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Do Hydrangeas only bloom on old growth, not new?

Posted by HighlanderNorth 6b Delaware (My Page) on
Thu, Jul 10, 14 at 20:57

This winter was cold and very snowy. Every hydrangea I have seen this season had its old above ground growth killed back, so that all of last year's stems were dead. That means none of the leaf buds ever grew, so all above ground stems had to be cut back to just above ground level.

After April went onto May, we started seeing lots of new stems growing from the base of hydrangeas, and most plants I have seen had enough new stems grow that the plants became nice and thick again. No problems.

But now that we are into almost mid July, I see no evidence of flower buds forming on any, except for a few large Oak leaf hydrangeas. That has made we wonder if hydrangeas only bloom on old, previous year's growth, and not on new growth? Summer bearing raspberries and blackberries do this as well.

I am surprised I dont know the answer to this already, from previous year's experience, but I guess I just never paid that close attention to which stems the flower buds formed on....


Follow-Up Postings:

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RE: Do Hydrangeas only bloom on old growth, not new?

99% of hydrangea macrophylla / serrata bloom on primarily old wood.

All oakleafs (quercifolia) bloom on old wood, but are more winter-hardy. Most people's oakleafs that don't have deer eat the buds in the winter time.

New wood varieties include hydrangea arborescens and paniculata, but both are primarily white with a few pinks.

Any other simple answers you may be seeking are littered throughout this forum (going back many years) and the net (there are sites completely devoted to hydrangeas).


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RE: Do Hydrangeas only bloom on old growth, not new?

  • Posted by vasue 7A Charlottesville (My Page) on
    Fri, Jul 11, 14 at 10:27

After this last Winter caused the same setback you're seeing - hydrangeas that bloom on old wood that suffered dieback won't bloom this year - many of us are looking at the "reblooming" macrophylla (mophead) & serrata (lacecap) with renewed interest. As Springwood says, most of the mopheads & serratas bloom on "old" wood - stems that are at least a year old.These set buds mid-Summer to Fall (depending on your zone & local weather) that bloom the following year. Buds can be killed by cold, as can entire branches.

Those that bloom on "new" wood - branches that grow in the current season - bypass the setback old wood bloomers can encounter. "Reblooming" varieties can bloom on last year's old wood AND this year's new branches. If the old wood buds are killed, new wood will still bloom if your growing season is long enough.

Some are calling those that bloom only on new wood "rebloomers" if new branches grow additional stems that bloom later. The fine line between "rebloom" and "extended bloom" can become confusing. If you want mopheads & lacecaps that can bloom early in the Summer on old wood & later in the season on new wood - so you will have at least one set of blooms every year - look for varieties with info about blooming on old & new wood.

Many new varieties have been & are being introduced to market in recent years. A good bit of discussion here reviews introducers' claims and personal experiences growing them in our gardens.


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RE: Do Hydrangeas only bloom on old growth, not new?

The wonderful advantage to having the 'Endless Summer' types of hydrangeas (there are now many on the market); is that when it comes to pruning them -- these plants bloom on new and old wood. You do not have to worry about lost buds due to improper timing of pruning or bud loss due to extremely cold winters (which is what the OP is discussing).


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RE: Do Hydrangeas only bloom on old growth, not new?

Unless you are looking for blue blooms, h. arborescens and h.paniculata hydrangeas are the way to go. Annabelle is an excellent h. aborenscens--white; some popular h. paniculatas are the two-toned pink and white Vanilla Strawberry and Pinky Winky (and others) or the white Limelight (larger) or Little Lime (smaller---but not that small--just 5 ft compared to the 10 ft of Limelight). There are a number of other h. paniculatas also. They bloom during the last half of summer. The h. aborenscens bloom the first half of the summer.

If you live in Zone 6 (or at least in my zone 6), you can count on most of your h. macrophyllas NOT BLOOMING at least 50% of the time. Winters are too cold.

Kate


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