Fertilizer may, in fact be what is called for. It depends on why, specifically, these are declining.

Compost, compost, compost. Not the plants, but around them. In the wild, they have a continuous supply of leaf/needle litter falling, decomposing, falling again - keeping the soil moist and humusy

They do well for me under deciduous trees, where they get full sun in Spring until the trees leaf out, then shade in Summer. I fertilize them lightly every Spring. They get watered once every two weeks or so all Summer. The soil is always covered with bark, leaves, etc. They are slowly multiplying.

Thanks for the suggestions. They are growing in a deciduous woodland area but the soil is very thin and I do not water in summertime. Perhaps I should move them to a more fertile area with more soil. In the meantime, I will use some fert and perhaps some manure -- there are so many deer around here I can even use deer droppings! That should be wild enough...

I am not so sure about manure. I would try compost, about 4-6" spring and fall for a year or so and at least some water in the summer. If that doesn't work, you could try a very, very light application of a fertilizer for acid plants. I did that one year and mine got huge, but I don't know that that is a good thing.

My trilliums are huge and keep blooming and blooming - the native white, and a red flowered form.

They're growing in soil that over the years has been covered in many inches of goat manure, alfalfa hay, horse manure, chipper-shredder stuff, and are currently fertilized with urine diluted 1:10 in water, as described in the book Solviva. So I would not be afraid of fertilizer!

They're under fir and deciduous trees, and I never water in the summer. I think I'll start, though.

they've been blooming for 5 weeks now and no sign of stopping - they're gorgeous

Buzzy, you're trying to make me jealous! And I am...Mine are blooming in their little way, but wait till next year after I top them up with compost, etc...

they'll be great - lots of organic material seems to be the ticket, and the golden fertilizer, of course

I read about it in a wonderful book about greenhouse growing called Solviva - fantastic book. She calls the high powered fertilizer you're in charge - or urinecharge

next spring you'll be graced with trilliums, eh?