Yes, Valeriana officinalis.

Thank's to both of you! I am pretty sure the Lavatera at the link you recommended is right.

Cutting it will improve the shape, but if it's growing weak, droopy branches then you need to correct some cultural conditions or it will just grow more weak branches. The two most likely problems are lack of sun, and a water retentive soil. Lack of sun causes the branches to grow long and skinny in search of more light. A water retentive soil causes the roots to rot which deprives the plant of water, making it droop. Do cut the plant back, but make sure you give it lots of light and a porous soil so that future growth will be strong and healthy.

Think of these as two large in ground flower pots just like the ones on your porch. Your job is to make Flower Arrangements in them that are timed to bloom in the seasons you are out on the porch the most. Much easier to do in your compressed growing seasons. I would use herbaceous perennial plants instead of annuals unless you like the idea of changing things up every year. The number of flowering perennials to choose from is endless. You can seriously make an arrangement of almost any kind from simple to very complex. Remember there is more than just the flower, form and texture are big components of a good arrangement. Beds of herbaceous perennials won't fit neatly in a box. That is a good thing. There are enough smaller choices so it won't get out of scale. It will be billowy. I think billowy will help soften all that hard stone. The maintenance would entail keeping your arrangement fluffed in season, then cutting it all down at some point before it wakes back up in the spring. So think Flower Arrangement and go have a look at Wild Flower Farms catalog in Coldwater Ontario for some ideas. In this case I would get plants and not seed, but you can see what will grow just fine for you with no fuss. I feel certain Toronto is choke full of good local nurseries. Have you been to Garden Walk Buffalo or Niagara Falls (Canadian side, much nicer), both are flower bonanzas in season. Look them up for inspiration. Or if you like, this will take you on a three day private garden tour of Toronto gardens. Have fun!