The name means glittering but the name is also one of great confusion in the literature. Many of the plants described as splendens are in fact thunbergii. A very popular plant Allium splendens kurilense is also a form of Allium thunbergii in much of the trade.
You can recognise true thunbergii as it is very dwarf, has very narrow grassy, or thread-like leaves and it flowers late in the autumn.
The true Allium splendens has taller stems that are clothed in rough-edged linear leaves of blue-green below dense hemispheres crowded with rose pink flowers, each of which has a purple stripe on the petals.
A tolerant plant for the garden – anything from cool and moist to hot and dry is fine.