Striking blooms that are both large and colorful make hydrangeas an excellent choice for a garden plant. With several hydrangea types to choose from, you can mix and match these plants to create a display of all the available bloom colors.
There’s one problem though, hydrangeas can vary in size based on their type. So, knowing how big hydrangeas get, can help you choose the ones that are comparable in size to create a more uniform hedgerow or simply to avoid extreme variations in size.
Below you can read about the height and spread of the different types of hydrangeas as well as some tips on how to get your hydrangeas to grow faster or keep the ones that grow too fast, smaller.
Hydrangea Height & Width
In the table below I’ve summed up the maximum height and width of the six types of hydrangeas that are grown in North America:
|Mountain hydrangeas||48 inches||48 inches|
|Bigleaf hydrangeas||120 inches||120 inches|
|Climbing hydrangeas||600 inches||72 inches|
|Smooth hydrangeas||60 inches||60 inches|
|Panicle hydrangeas||180 inches||144 inches|
|Oak-leaf hydrangeas||96 inches||96 inches|
As you can notice, most hydrangeas will spread as much as their height is, except for climbing hydrangea varieties and panicle hydrangeas that have a smaller spread compared to their height.
This can give you an idea of the space you need to allocate in your garden to these plants, and which hydrangeas will be most suited for your garden.
Growth Rate of Hydrangeas
The growth rate of your hydrangeas is contingent upon many factors including climate, sun exposure, watering, and fertilizing.
Hydrangeas are classified as rapid growers, with some varieties growing an average of 25 inches per year until they reach maturity. Other hydrangea varieties, such as the Hydrangea paniculata can grow up to 2 feet per year.
Some paniculata varieties qualify as tree forms, having canopies of 18 to 20 feet wide and reaching heights of 10 to 15 feet.
When you’re planning your garden, it’s important to know ahead of time the size a given hydrangea cultivar can reach, especially that some varieties can quickly fill out the space they’re allocated.
This will allow you to allocate enough space for it in your garden, or simply choose a smaller variety if you don’t have enough space.
Speed Up Hydrangea Growth
Let’s assume that space isn’t an issue in your garden and you welcome hydrangeas reaching their maximum size. If you want your hydrangea to grow faster, there are a few ways to get there.
The tips below will not only speed up growth, but they will also help your hydrangea produce more blooms:
- Find the ideal location for your hydrangeas based on light requirements (e.g., plant panicle hydrangeas in full sun or afternoon sun or smooth hydrangeas in partial shade)
- Keep hydrangeas well hydrated especially during drought or high heat
- Make sure to plant in a location with well-draining soil
- Amend soil with compost and organic matter (it adds nutrients to the soil but also helps keep the soil moist for longer)
- Fertilize hydrangeas at least 2-3 times a year during the growing season
- Prune correctly based on whether the plant blooms from new wood or old wood
- Deadhead hydrangea blooms as blooms fade away to promote repeat blooming
As you can see there are no quick rules to make your hydrangeas grow faster. You simply need to offer your hydrangea ideal growing conditions and help it along with watering, compost and fertilizing, so that it can maximize its growth.
I mentioned how you need to be careful when pruning hydrangeas because some will only bloom from old wood and if you snip those down, you may be forced to skip a season of enjoying blooms on your hydrangeas.
Although hydrangeas don’t require annual pruning, there are times when a little pruning is necessary, either to cut back on its size a bit or to reinvigorate a hydrangea bush that is doing poorly.
First, you need to determine whether your hydrangea variety blooms on old wood or new wood.
Here’s a quick recap of hydrangea types based on blooming pattern:
|Mountain hydrangeas||on old wood|
|Bigleaf hydrangeas||on old wood|
|Climbing hydrangeas||on old wood|
|Smooth hydrangeas||on new wood|
|Panicle hydrangeas||on new wood|
|Oak-leaf hydrangeas||on old wood|
Now that you know which hydrangea blooms on old wood and which blooms on new wood, the pruning rules are simple:
Hydrangeas that bloom on new wood (i.e., new growths) should be pruned in late winter or early spring or in fall as they enter the dormancy phase.
Hydrangeas that bloom on old growths should be pruned only after flowering. Cutting old woods down in fall or early spring will have you looking at a bloomless season.
How to Keep Hydrangea Bush Small?
Sometimes it’s a challenge to keep hydrangeas at a reasonable size. If conditions are favorable in your garden, hydrangeas will quickly take up all available space until they reach their expected size.
If you may have miscalculated the space allocated for your hydrangeas and moving them is not really an option for you, there are a few things you can do to manage their size.
Hydrangeas that grow on new wood can be pruned back to the ground in late fall or early spring. You can also pinch out the tips of new growths to encourage bushier growth.
With old wood hydrangeas, wait until they’re done flowering in midsummer and simply cut one-third of the longest, thickest stems back to the ground, but do so before they set buds in early fall.
Now that you know what size to expect from the different types of hydrangeas, which hydrangea blooms from old growths and which from new ones, and how to prune the different types of hydrangeas, you can plan your garden accordingly.
Remember that growth rates and size are contingent on many factors and even though a hydrangea can reach 15 feet, it doesn’t mean it will do so if conditions aren’t favorable.