keep] and I was wondering if there is anything special that I should do for them for the winter. What I have been doing is putting ground up leaves in the bed, but beyond that, I’m not sure if there is anything else I should do!
Andrew MacHugh’s book, The Cultivation of Ferns (1992) says the following (from p. 47):
“In autumn, a mulch of well-rotted leafmould, peat or bark chippings should be given to ferns planted in open sites. […] In winter the fronds of deciduous ferns can be cut back to an inch above the crown. In areas subject to frost, the decayed fronds will provide some protection to the plant and should not be removed until the spring growth of new fronds shows signs of emerging.”