Do you happen to know the variety name? If you have the seed packet, see what it says about the height.

There are strains of nasturtiums described as tall or climbing that can grow to 6 feet or more and do best if trained up a trellis. Others grow to 2 or 3 feet and would be effective trailing from a basket or over the edge of a raised bed. Some grow to only about a foot and could be used in a hanging basket but would probably only flop over the edge.

They make lovely hanging baskets and mine bloomed within six weeks of sowing outside. They breezed through our late cold snaps as long as I covered them when frost was forecast. Your summers are cooler than mine so you can probably keep them going a long time. This year was my first experience with them, and I love them. I planted a half dozen kinds and they all seem to be comparable in their performance so far. Unfortunately, they are starting to suffer from the heat in full sun already. I may try them again come fall and see how long they'll go into our cooler months.