Explaining Hydrangeas

If you time it right, you can start the hydrangea season with Hydrangea arborescens (smooth hydrangea) and finish it with Hydrangea paniculata (panicle hydrangea), and have those big, showy blooms from early June until fall. Easier said than done, right?

Hydrangea macrophylla 'Nikko Blue' an old, mop-head favorite, this one blooms on old wood, which means you prune after blooming, not in fall or early spring because you'll cut off your blooms. Zoned 5-9 it can still get nipped by our late spring frosts, so cover when that happens. The blooms are blue, but in a more alkaline soil will have a pink hue. Needs afternoon shade, gets 4-6' x 4-6'. Makes a great cut flower. 

This show-stopping, summer-blooming shrub can be confusing for home gardeners. Why doesn't it bloom? When do I prune? How much shade or sun do they need? Why did I buy a pink one and end up with a blue one? Why are they so hard to grow?

There are many hydrangea species and guess what? Some require shade, and some require sun, some bloom on old wood, some on new wood. That meams the first and only step to growing hydrangeas is knowing which one is in your landscape and what makes it thrive.  

The most popular hydrangeas are listed below with a summary of the cultural needs of each one. If you still aren't sure which one is your's, take a picture of it in bloom, and the staff at the store will identify it for you. Sometimes, all we gotta do is ask. 

Hydrangea macrophylla 'Wedding Gown' or 'Dancing Snow' is a lacecap hydrangea with a double bloom. It is the purest of white, and resembles a wedding bouquet when in bloom. It is a smaller shrub with a height of only 3' but a spread of up to 5'. It prefers morning sun, afternoon shade and because it blooms on new wood, it can be pruned in spring, although pruning right after blooming is recommended.

1. Hydrangea macrophylla

Hydrangea macrophylla 'Horwack' or Pistachio hydrangea is taking the color of macrophyllas to new hues. Green turning dark pink and deep red, this shrub stays smaller and is a mophead (3' x 4-5'). 

  • Common name: Mophead, big leaf, or French hydrangea (different names for the same plant), and lacecap hydrangea. 
  • Bloom type: Large, globe-shaped blooms, hence the name mophead. Lacecap hydrangeas form a flat disc of flowers.
  • Bloom color: White, pink, blue, or purple. It can change color depending on soil type.
  • Bloom time: June/July
  • Sun/Shade: Morning sun until 1-2, then afternoon shade.
  • Zone: 5-9
  • Water: These are thirsty plants whose "big leaves" will wilt on a hot summer day, but perk up quickly after watering. 
  • Pruning: The best way to maintain them is to cut to the first pair of buds below spent blooms immediately after blooming. The older varieties like 'Nikko Blue' bloom on old wood, so if you prune in late fall or early spring, you just pruned your blooms off. 
  • Fertilize: Use Holly Tone in early spring, and a bloom booster (Rose Tone is a good choice) again in May, June and July for bigger blooms. Follow instructions on the fertilizer bag.
  • Because these primarily bloom on old wood, when the late spring frost comes, be sure to cover the plants to protect sensitive buds. 
  • Color can change from blue-to-pink or vice versa depending on soil conditions. Acid soils maintain a blue color while more alkaline soils a pink color. Using sulfur helps keep blooms blue, or lime helps keep blooms pink. 

The newer series of hydrangeas like Endless Summer, All Summer Beauty, and Let's Dance, are zoned 5-9, and bloom on old and new wood. (Each one of these is a series with several new cultivars in each series. EX: Let's Dance 'Starlight.') Because these hydrangeas bloom on both old and new wood, a late spring frost doesn't kill all of your season's blooms, and bonus, you get repeat blooms. Pruning these newer cultivars can be done anytime, but if you do so in spring, wait to remove dead wood until all leaves have pushed out. Morning sun, afternoon shade is still best, and the same applies with watering and fertilizing. 

2. Hydrangea Arborescens

Hydrangea arborescens 'Annabelle' is an old favorite. It grows 3-5' x 4-6' and can flop when it rains. Pruning hard (cut back to 12") in late fall or early spring helps to encourage strong stems and bigger blooms. It blooms on new wood. Newer cultivars like 'Incrediball' and 'Invincibelle Spirit' have bigger blooms (basketball size) and stronger stems. 

Hydrangea arborescens 'Invincibelle Spirit II' is pink and supports the research to end breast cancer. Check out how this hydrangea helps support this cause. 

  • Common name: Smooth hydrangea,  and it's famous for the 'Annabelle' hydrangea and more recently, the 'Incrediball' or the 'Invincibelle Spirit' (the first pink smooth hydrangea).
  • Bloom type: Its blooms are large, and globe shaped.
  • Bloom color: White or pink, and it doesn't change color with soil conditions.
  • Bloom Time: Early June/July through fall
  • Sun/Shade: Full sun, slight shade 
  • Zone: 3-9
  • Native Plant to North America
  • Water: Thirsty plants especially when establishing. Leaves will wilt in hot sun without water.
  • Pruning: Cut back by 1/3 in early spring to encourage strong stems and large blooms.
  • Fertilize: Over fertilizing can cause floppy plants. Fertilize once a year in early spring with Rose Tone.

The newer cultivars like 'Incrediball' (flowers the size of a basketball) have stronger stems, and 'Invincibelle Spirit' is pink. Both prefer full sun and will re-bloom throughout the season.

3. Hydrangea Paniculata

Hydrangea paniculata 'Limelight' has been a best seller for years. It grows 6-8' x 6-8' and its lime blooms fade to pink. It's cone-shaped blooms are full and make great cut flowers. This is an easy hydrangea for beginners. 

  • Common name: Panicle hydrangea.. Peegee hydrangeas and 'Limelight' hydrangeas fall into this grouping. 
  • Bloom type: Large conical shaped blooms. 
  • Bloom color: White, or lime green fading to pink or dark red.
  • Bloom time: July/September into fall
  • Sun/Shade: Full sun
  • Zone: 3-9
  • Water: Water well while establishing but it isn't as sensitive to dry days as the smooth hydrangea or mopheads.
  • Pruning: Blooms on new wood, cut back 1/3 in spring, but don't overdo, interior stems help hold up heavy blooms.
  • Fertilize: Once a year in early spring with Holly Tone or Rose Tone is sufficient.

Some of the newer cultivars like 'Quickfire' and 'Fire and Ice' bloom earlier in the season to give longer bloom in the garden.

4. Hydrangea quercifolia

Hydrangea quercifolia are good hedges or border plants. They are a nice transition between the landscape and the woods. Suckering shrubs they can reach heights of 5-8' x 5-8' though smaller cultivars like 'Munchkin'  (3' x 3') are available, too. 

  • Common name: Oak leaf hydrangea, because leaves look like oak tree leaves.
  • Bloom type: Large, pyramidal shaped, open panicle blooms.
  • Bloom color: White, fading to pink.
  • Bloom time: June/July into fall
  • Sun/Shade: Full sun to part shade.
  • Zone: 5-9
  • Water: Does not like wet feet, and can handle drier conditions. 
  • Native, stoloniferous shrub with exfoliating bark.
  • Pruning: This one blooms on old wood, so prune immediately after blooming.
  • Fertilize: Use Holly Tone in early spring. Once is sufficient.

This list doesn't include all the hydrangeas, (there's the climbing hydrangea, the mountain hydrangea, and more), but it gives a good start to understanding and including them in your garden. If you have questions, now that the store is "hydrangea haven," just ask someone for help. And the answer to that first question, Is it okay to plant them now, is YES!

Written by Cinthia Milner, garden coach, and blog writer.

Urn with hydrangea flowers in banner created by floral designer, Cynthia Gillooly.

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