I have (had) a beautiful sweet broom plant, growing contently in it's place. We have a new yard and have been planting and creating our rose beds. This sweet broom is part of this bed. We recently mulched...mainly for the roses. Got up one morning and my sweet broom was "deader than a donut". Dry and brittle. I read that they don't require an intense amount of water...which we hadn't been doing. The only thing different was the mulch. Does anyone know what could have happened?