Hi Ross

I really wouldn't waste money on trying to grow Jasmine in a window box, but looking at the date of your posting you may have already done it. Jasmine grows really huge and develops a big root ball. Those garden centre ones were probably forced and treated to bloom on a small plant but usually it needs to be tall before it blooms. You could try it and then transplant into the ground later. I find your better off with annuals for a window box if you put in long stay tenants like the Jasmine they use up all the nutrients and outgrow the box very quickly. Sorry to sound negative but thats my experience. If you like scent why not try some sweet williams or even pansys they wont get too big and give a lovely scent in the evening.

If you are after scent in a window box you could try petunias. Not all of them smell much so have a good sniff before you buy. And in the spring you could have hyacinths. A tip I use is to have three cheap plastic window boxes for each smart terracotta one. I have bought a size which just sits inside the good box without showing at all on the outside. Then to change the display I just take out the plastic one and replace with the next planting. I start with February gold daffodils underplanted with tulips, which come later. When they fade it's usually a bit chilly still for summer bedding so I put in some little box balls grown from cuttings. Later I change to the summer display. Back to box balls for the winter and start again with the daffs in the spring. The daffs can do about 5 years before they need replacing. It saves lugging heavy boxes through the house or trying to change compost and plants whilst hanging out of the windows. When not in use the window boxes are shoved down the side of the shed. The bulbs have died down so they don't mind. The box balls can cope with a bit of shade and the summer boxes will be empty.

Another advantage to to using plastic containers inside a terracotta one is that the compost will dry out less quickly.

My suggestion for deliciously scented flowers from summer to autumn is Nicotiana (but make sure you choose a strongly perfumed variety, because some are bred purely for looks). They are easy to raise from seed, and if the window-box is in a sheltered location they will be a short-lived perennial rather than an annual. Oh, and they only release their scent in the evening.