Hydrangeas are beautiful perennial plants prized for their luscious, spherical blooms that add sophistication to gardens. With so many varieties to choose from, gardeners can find any size, color, or style to fit various types of landscapes. Most hydrangeas prefer part shade and fairly moist soil, which makes them a rare shade plant that boasts such extraordinary flowers and hues. Don’t fret if you have a spot to fill in full sun, as there are hydrangeas for any location. Read on to learn about how to care for hydrangeas, including how to plant hydrangeas, how to grow hydrangeas, and how to divide and transplant them.
The Six Main Hydrangea Varieties
1. Big Leaf Hydrangeas
Big Leaf Hydrangeas are one of the most common of the six main hydrangea varieties. Commonly referred to as French hydrangeas, hortensias, or mopheads, these plants have the traditional full, fluffy looking blossoms with many smaller flowers making up one large "head" that extends upright from a singular stem
These will fill in empty spaces wonderfully, growing six to ten feet, with little pruning or fuss needed to keep plants blooming from June until October in zones 5-11. Their color will depend on your soil composition: blue hues form in acidic soils with a pH under 6.0, whereas pinks occur in alkaline soils above 7.0 pH.
Deep red varieties are also available. You can amend the soil with either aluminum sulfate to lower pH or dolomitic lime to raise pH to achieve the respective colors with these varieties. They like part to full shade conditions with moist soil, making them excellent choices in any heavily treed or shady area of the garden.
2. Panicle Hydrangeas
Panicle hydrangeas are the most winter-hardy plant, growing in zones 3-8. They can be planted in full sun or part shade, and may reach up to fifteen feet tall. They can be identified by their upright, cone-shaped blooms that start off green and turn a beautiful white from midsummer to early fall.
They need pruning either before or after blooming in the winter or early spring to encourage abundant flowering. Some common names at garden centers are ‘Limelight’, ‘Bobo’, ‘Grandflora’, ‘PeeGee’, and ‘Pinky Winky’.
3. Smooth Hydrangeas
Smooth hydrangeas also produce white flowers, but these are more modest than the first two, offering lacy, delicate blooms that still grow somewhat large and rounded, just not as bulbous. White flowers will sometimes turn a slight pinkish color, either due to the variety, or when it gets closer to fall.
Their color does not change or depend on soil pH. ‘Annabelle’ and ‘Incrediball’ are the most popular varieties, preferring part shade or full sun if the soil is kept sufficiently moist. Good in zones 3-9, they stay compact at around three to five feet, blooming at the beginning of summer up until the start of fall.
They can be pruned down to the wood every two years to keep them shapely and to support new growth.
4. Mountain Hydrangeas
Mountain hydrangeas have a much narrower growing zone between 6 and 9, and only reach four feet at full maturity. These smaller, compact plants have tinier blooms, ranging from the same blues and pinks comparable to Big Leaf varieties that intermingle with prominent, serrated, dark green leaves.
No less stunning, they offer a different approach to using hydrangeas in your garden, and perform well in planters, containers, and pots, or as smaller accents in part shade perennial gardens. Flowers bloom on old wood, unlike the previous cultivars mentioned, lasting from June to August.
They will need to be pruned after blooms are spent. Look for 'Blue Bird', and 'Tuff Stuff'.
5. Oakleaf Hydrangeas
Oakleaf hydrangeas also bloom on old wood, just like Mountain varieties, but grow to a height of around eight feet in either full sun or part shade. Good in zones 5-9, the white, purplish, or pink flowers are around from midsummer to the start of fall, and will benefit from pruning after flowers are done.
These plants provide nice fall interest as the blooms change color from a delicate white to deep red. Dark green leaves acquire the typical fall hues, turning red, orange, yellow, or even burgundy and purple. Native to woodlands mainly in Southeast US, look for ‘Ruby Slippers’, ‘Pee Wee’, and 'Snowflake'.
6. Climbing Hydrangeas
Climbing hydrangeas are the only vining variety that can cover a vast amount of distance when allowed to spread. When trained to climb heights, they can reach up to 40 feet in part or fully shaded areas. These are the earliest bloomers, with white flowers popping up in the spring and lasting until midsummer.
Happily grown in zones 4-8, light pruning is usually needed after flowers are spent to keep the vine controlled to the area you want it. Anything more drastic should wait until the winter or spring when the plant is still dormant.
These varieties are excellent for growing up trellises, arbors, fences, against or over walls, and can even trail along the ground. ‘Miranda’, 'Flying Saucer', and 'Silver Lining' are just a few to choose from.
Do Hydrangeas Need to Be Cut Back?
Cutting back hydrangeas depends on the variety you plant. "Smooth" hydrangeas are the only ones that benefit from a hard pruning (cutting back to the ground), and that’s only every other year, once the plant has been established – and still, only if you want to keep growth in check.
Other hydrangeas may benefit from heading cuts (just above buds), but again, this depends not only on the variety, but the specific cultivar, and also on how your plant is performing.
Always check the tag when buying new hydrangeas from a garden center or nursery, and if there aren’t pruning instructions, do some research. If you are being gifted an unknown variety, many websites and even free apps on your smartphone can identify hydrangeas with just a few key search words when describing their color, size, and any other information a previous owner has about them.
If you still aren't sure, you can wait a season or two and see how it's doing, as pruning isn’t a deal-breaker for most hydrangea varieties.
Should You Pick Hydrangea Flowers?
While many varieties can have their blooms cut for bouquets, not all of the varieties are bushy and prolific, so you may end up taking away any flower interest too early. Wait to cut certain varieties until they are either done blooming (flowers will die off anyway), or if you know they will benefit from pruning.
You can also freely cut flowers from mature plants that have enough blooms to spare, especially on cultivars that rejuvenate on new wood. For many of the Big Leaf hydrangeas, spent blooms lose color and eventually dry out, causing quite an eyesore amongst other healthy blossoms.
Use sharp hand shears to nip them off just under the blossom head.
Water, Light, and Soil Needs
The majority of hydrangeas need consistently moist soil, and while this also depends on the variety, there are no drought-tolerant hydrangeas. These plants will especially need the proper amount of hydration when they are in full bloom, as the energy the plant needs to create such large blossoms takes a lot of water.
If you see your plant has dried out and is sagging, give it a good soak, and watch them bounce back. These plants are fairly tough, and can handle a little neglect, but don’t test your luck too often.
If you notice brown spots on the tops of flowers, that may be an indication of the soil being too dry, or it could be sunburn and your hydrangea needs more shade protection. Always follow the directions on the tag when it comes to recommended sunlight and provide good quality, well-draining soil.
Amend with compost or manure, and fertilize species according to cultivar needs.
Can You Split Hydrangeas?
When hydrangeas are healthy, they will inevitably outgrow their surroundings or crowd out other plants in the garden, so the answer is yes!
Whether you want to divide your hydrangeas due to overgrowth or because you simply want to split up a nice specimen to gain another one, you’ll need to follow some steps for keeping the plants healthy according once again to the cultivar.
While many varieties of the mophead and lacecap hydrangeas can be successfully divided, the Nikko Blue, one of the most popular hydrangeas grown by home gardeners, seems especially receptive to division and transplantation.
This variety grows fast and needs a lot of space, so make sure to plant it in an area where it will have plenty of room to spread out.
When to Divide Hydrangeas
The best times to divide hydrangeas are in the fall when the plant is no longer in bloom, and all of its leaves have fallen. This signals that the bushes are ready to go dormant and can handle hard pruning or transplanting. The other time is in the early spring before any new growth begins, as the plant is still in its dormancy.
How To Divide Hydrangeas
Water your hydrangea the day before you want to divide or transplant it. Don’t over water or soak it, just give it a little drink. The next day, dig around the perimeter of the hydrangea bush about two feet from the main stem, using a good shovel to make sharp, deep cuts.
Work to loosen the roots from the soil as much as possible, being careful not to sever them. Remove the root ball or the primary mass of roots beneath the plant.
Keep in mind that mature hydrangeas can be particularly heavy. Tying the limbs of the hydrangea with twine or rope into sections can keep the shrub contained for easy transport, and help expose the stem when digging. Some gardeners have reported root balls as hard as cast iron. While this may be a slight exaggeration, the root ball of an established plant will be heavy and thick, so properly removing a mature one may require tough measures like using a pick-ax, or having two people attack the job.
Dividing the Root Ball
Once the root ball is out of the ground, use the shovel again, possibly with the help of a pitchfork, to divide the root ball into the number of desired sections. The bigger and heavier the plant, the better it is for dividing.
Align the blade of your shovel into the middle of the root ball, and then apply pressure to sever it into two individual shrubs of approximately equal size. From there, divide further if need be.
For most large hydrangea bushes, this will be two or four sections, although particularly large ones may be divided successfully into five or more smaller clumps.
How to Replant Hydrangeas
Always keep in mind how big your hydrangea will grow when planting them together. Give them enough space to mature without crowding each other out. While the area may look sparse at first, hydrangeas are fairly rapid growers and will fill in naturally within a year or two.
Once hydrangeas have been divided, it’s best to plant them into their new spot right away, as roots shouldn't be exposed for too long. The best time to plant your sections is when the skies are overcast, although with a little care they can be transplanted any time of day as long as they get enough water.
Prep the Hold
Dig a hole twice the size of the root ball that’s being planted and fill it partially with water. Loosen the soil and the root ball so that roots can penetrate the ground and establish more successfully. Make sure to plant no deeper than the previous soil marks on your old plant, but also not to plant it too high in the ground.
Use the topsoil you removed and take this moment to amend it with compost or composted manure to help get the new plants started. Blood and bone meal can also help when transplanting, as well: sprinkle some at the bottom of the hole and around the base of the hydrangea once it’s planted.
Add Mulch and Thoroughly Water
Once the hydrangea has been planted, add mulch, and water deeply, especially if it's hot and sunny out. Hydrangeas may droop at first, but they should perk up after a few days.
Keep watering throughout the summer or if conditions are dry, as these new plants need to get their roots deep into the ground and require lots of nourishment. Direct a rain barrel system to the new area if possible, and redirect any downspouts to the plant.
Supports for Hydrangeas
There are a few varieties of hydrangeas that will benefit from support systems. Of course, any trailing or climbing vines will need trellis or wall support, but even upright varieties may become top heavy with excessive blooms, or after heavy rains.
Certain mophead cultivars have weaker stems than others and may benefit from staking or an added circular support similar to peony cages. Ones that are kept in containers can especially benefit from these if you notice floppy flowers.
In general, healthy hydrangeas keep themselves upright easily as long as they are given enough water and have been planted in the right spot. Pruning or head cutting flowers can help with top-heavy plants.
How To Keep Hydrangeas Blooming
Deadheading, light pruning, and cutting spent flowers can help divert energy back to the plant so that it can focus on producing more blooms. Always follow tag instructions, and don’t interfere too much with newly planted hydrangeas as they are getting established. If your hydrangea isn’t producing much, the soil may be depleted. Adding compost, composted manure, dead leaves, and specific flower-based fertilizers can give your plants a boost. Patience is also required for new transplants.
Hydrangeas are one of the most unique perennial plants that gardeners adore for their stately beauty and easy care. With six main varieties to choose from, and many cultivars to boot, there's a good chance you'll be able to find something that fits your garden space. While hydrangeas don't require a lot of tending to, knowing how to plant, grow, and care for your hydrangea will ensure that you have beautiful blooms for years to come.