Apparently, the winter had been so mild that the branches hadn't frozen back. It bloomed several weeks ahead of its pruned garden mates. If you're confused about what to prune back when, just remember it's safe to prune after a plant has flowered. For instance, now's it safe to prune summer flowering shrubs such as the rose of sharon, butterfly, etc. It all has to do with whether the plant blooms on new growth or last year's growth.
Hydrangeas are especially tricky and vary depending on the variety.
Assessing drought and winter damage . Damage to perennials is readily obvious. To assess a plant's health, look at its crown for signs of life. Some plants may need replacing. Trees and shrubs may suffer the lingering effects of a drought for years to come.