You can use the label formatter function option to format the labels any way you want:
xAxis: {
categories: ['Bla bla bla label, bla bla Bla bla bla label, bla bla Bla bla bla label Bla bla bla label, bla ', 'Bla bla bla label, bla bla', 'Bla bla bla label, bla bla', 'Bla bla bla label Bla bla bla label, bla bla Bla bla bla label, bla bla, bla bla', 'Bla bla bla label, bla bla', 'Bla bla bla label, bla bla'],
labels:{
formatter: function(){
if (this.value.length > 10){
return this.value.substr(0,10) + "...";
}else{
return this.value;
}
}
}
},
Updated fiddle here.