Explaining Hydrangeas

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. 

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 right on till fall. Easier said than done?

These glorious, summer blooming shrubs can be confusing for home gardeners. Why don't they 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?

They aren't, as a quick how-to will show. The first and only step in growing hydrangeas is understanding the different species. In other words, knowing which hydrangea is which, tells us how to grow and care for them.

There are many species of hydrangeas. The most popular ones are listed below with a summary of the cultural needs of each one.

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: The common name for these is mophead, big leaf, or French hydrangea (different names for the same plant), and the lacecap hydrangea. 
  • Bloom type: Bigleaf hydrangeas have 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 no later than 1-2, then afternoon shade is best.
  • 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, then again in May and July. This keeps blooms vigorous but don't overdo, too much fertilizer for bigleaf hydrangeas causes plant growth over blooms. Follow instructions on the fertilizer bag.
  • Because these 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. 

Hydrangea arborescens 'Annabelle' is an old favorite. It grows 3-5' x 4-6' and can flop when it rains. Pruning back by 1/3 in early spring helps to encourage strong stems. It blooms on new wood. Newer cultivars like 'Incrediball' and 'Invincibelle Spirit' have bigger blooms (basketball size) and stronger stems. 

2. Hydrangea Arborescens

  • Common name: Known as smooth hydrangea, 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, it doesn't change color with soil conditions.
  • Bloom Time: Early June/July
  • Sun/Shade: Tolerates full sun, but prefers some shade. 
  • Zone: 3-9
  • Native Plant
  • 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. Do not cut back to ground.
  • Fertilize: Over fertilizing can cause floppy plants. Fertilize once a year in early spring with Rose Tone.

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

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 is the common name for some of the easiest to grow hydrangeas. 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
  • 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.

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

Some of the newer cultivars like 'Quickfire' and 'Fire and Ice' (pictured in banner at top of blog post) bloom earlier in the season to give longer bloom in the garden.

4. Hydrangea quercifolia

  • 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.
  • 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, 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, blog writer, outside sales staff.

BB Barns serves all of Western North Carolina, upstate South Carolina and Tennessee.