I have this growing under a hawthorn tree in the corner of the garden and while it usually flowers quite well it seems to be a big straggly. Is it worth trying to prune it a bit to make it denser? If so when and how much.
Which plant, the Hebe or the Potentilla?
Not a Hebe I would think the Chinese lantern tree is a crinodendron, sorry about spelling. It does tend to grow quite loose.
Yes it is a Crinodendron.
Pruning won't make it much denser but will help a little. It wants to grow into a small tree really, mine are about 10 feet tall after pruning about 10 years ago. They are evergreen and can be pruned at any time of year. I think I did mine in Spring but Autumn would be fine too. Mine are now seeding and also have next year's flowers growing too. Pruning will therefore lose next year's flowers but they should grow strongly again.
Crinodendron hookerianum is native to Chile and can get quite large. Lovely in flower and next years flower buds should be visible around now. They are on a pendulous stalk about the size of a finger nail.