Probably would benefit from several hours of morning sunlight or all day dappled shade/sun, as they are not shade plants, only shade tolerant. In fairly low limbed, evergreen shade, they will probably never bloom. Mulch may be retaining too much moisture in the soil. They require a location with good drainage and slightly on the dry side. Small rocks or gravel mixed into the soil, aids drainage in heavy soil.
If your tree roots are fairly large, they probably are not withdrawing much, if any, moisture from the soil. The small, hair-like roots near the drip line of the tree provide moisture and nutrients, the large roots provide stability to prevent the tree from toppling over from wind pressure.
Add some Dolomitic Lime(powdered) to the acidic soil. Hellebores perform best in Neutral(pH7.0) soil, but will usually perform well in soil with a pH above 6.5.
Was you plant blooming when purchased? If not, it may be too immature to set blooms.
Once you satisfy growing conditions, they will produce flowers every year and luxuriant, dark green foliage all summer and into fall. I grow hundreds of them and I have to move one occasionally to encourage it to bloom. I have also drowned one or two that were planted in or near water runoff areas.
Rb

Thanks for your very helpful answer. I had a good look at it today, and I see that in the center of the plant is some fresh young new leaf growth (finally), even though the older leaves/stalks are still a bit on the droopy side and, as mentioned... no flowers.

The trees are deciduous, so it gets a lot more light in winter/spring than in summer, so it's been getting just about the kind of light you describe since about November; once the elms leaf up, however, (they're juusssttt starting in our area) it will get much less than that.

It never lost its leaves over the winter, btw.

Thanks again!

I have acidic soil and hellebores would seem to just survive and not grow, so I tried spreading wood ashes around them several times a year (I heat with wood) and that really makes a difference for me.

Regarding drainage, you might consider lifting the plants and having a look at the roots.

I think it's probably the ph or drainage that's off, and more light might help ... but it could also be that the plant simply lacks vigor. I was moving some hellebores this week, plants that I grew from seed and are all the same age, and they vary from big floriferous clumps to little single-crown plants with a couple of leaves.

It's a bit of a myth about hellebores requiring neutral pH or not tolerant of acidic soil conditions, similar to that associated with clematis. Like most plants, their tolerance is to a relatively wide range of soil pH but extremes in either direction should be avoided. The PNW has naturally acidic soils, typically somewhere in 6.0-6.8 range, and hellebores thrive in this climate without extensive soil amendment. In fact, a good many large commercial breeding programs are undertaken here.

It would be my assessment that good drainage and adequate sunlight are the most critical factors to these plants flourishing and blooming well. And it is helpful to consider that these are quite drought tolerant once established as well - I'd support RB's theory about the mulch and soil moisture also.

FWIW, if we are discussing H. x hybridus, last season's foliage generally does look pretty droopy at this time of year and is one of several good reasons to cut it back to the base now. The new foliar growth emerging will be clean, very erect and a deep, vivid green. Finally, I'm not sure I'd be overly concerned about a plant that is less than a year in the ground not blooming - age/maturity and establishment may have a lot to do with that.

Gardengal...
In most of the Eastern US, we have Red clay, which can have pH as low as 3.5. For that reason, I always recommend addition of Dolomitic Lime when planting Hellebores, even in ammended soil. I was taught that by an experienced (65 yrs.)plantsman and Ecologist(PhD), who grows & hybridizes Helleborus, and it has worked well for me during the 25 years I have grown them.
I am very envious of the growing conditions (climate & soil) of gardeners in the PNW. I have tried many times to adapt some choice PNW Native plants (Asarum, Erythronium,Trillium, the list is long!)to my climate, but it seems that is not to be, for long term survival. :Rb

RB, I'd consider a pH of 3.5 very much in the extreme and would certainly amend my soil to accomodate hellebores in that situation! :-)) However, since amending to adjust soil pH is only a temporary measure at best and difficult to do to any significant degree, I'd wonder how well these plants would do long term in that type of environment anyway.

While I understand what you are saying, the point I was trying to make is that precisely specific soil pH is not necessary to their growth and health. The preferred range of pH for these plants is 6.0 to 7.5, which tends to be more towards the acidic side than the opposite.