How to Prune Hungarian lilac?
Cut flowered growth back to strong young shoots below, removing up to a fifth of old stems near the base each year. Prune immediately after flowering.

Hungarian lilac · Syringa josikaea
Also known as: Lady Josika's lilac
Easy to grow in good light, in moist but well-drained soil. It likes neutral to alkaline soil and thrives in chalky ground.
Cut flowered growth back to strong young shoots below, removing up to a fifth of old stems near the base each year. Prune immediately after flowering.