How did Your Hydrangeas Bloom this Year?


So how did your Hydrangeas bloom this year?

One the most common questions I get, is "Why won't my Hydrangea bloom." Of course they're talking about the beautiful species called Hydrangea macrophylla (Big Leaf Hydrangea).

.... [Not sure what type of Hydrangea you have? Click here]

This plant is extremely popular because it is the most colorful of all the species. This plant can be categorized into two main groupings: Mopheads (snowballs) and Lacecaps. The Mopheads are large round clusters of sterile flowers and the lacecaps are flat heads composed of both fertile and sterile flowers. The mopheads are the most popular because we tend to love the gaudy. The lacecaps are gaining in popularity and are considered by many, including myself, to be even more beautiful because of their delicate looking nature.

The key message here is that Hydrangea macrophylla is it sets its flower buds in the fall when night temperature fall below 60F/16C. Thus the flower buds must survive the winter if they are to mature into big beautiful flowers the following summer. [We call this blooming on old wood.] This is the crux of the problem - a hard winter, an early fall freeze, a late spring freeze, or untimely pruning will damage the flower buds and result in a loss of flowers.

So what is a person to do if they want to be successful with Hydrangea?

1) Understand how and when to prune

Big Leaf Hydrangea does not require much pruning once established, but proper pruning is critical if expect to see flowers.

The best time is in early to mid-July. Prune back any non-flower stems back to about six inches from the ground. This helps to produce short stems which keeps the next crop of flower buds close to the ground where they can be more easily protected from winter damage. It is critical that you cease pruning by the end of July. This allows time for the new flower buds to form and harden off prior to winter.

2) Shut the plants down before winter

Hydrangeas will continue to grow as long as there is ample water, fertilizer and warm weather. Later season growth is tender growth and more prone to winter injury, so useful to shut the growth down before winter comes. In late summer and fall, stop fertilizing and cut back on the water. Don't worry if the plant looks severely wilted, just provide enough water for the plant to survive. This will slow down the growth, help to induce flower bud formation and make the plant less susceptible to an early freeze.

3) Mulch and Protect

In late fall, mulch the base of your plant with six to ten inches of bark or peat moss. This will protect the buds on the short stems (the ones you pruned in July). Apply the mulch after the onset of cold weather but before the temperature falls below the teens. This mulch will be removed or spread out in the spring after the danger of frost has past.

4) Grow Varieties that Bloom on both Old Wood and New wood [rebloomers]

Within the last ten years, varieties have been developed that make buds in both the fall [typical], and during the summer [atypical]. Or putting it another way, they flower on both old and new wood. This means that even if the flower buds are injured in the winter, new buds and flower will form the next summer. This is great news for those of us who live in cold climates.

The cultivars 'Endless Summer', Let’s Dance Moonlight, Let’s Dance Starlight, and 'Forever and Ever' have the ability to bloom on old and new wood alike. These are great selections for the Midwest where it is hard to get Hydrangea to bloom. 'Endless Summer' was the first rebloomer to hit the market, while the Let's Dance series is the newest generation of rebloomers. The Let's Dance series has superior flower color, overall substance and thicker, glossier leaves. They are also less likely to die to the ground in the winter.

Now I know that many people were disappointed with the Endless Summer Hydrangeas this year.

We had a long warm spell in late winter followed by weeks of freezing weather that knocked many Hydrangeas back to the ground. As a result, the old wood buds were killed, and we lost the early-season flowers, even on the rebloomers.

Keep in mind that, even with these new varieties, you get a much better flower display if the old wood buds survive the winter. Sure, if your plants die back to the ground in the winter, you will still get flowers, but they appear later in the season and there are typically fewer flowers overall. So - it still pays to prune properly, keep the buds close to the ground and protect these buds with mulch.

- Another Tip for Rebloomers Like Endless Summer -

If your Endless Summer dies back to the ground in the winter, forcing growth will deliver more flowers and sooner. Endless Summer and other rebloomers have to put on a certain amount of new growth before they will make new buds and flower. So it pays to give these plants extra fertilizer and water to push the growth. Miracle Grow once a week after any danger of frost does the job.

For some people, rebloomers are not the best choice.

If you live in a mild climate where big leaf hydrangea blooms reliably there is no advantage in growing rebloomers. You lucky people have a wonderful array of varieties to choose from, many with superior foliage and flowers. For example - consider the new dwarf cultivars sold under the CITY LINE series. These compact plants form a neat compact plant that is covered with blooms. They also have very vivid flower colors.

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(If you live in a very cold area consider Hydrangea paniculata (Limelight, Pinky Winly, Little Lamb and Quick Fire) and Hydrangea arborescens (Invincibelle Spirit and Incrediball. There are many great new vareities and they are pretty much fail proof.)


----------------Back to Hydrangea macrophylla

Flower color - How to change Flower Color

Another interesting attribute of this plant is that its flower color may change depending on soil p.H.. It is not the p.H. itself that changes the color, but it is the availability of aluminum ions that directs the color. Aluminium has greater availability in acid soils thus the blooms turn blue in acid soils. If the soil is either basic [alkaline] or high in phosphorous, the aluminium is tied up and flowers tend to be pink. The degree of color change is dependent upon the amount of aluminum ions available and the cultivar itself. It should be noted that if you are growing in a container your soil mix you may not have much aluminum availability even at low p.H. levels. Aluminum sulfate treatments would then become necessary to get blue flowers. If you fertilize your plants be aware that you will tie up the aluminum with high levels of phosphorous.
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16 comments:

  1. Monica8:58 AM

    Thank you! This is the best accessible piece that I have seen on growing H macrophilla.

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  2. My husband and I still argue about when to prune. This year, he took a pair of hand pruners to them in the spring and I almost had a heart attack. Mine have been in the ground for 2 years now and they're doing ok, but I wonder about that early pruning.

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  3. Mike O'Hara5:27 PM

    Thanks, your article was very informative. especially about cutting back water and fert. in fall to help produce flower buds.
    For the past 2 years I have been wrapping my hydrangeas in burlap, erecting cages around them and filling the cages with leaves to protect them in winter. this past season 42 of 44 bloomed.
    I'm in zone 6b southeastern PA.
    Many years I had very few or no blooms.
    Mike O'Hara

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  4. Great advice, but I think there are much better fertilizers then Miracle Grow.

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  5. Looks like you are bringing us some exciting new hydrangea varieties! Your comments about gardeners in milder climates who might not wish to grow rebloomers may be true for some areas. But I've found that most southern locations (such as South Carolina)that tend to have mild winters but cold springs are constantly being hurt by late spring freezes and frosts. Most years, when few hydrangeas are blooming, some rebloomers (remontant) would be greatly enjoyed!

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  6. I second the comment about Miracle-Gro. I actually can't believe you said that. Let's give compost or well-rotted manure a plug instead.

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  7. Thanks for the great advise Tim. I agree with the comment on the Miracle Grow. There are far superior fertilizers then it. I had the best year for my hydrangeas. The real damage this year was from the heavy snow fall. It broke many of my stems from the weight. My Endless Summers were gorgeous for the first time in years. Bits of Lace finally bloomed, Twist and Shout was fabulous. Even my Little Honey bloomed. The only one that did not flower was Fuji Waterfall and it got snow damaged. I have been burlaping some of my more exposed plants and covering with frost clothes when we have freeze or frost warnings. It seems to have done the trick. I am going to try the pruning tips this year and will let you know the results. Thanks again. I enjoy reading your blog.
    GardenGal

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  8. Just a word for people who want to grow hydrangeas in harsher climates. Here in Sundridge, Ontario (zone 3b) H. paniculata grows slowly but flowers well in full sun, no winter protection needed.

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  9. Tim, my Endless Summer hydrangeas did wonderfully here in VA in spite of all the snow we got this past winter. In fact, I think its because of the snow that they became "shrubbier" and more dense and full than usual. I think the snow insulated the buds up and down the stems from the cold air, and thus I had growth coming not just from the crown, but from the stems as well. Additionally, I have pink, purple, and blue on the same flower heads!

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  10. Lucky us! We live in zone 5, didn't pay much attention to pruning and lucky us we had TONS of blooms this year on both our Endless Summer and Pinky Winky's and a macrophylia lacecap (whose name is unknown to us). Just dumb luck I guess! Your article is terrific though and I will use the info in the future. Thank you for sharing!

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  11. No doubt - this was a great year for hydrangeas here in Michigan. We had constant snow cover all winter long. Spring was a bit wacky - we did have some very hard frosts but our hydrangeas seem to have escaped damage while my Rose of Sharon had all there leaves frozen off.

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  12. By the by, your article is about pruning young Hydrangeas, you don't mention how to prune older, established Hydrangeas for bloom. Is it correct to cut off all of the flowers before fall? If an older branch does not flower do you cut it back 6" to the ground? If the plant is under great heat/sun stress are less flowers better for it (I cut off many blooms this year because there were too many for the plant to survive the heat wave). Was that correct? Please advise.

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  13. Prune established plants as little as possible. Remove the old flowers in late fall or early spring. Not every stem produces a flower so you can prune them back hard without sacrificing the flower. (Do so before July 1 so that plant can grow, and set flower buds before fall). This creates more stems and thus more flowers. Pruning these stems low make it easier to protect them (snow / mulch) and the flower buds. There should be no reason to remove good flowers. If heat is a problem - then the plant is 1) in too much sun 2) not getting enough water or 3) it is a poor variety.

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  14. Couple questions for you, Tim:

    1) When are we going to see a remontant lacecap with some of the charm and style of the older varieties? Starlight's nice, but not gasp-worthy, like some of the serratas.

    2) Will oakleaf's ever get a big push? These wonderful shrubs are so underappreciated. Snowflake is absolutely incredible.

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  15. I think you will see that Let's Dance Starlight gets better every year. With maturity the flower size rivals those in the Teller Series. We have some pretty cool reblooming serratas in the pipeline, so I think these will be out in the next few years. Plus they have better stem hardiness than Hyd. marcrophylla. I have also seen some very good oak leaf breeding. So there is a lot of good plants coming.

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