Liatris aspera is a perennial wildflower in the aster family that bears erect, unbranched stems topped with dense, purple, button-like flower heads. Plants typically reach 0.3–1.8 m tall and carry numerous narrowly lanceolate leaves along the stem. Flower heads open from the top downward and are produced July to September. It is native to central and eastern North America and occurs in prairies, glades and dry savannas.

Rough Blazing Star (Liatris aspera) flowers July to September with purple, button-like heads that attract butterflies and birds.

https://en.wikipedia.org/wiki/Liatris_aspera

Liatris aspera

Rough Blazing Star | Liatris aspera

Liatris aspera 'Alba' is a perennial in the Asteraceae valued for its summer flower display. Native to several US states including Missouri, Georgia and Kansas, it suits open, well-drained sites. It flowers from July to September and prefers full sun on sandy or loamy soils with dry to medium moisture. Use it in wildflower plots, prairie restorations or for cutting.

White Blazing Star (Liatris aspera 'Alba') blooms July to September and favours full sun with well-drained, sandy or loamy soil.

Liatris, commonly known as gayfeather and blazing star is a genus of flowering plants in the tribe Eupatorieae within the family Asteraceae native to North America. Some species are used as ornamental plants, sometimes in flower bouquets.

Liatris aspera 'Alba'

White Blazing Star | Liatris aspera 'Alba'

Liatris pycnostachya is a perennial in the Asteraceae grown for its tall, erect flower spikes. It produces pink to purplish-pink flower heads from July to September. The species originates from central and eastern USA and favours sunny, well-drained sites. Plants perform best in sandy or loamy soils with a neutral to slightly acidic pH.

Kansas Gay Feather (Liatris pycnostachya) produces upright pink to purplish-pink flower spikes from July to September and suits sunny, well-drained sites.

https://en.wikipedia.org/wiki/Liatris_pycnostachya

Liatris pycnostachya

Kansas gay feather | Liatris pycnostachya

Liatris spicata 'Alba' is a herbaceous perennial in the Asteraceae prized for its white flowering spikes. It grows to about 0.6 m high with a 0.5 m spread and flowers from July to September. Plant it in full sun on sandy or loamy soils that stay moist but drain; it also tolerates wet conditions. Stems are useful for cutting and it suits borders and pollinator planting.

White Blazing Star (Liatris spicata 'Alba') produces white blooms July to September and suits moist sandy or loamy soil in full sun.

https://en.wikipedia.org/wiki/Liatris_spicata

Liatris spicata 'Alba'

White Blazing Star | Liatris spicata 'Alba'

Liatris spicata 'Kobold' ('Gnome') is a compact perennial that bears upright spikes of deep purple flowers. It grows to about 0.6 m tall with a spread near 0.5 m and flowers from July to September. Plant in full sun on sandy or loamy soils that remain moist but are well drained. It is suited to borders, pollinator plantings and cutting for arrangements.

Dense Blazing Star (Liatris spicata 'Kobold' ('Gnome')) flowers July–September and suits sunny, moist sandy or loamy soils in the UK.