Hello, Andrea, welcome to DPC! A nice idea for your first entry.
The first thing that strikes me about this picture is that it doesn't meet the challenge description. A duotone image is really only suppossed to have two color tones. I understand that you were trying to emphasize the dead rose vs. the live one, but your photo is really a color photograph, which is probably the major reason voters marked it down.
Your choice of lighting creates a dramatic feel to the photo, and the shadow patterns on the wall and leaves adds a level of interest to it as well. Though it seems a bit harsh on the live rose, and the whiteness is kind of distracting, even a little blinding.
As far as composition goes, the image feels rather unbalanced, mostly due to the position of the leaves. It gives your photo an asymmetric look, which isn't always a bad thing but in this case detracts from the composition. Arranging the heads of the flowers the way you did works well, but they fill so much of the image that it feels top-heavy. Maybe a wider crop, letting there be more negative space to open it up more.
Don't let the DNMC and low votes discourage you...it takes a couple of challenges to get the feel of how things work here. Keep trying to get your ideas across to the voters, but above all, take pictures that you enjoy, have fun, and learn from what you're doing here :)
It is two tones, but I am not scoring high on color photos. I know this one would not have come out very well applying duotone, so you might want to really take a lot of photos to see what works best in black and white.
Unfortunately there are many flower photos in this competition, the contract of the two flowers is really nice, however this isn't really a duotone and I imagine it'll get hit quite hard to this. Lighting is good, however a little harsh in places
Creative duotone. The highlights are a bit of an issue for me. I like the lighting on the new rose however it produced a distracting hot strip in the background. Maybe diffuse the natural light just a bit so that the background color in that area isn't lost.
Beautiful color with nice textures and light play. Alas, you will undoubtedly get butchered by the DNMC crowd. Don't think it means your photo isn't beautiful - it is.