How to Prune greater musk mallow?
Prune back flowered stems in the autumn

greater musk mallow · Malva alcea
Also known as: hollyhock mallow; vervain mallow
Prefers to grow in light, well-drained, moderately fertile soil in full sun. It is likely to need support especially if grown on rich soils - see staking perennials. Can be short-lived
Prune back flowered stems in the autumn