Nelly Moser dying back
My mother has a Nelly Moser which she’s had for about 8 years and it used to flower quite well but she never pruned it back in spring and it was all woody stems. I pruned it back to about 15 cms in spring 2021 but since then it grows about 30 cms and then in June dies back. It did exactly the same this year, it just goes brown and brittle. Does anyone know why this happens. I was quite surprised that it started growing again this April given what had happened last year.