There's nothing more disconcerting than seeing plants that you've nurtured, suddenly collapse and start to die back – especially if it followed by complete death!
Shoots, stems and leaves may die back for any number of reasons – including waterlogging at roots, drought conditions, frost damage, very hot weather, disease problems or general lack of plant nutrients such as potash or phosphates.
Wilting at the tip of the shoots gradually moves down the stem and to the rest of the plant.
Treatment and control
Obviously work out what conditions have caused the collapse and die back and do everything to remedy them. If done quickly, the plant may recover.
Cut back affected stems and growth below the dead area, but just above a bud or leaf joint. Don't be tempted to do this quickly, in case the plant makes a recovery. For instance, frost-damaged shoots may recovery and start re-growing as late as June or July.
Feed the plant in spring and summer with balanced, liquid plant food to encourage strong new growth.