I have 78 digital images of Sedum spectabile saved from 2003. Here's a top 10 selection. I am vague about the names of the plants because I have bought/propagated a number of Sedums and they have got mixed up over the years!
Small Tortoiseshell and Comma on Sedum spectabile 'Brilliant' (?) August 22.
Speckled Wood on either 'Iceberg' or 'Stardust'. September 5.
Brimstone on 'Brilliant' (?) September 4.
Red Admiral on 'Brilliant' (?) August 29.
Painted Lady on 'Brilliant' (?) August 23.
Comma on either 'Iceberg' or 'Stardust'. September 4.
Peacock on 'Brilliant' (?) September 4.
Small White on 'Brilliant' (?) September 20.
Gatekeeper resting on Sedum buds. August 5.
Vine Weevil. August 27. You do not want these near your Sedums!
I think that you need a good clump of Sedums to attract the butterflies rather than having a single plant. I didn't have much success until I grouped some of my Sedums together about a year ago.
I have bought Sedum spectabile
Pink Fairy (pink)
Sedum Herbstfreude (Autumn Joy)
Sedum Ruby Glow
Sedum albo' Mediovarigatum
The top 4 above are good at attracting butterflies; the other 3 are not. Plant centres mainly stock 'Autumn Joy'. I have seen butterflies on that but I've had to watch carefully for those very rare visits. I recommend that you buy 'Brilliant' instead, which is not too difficult to find.
If a stalk of Sedum spectabile breaks off, pop it in a vase of water on the windowsill and it will root easily. This is extremely useful knowledge if you are visited by Vine Weevils. The Weevils eat notches out of the leaves but the bigger problem is that their grubs demolish plant roots fast and they adore Sedums! They are one of the major pests in British gardens now.
Plant Type: perennial
The label of 'Stardust' says "This variety of the popular Ice Plant has light green, succulent foliage and bears heads of gleaming white flowers in late summer. Very attractive to bees and butterflies. Best in full sun on a well-drained site."
Flowers in late August/early September
Height: 45-60cm (18in-2ft)
Care: Lift and divide every 3 years to maintain flowering.