I am not certain which kind of plant it is exactly, it is either Elaeagnus à ebbingei, either some bread of Prunus Laurocerasus (looks more like the later, but I can't remember it flowering). In any case it is rather common hedge plant around here - and everywhere a-mess-looking kind of plant. It easily can grow up to 20 feet up if left unpruned and 10'wide... For where it is planted it is overkill and the logical thing would be just to dig it out for good, but since it is not ours and neighbors do not mind it...have to figure what to do with it . I was also planning to plant some bushes in front of it, but there still is the same issue with the maintenance, also to effectively cover it I practically need trees more than bushes, since not many bushes grow that high. Maintenance wise fence probably would be easiest solution, since then I just would have to cut whatever sticks out, also maybe if I go for the proper fence (or some vigorous and dense foliage climber) the shrubs just won't send shots our way due to the lack of sun. :/ Here is a link that might be useful:

This sounds like a job for a fence rather than plants, which will take up a fair amount of horizontal space with their width, as they grow.

Captturbo, The multiplex is actually extremely easy to groom to a formal type shape. On mature clumps they shoot over a short period of time so a once a year trim is all they need. Once a culm is topped it never grows again so all you have to trim yearly is the new culms that come up from the ground. If you go to this link it is a favorite restaurant of ours in Ocala, it is a Brazilian steak house. Zoom in and The bright green line in the picture right next to the A is a row of formal shaped multiplex that is perhaps 5 years in ground and was planted at 5 feet on center. If you mess with the street view feature you can actually get a good look at it. Here is a link that might be useful: formal bamboo

I'm also in Ontario. I agree with the above posters. You mention " tightly clipped" which sounds like you want it to have a neat and tidy appearance, but you also want flowers and you want 4 or 5 different species so that your hedge has colour most of the time. In terms of flowering shrubs up here, it would be tough to find 4 or 5 different 4 foot high flowering shrubs that would have a small diameter of 12-18 inches - I really can't think of any that I've seen in Ontario off-hand, let along 4 or 5 different types. Further, if you took different shrubs that are naturally larger than the 4 feet high by 12-18 inch diameter, and tried to clip them to keep within the 12-18 inch diameter, you'd most likely lose a lot of the flowering capability as you'd end up cutting off the ends with the flower buds. Lastly, if the shrubs are that close together overlapping each other, often one ends up shading the other and thus reducing the amount of flowers because they each limit sun access to each other. In terms of perennials instead, I think it would look really messy to have 5 different perennials tucked really close together to form a hedge. It certainly would not render a neat and tidy appearance. And it wouldn't really give a hedge appearance, it would look more like a garden that hasn't been maintained well. Each perennial has different characteristics - crowding a daylily beside a delphinium beside a daisy - not exactly neat and tidy. However, this is just my opinion, and you might like the look. More about perennials, it sounds like you really want flowers, but I'm not sure if you get enough sun to produce great flowering perennials. If it is really only 2 hours, not 3 in the morning, and 1, not 2 in the afternoon, you might find a lot of the flowering perennials struggle, especially if the morning sun is very early in the morning. Some like 6 or more hours of full-on sun (ie: 10 am to 4 pm) every day. They'll flower with less sun, but may not flower as much. If it were me, I would chose 4 or 5 of the tall and narrow grasses as the other posters suggested - I see them at the shopping malls or in mass plantings by the city , something like Karl Foerster feather grass, or some of the ones with the large plumes. I think they look gorgeous - neat and tidy for most of the year, elegant and they have a bit of a hedge-like look if grouped together. Thats what I would do - and then add colour to your property using annuals in pots.