When and how far back should I prune my daisies or should I prune them at all?
Most people dead-head shasta daisies to encourage more bloom. This clump-forming plant does not need pruning, per se, but may benefit from division every few years. This gives you the chance to discard old, non-productive growth and work some compost into the soil. At the end of the flowering season, cut all stems down to the basal leaves. Leave the bottom leaves intact and they will provide some winter protection. Oxeye or field daisies, Leucanthemum vulgare, is invasive in the US and should not be grown. There are other types of daisies. Check out this website's pages on daisies: https://www.gardeningknowhow.com/search/?q=daisy%20care