l have grown some Alliums and the flowers have faded, should I cut off the flowering stems?

If you want to use the heads in dried flower arrangements leave them until they are thoroughly dry before cutting them off.

However, if you do not want to keep them, they can be cleared away as the bulbs are now dormant.

They will probably have set and scattered a lot of seed and you may find that you have a crop of allium seedlings appearing next spring.