Fern lifespan

I have a Polystichum setiferum (soft shield fern), which I planted 22 yrs ago. I have never divided it as I can't see an obvious way to do this. The above-ground base is a very solid, circular lump. Anyway, each spring I have trimmed off the old fronds as the new ones emerge, but, other than that, it has fended for itself. This yr, however, it is looking pretty sparse. It only threw up a few fronds. These are a healthy green, but somewhat floppy. Is it just old and near the end of its expected lifespan, or should I be helping it in some way and, if so, how?

 

It might just be done, if it's that age, but perhaps it's not coping well enough due to the site it's in? A bit like Irises - maybe needing the dead stuff removed to allow newer growth?
I find it best to divide ferns by using a saw if they're big - a pruning saw is usually enough for it, but it might need digging out and splitting with a standard wood saw.
They seed/spread everywhere here, so it's more often a case of pulling them out as they're a bit of a nuisance. They've been particularly vigorous this year - I've had to cut loads of them back completely, and one or two will need removed.

 

Thanks, @fairygirl. This one is not a self-seeder. It's an evergreen. I do remove the old fronds, but this spring there were hardly any new ones to unfurl in their place. It has always seemed happy enough in the site and, if anything, the conditions for it have improved over the yrs as other plants have grown up to block direct sun. It got lots of water this yr too, due to the weather. (It has never needed watering, even in very hot, dry summers.). This is what makes me think it might just be natural decline due to age.

I think I will leave it be and see what happens next spring.

 

I’ve got several of these ferns @ViewAhead but only about three years old. Because of my sandy soil I give them some BF&B in spring. I also find that my tree fern responds well to seaweed extract, applied to the trunk and crown. Both of these treatments may help your fern, plus some added organic matter around the base.

 

There's gravel round it, so adding organic matter isn't really an option, but I could try some seaweed feed.