Essentially, deadheading is just a fancy way of saying "removing dead flowers" - and trust us, it makes a huge difference in the overall appearance of your plant. By getting rid of those wilted blooms, you're encouraging your hydrangea to focus its energy on producing new, healthy flowers instead of pouring all its resources into seeds.
But why does it matter, right? I mean, won't the plant just naturally drop its dead flowers anyway? Well, kind of - but think of it like when you're trying to get your car to run more efficiently: you want to make sure it's not wasting any extra energy on unnecessary stuff, like hauling around a bunch of dead weight (literally!).