Erysimum. Probably Bowles Mauve.

Isn't Dames Rocket a biennial? It doesn't bloom until the second year and then it dies. My friend tries to sow some every year so she has some blooming each year. I can't guarantee the bloom!

Plant asked about is not a Hesperis.

Thanks for the responses. I believe it is erysimum but it dames rocket looks very similar. It is planted in my garden now and looks beautiful.

I promise you it is 100% not Hesperis matronalis. Although both plants are purple flowered Brassicaceae that's where the resemblance ends. Leaves and habit are quite different. Unfortunately there are pictures on the web where Erysimum, Hesperis and Lunaria are all confused and mislabelled. In mildish climates like mine Erysimum 'Bowles Mauve' can persist for several years and often flowers for months on end including winter.

I am somewhat surprised anyone intentionally plants dame's rocket (which the subject plant is not), as it is considered an invasive species or noxious weed across much of the country. And once planted, you will generally have it forever unless it is intentionally weeded out, as it seeds prolifically. Which is a primary reason why it is considered invasive.........that and the fact it will grow under just about any conditions.

I think Pinsk was saying the Erysimum is now planted in her garden.

I think GG was referring to xiangirl's friend, not the OP. 'My friend tries to sow some every year so she has some blooming each year.'

I have intentionally planted Hesperis matronalis on my allotment. It died out after one year and I've never seen it since. Seems to be yet another plant which is a problem in the US but not in the UK.

LOL!! Call me a plant snob but dame's rocket, red valerian, rose campion, honesty (Lunaria annua) and forget-me-nots are more weeds than valuable garden perennials in my admittedly very personal opinion :-) They all seed so prolifically, at least here in the PNW, that once planted you will be roguing out seedlings forever unless you want your entire garden inundated with them. When I was a buyer for a local nursery, these were plants I never brought in or offered for sale. Kinda like selling dandelions in my book............

One can also deadhead.

I wasn't arguing with you, floral :-) Only commenting on how these plants behave in my area and why I was not fond of them. Perhaps it's the designer in me but I dislike rampant self-seeders. I want to decide what goes where :-) And the vast majority of my client base are not avid gardeners and have no idea what 'editing' or 'deadheading' involves - they barely know how to weed!! - so when I encounter them, the plants have already made major inroads into taking over a garden.