I can't help you with Maria, but I thought I'd point out that a number of posters have claimed that RMV did not noticeably affect their roses other than the zigzagged lines appearing on the leaves at certain times of the year (dependent on weather conditions? I don't know.) My Earth Song exhibited those marked leaves for a few weeks last year, but hasn't since. None at all this year so far. As far as I can tell, my Earth Song is a heavy bloomer and is growing very healthily. So I don't worry about it one way or another. It might be, in your case, that even a non-virused Maria is not a good bloomer.

Kate

That could be true.
Last year, she had those zigzag lines on some leaves and it disappeared when warm weather came.
This year she developed those zigzag lines early and they are still showing on the older "new" growth. Only the growth that came later on in early summer has looked healthy.
She is planted by herself with no roses right around her, except for a couple roses about 10 ft away, so I don't really worry too much about it spreading to them.
If she looks even worse next year, I'll know it may be time to shovel prune then. I don't mind some leaves with lines, but progressive discoloration would be a problem for me.
But, whatever, she is a lovely rose anyways when she does give me some blooms.

I also have a virused 'Maria Stern'. (I hope there's a source somewhere that offers an unvirused selection of this fine, very elegant rose -- perhaps someone here knows of one.) I'd advise you to give MS a full three seasons in your garden before you pass judgement on her. Until then, pay more attention to the bush itself than to the number of blooms it produces. MS can be a sturdy, vigorous plant even when virused, but it takes a while to settle in. My 5/6 yr old plant doesn't bloom heavily, but it reliably repeats. In my garden, I think it's at its best in autumn when the color takes on a special depth and vibrance.

This rose was recommended to me by a friend who gardens in New England, so I wasn't expecting much when I planted it in my much warmer zone. It has quite an interesting pedigree and seems to perform well under a wide a variety of conditions.

There is no general rule for the number of blooms any one particular hybrid tea will produce. It depend on the variety, maturity in your garden and the care you provide in the form of water, pruning, and fertilizer. A lot depends on your local conditions such as soil, weather, growing zone, etc.
Because you're in zone 5b, winter plays a big role as winter damage can affect the following year's bloom.
jaxondel's comments were right on.

Trying to asnwer your general question: for established HTs that have to be pruned way down after winter, I might expect 10-15 roses in the spring flush and 25-40 in the third flush, but my old Elina gives 40 in the first flush and probably 200 per year. In climates where hard pruning is not necessary, naturally the bigger plants bear more roses.

Wow Michael! I wish I had that many blooms! I'm lucky to see a couple dozen a year!

I think your general HT question defies succinct response simply because it's futile to attempt to make meaningful generalizations about a whole class of roses. Some HTs are naturally prolific of bloom, some are naturally stingy, most fall somewhere in between. Factors of culture, climate, disease (RMV, for instance), age of the plant, etc serve only to further accentuate/complicate inherent differences among varieties. To expect even a healthy 'Maria Stern' to produce on par with an exceptionally vigorous performer like 'Elina' is unfair to 'Maria Stern', and is setting the grower up for disappointment.

I pay no attention to whether a rose is virused or not unless it doesn't grow. In my garden Rose Mosiac virus hasn't been a problem. Virus symptoms usually disappear unless stressful weather conditions bring in on.

I'm wondering if any of you have purchased 'Maria Stern' from Pickering. If so, how long have you had it, and does it appear to be RMV-free?

I know I didn't. I purchased her at Dutch Gardens before I knew any better to look around at that. I did email Roses Unlimited to see if their stock of Maria Stern was virus indexed, but they said they can't quarantee anything basically. So, I too wonder about Pickering's Maria Stern. Could be that there ARE no virus-free offering of MS.

There are techniques for getting a lot of blooms out of one plant, such as pegging the cane, so that it produces a lot of laterals. But, someone growing that same rose for exhibition may be happy with just a few blooms, as Queen of the show is typically awarded to a single bloom on a long straight stem. The extra blooms are removed in an effort to make the few blooms you do get as big and as perfect as possible. Harder pruning generally results in longer stems, while light pruning often results in more blooms (just removing the flowers and leaving all the leaves). Often, light pruning will result in "self pegging," the canes will flop over all by themselves, producing laterals and more blooms.

I've found that recent plants from Pickering are free of RMV--I just got a new Electric Blanket/Salmon Vigorosa that shows no sign of RMV--though it is quite visible in the three plants in our yard known to have RMV, including a J&P Electric Blanket purchased years ago before they started virus indexing their plant material.