possibly last winters frost and/or this summers drought at a guess--p.s liked the plant Idents not sure the're all right but you could google the name and see :o)

this looks like either wind burn or drought, if the browning started recently, you're not watering sufficiently.

Looks like root drought to me also. This doesn't mean the remedy is to keep it constantly sopping wet either of course! A really good soak (that looks like a pot possibly 10 litres in size?) A full two gallon watering can once a week or shorter interval when it has filled the container with roots. This is the summer regime for watering. In winter, once a fortnight. Forget about any rain too, this has little effect.

Thanks. I will start watering regularly.