Encouraging Scented Geraniums to Flower

I have several lovely scented geraniums from Richters (not surprising, because you folks are TOPS and I've always had fantastic plants and seeds from you folks!). The plants are very healthy and happy, but some of them don't seem to want to flower for me – can you suggest anything?
They are all getting lots of sun (east facing balcony), enough but not too much water, and, once every 2 weeks, miracle grow (I also have crushed eggshells on top of the soil – they seem to like this). I know some plants (e.g., orchids) are "encouraged" by putting them in the fridge for a while, but I don't want to attempt this with my geraniums unless I know it has a chance of working and won't harm them.
I'm also wondering if some of the varieties that tend to get a bit "viney" (e.g., "Prince of Orange') will still produce flowers once they are in this state. I've given plants from cuttings to several friends (plants are at least 1 year old) and these plants are doing very well in terms of stem and leaf growth, but don't seem to produce flowers.
I've had great luck with my geraniums and tried a few new varieties this year – the knotted geranium with yellow flowers is very beautiful, in part because it is so unusual. This plant is becoming one of my favourites – I just love it and will probably have to order more for gifts next year!!!

Some scented geraniums come from very sunny areas of the world (e.g. South Africa) and need more sun than an east facing balcony can supply and therefore never get enough light and possibly heat to bloom. Our display greenhouse gets very hot in summer and our scented geraniums do flower every summer. However you may find that if you do get them to bloom, you will be disappointed! The plants with the nicest scents have very sparse pale pink flowers and you may be just as happy to just enjoy their lovely scent.
Onr trick that can be used to overcome lack of light is to use high phosphate fertilizer at all times. (This is a trick that orchid growers use a lot to get high light plants to bloom at our latitudes.) This means that in the three numbers listed for the fertilizer, the middle number should be substantially larger than the other two. An example of such a fertilizer would be blossom booster fertilizers.
The summer of 2000 has been rather cool in our area and that could also be a reason why some of your geraniums refuse to bloom. In a greenhouse the problem is more that too much heat builds up for high elevation plants, but scented geraniums love it. You might try growing one or two of the non-bloomers on an interior windowsill- where you can even move it to follow the sun to see if this will get it to bloom.
Sometimes the difference between day and night temperature is the trigger for blooming. To increase the difference you could try moving the plants outside for the night and onto a hot sunny window for the day. Giving the plants a cool rest in the winter will also increase the chances of their flowering in late spring.