Online information can be a great help or a huge hindrance.
Browsing the internet the other day, the title of an article caught my eye: It’s Time To Prune Your Hydrangeas. Well, I thought, on one hand that’s true, but on the other hand it’s false. The reality is that the kind of hydrangea you have determines when and how you prune it, not a blanket command from the internet.
Hydrangea is the name (the genus) for a large group of related plants. World- wide, there are 79 identified types of hydrangeas, only six of which are commonly used in gardens here in the United States. Of those six varieties, two are native plants while the other four are introduced from Asia. (To be precise, there are actually three native hydrangeas, but one is not commonly used in landscape design.)
When you originally purchased your hydrangea, there probably was a tag that featured the name Hydrangea. Following the name hydrangea, there was a second italicized name that was actually more important because it identified the particular type, or species, of hydrangea you were adding to your garden. The species of a plant determines its unique characteristics such as leaf size and shape, height, bloom characteristics and best pruning techniques, as well as its environmental needs.
As a general rule, the six common types of hydrangeas can be divided into two general categories – those that bloom on old wood and those that bloom on new wood. When a plant is said to bloom on old wood, it means that “the buds for the next year’s blooms are formed at the end of the current growing season.” (Proven Winners) If you cut an old wood plant back in the spring, you will reduce or even eliminate flowers for that season. An old wood plant should be pruned immediately after flowering finishes or in early fall.
A “New Wood” plant means that blooms will appear on newly emerging stems. These plants need to be pruned in late winter or very early spring. Cutting back or removing some of the old growth can encourage vigorous, new growth. Experts advise cutting back new wood plants by ½ to ⅓ and completely removing any weak or rangy branches.
Whether pruned at the end of the flowering season, or in the early spring, hydrangeas should be cut at a 45 degree
angle slightly above a node.
Sharpened bypass pruners, or pruners that have two blades and function like scissors, are usually the only hand tools needed to prune hydrangeas, although loppers can be useful on thick, woody branches of climbing hydrangeas. Don’t use anvil pruners 
(single bladed pruners) because they can easily crush the plant’s stems, severely damaging it over time. Aggressive pruning can lead to fewer flowers that are larger and more dramatic.in appearance. Less aggressive pruning can give more flowers that are smaller in size.
If you aren’t sure which type of hydrangea you have, the chart below may help you identify your plant and decide whether it needs to be pruned now like the article insisted, or whether you can just sit back and relax!
OLD WOOD BLOOMERS
BIG LEAF/ MOPHEAD/ FRENCH HYDRANGEA
Hydrangea macrophylla
- Zones 5 -9 (winter protection 4-5)
- Part to full shade
- White, pink, blue, purple or red blooms
- Consistently moist soil
- Blooms June to October
- Some varieties are reblooming/prune any time
OAKLEAF HYDRANDEA
Hydrangea quercifolia
- Zones 5-9
- Full sun to part shade
- White to pink blooms
- Blooms July to September
- Native plant
MOUNTAIN HYDRANGEA
Hydrangea serrata
- Zones 6-9
- Part shade
- Pink or blue blooms
- Blooms June to August
- Smaller variety at 2-4 feet
CLIMBING HYDRANGEA
Hydrangea anomala ssp. Petiolaris
- Zones 4-6 &8
- Part to full shade
- White blooms
- Blooms May to July
- Can reach 40 feet
NEW WOOD BLOOMERS
SMOOTH HYDRANGEA/ANNABELLE
Hydrangea arborescens
- Zones 3-9
- Prefers part shade
- Tolerates full sun with moist soil
- White to pink blooms
- Blooms June to September
- Can be pruned to the ground
- Native plant
PANICLE/ PEEGEE HYDRANGEA
Hydrangea paniculata
- Zones 3-8
- Full sun to part shade
- White, pink blooms
- Blooms July to September
- Extremely winter hardy
