Do Hydrangeas only bloom on old growth, not new?

9 years ago

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....

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Comments (4)

October_Gardens
9 years ago
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).
vasue VA
9 years ago
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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You are basically on the edge of the "northern" and "southern" halves so feel free to experiment. If you fertilize in April & July, make sure that (a) fertilzing in April will not trigger growth that a frost will then kill and (b) fertilizing in July will not delay the start of dormancy in the Fall. You want the plants to start going dormant by or before your average date of first frost. Likewise, you want to fertilize after your average date of last frost in Spring. For example, for Baltimore, the date of last frost in Spring is around April 11 so, you could try fertilizing then or about 1-2 weeks afterwards. The average date of first frost in the Fall is October 29 so fertilize in July and observe if the plant starts going dormant by October 29 or 1-2 weeks earlier. Using organic fertilizers like organic compost, composted manure or cottonseed meal helps with this because they are slow-release fewrtilizers. Chemical fertilizers can also be used but look to see that they claim being "general-purpose" and "slow-release". I would not prune these 20-yr old varieties in Spring because all mopheads, including the rebloomers, always develop their Spring blooms way back in July-August. So pruning before they leaf out in Spring basically cuts off the Spring blooms. With reblooming hydrangeas that is not an issue since they rebloom again later on. But your 20-yr old mopheads are probably not rebloomers. Best time will be to prune any time after they have bloomed in Spring thru and including the end of June.
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Another possibility: If you are fertilizing them: Stop! Just add an application of compost in the fall and spring. If you have a nearby lawn area and you fertilize it, you could be getting runoff and since lawn fertilizer is high in Nitrogen(N), it is promoting lush, green foliage on your Hydrangeas, at the expense of blooms. FWIW, some macrophyllas are just cranky and refuse to bloom! I have an old 'Glory Blue' that is about 25 years old and once it stopped blooming for about 10 years. I had a serious talk with it and promised that it was headed to the compost pile the following year, if I saw no flowers. The following year it produced some huge blooms and has bloomed every succeeding year since then! True story!
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Thanks Randy North of Florida palms has the best deals on Princeps I have seen,that's where I got the 3 I have -one is planted. Seeing them up close might leave you a little more torn between the two. That said,I love Waggies too! Here's the One I have planted- chadec I know exactly what you mean about Aloifolia! Mine snapped(in high winds)2 years ago or it would be 6' right now at least! They root easily so,no worries there-mine is secured to a small post now...probably would have been halved anyway when the "G-house collapsed in the blizzard last winter. Here's a picture(s) of the Cactus cover - Note how tall it is in respect to the railing- and check put what it looked like collapsed under 15"+ of snow! Here is a link that might be useful: Princeps
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Yes, flowers from the fresh growth as you describe is flowering on new wood. Flowering only on old wood was beneficial for types from short growing seasons when the resources and weather were right for reproduction. Think those from areas with deep, cold winters and areas where the rains come during a short season and the rest of the year is either very hot and dry, or cold and dry. Many of these types are also deciduous, they lose their foliage during the coldest (or, in cases such as R. Minutifolia, they go summer dormant and bare) times then rapidly regrow the foliage when the warmer, rainy weather arrives. Most species roses fall in to this group as do Albas, Hybrid Chinas, Gallicas, Damasks, Centifolias, early Mosses. More evergreen types (except things like Banksiaes and Laevigata) have the ability to flower not only on some of that old wood, but also on growth which they have just produced. Many Bourbons, Hybrid Perpetuals, Portlands, later Mosses, Chinas, Teas, most Noisettes, most Hybrid Musks, Hybrid Teas, polyanthas, floribundas, miniatures (most) and many shrubs are either remontant, meaning they will flower in spring, then at some time later in the growing season, or they are more reliably "repeat flowering", meaning they cycle regularly or even continuously during that season. There is bound to be confusion in all of this due to climate and weather. Banksiae flowers when the weather is very "spring-like". When the really hot, dry weather arrives, like almost all once-flowering types, it stops flowering and just grows. Plant it where "spring" lasts for months and it responds by flowering for months, leading some to think they've found a "repeat blooming Banksiae". Nope, as with every other response from every other plant, it is simply responding to the conditions it encounters. Purezza is a Banksiae hybrid which flowers repeatedly...unless you live where it remains cool, then it might not flower at all. The hotter it is, the more Purezza flowers. Shrubs, get ready for a headache. "Shrub" simply means a bush type of growth. Anything which does not generate the overly long "climbing" canes is a shrub. In a harsher climate, quite a few "climbers" grow like "shrubs". In endless summer climates, many shrubs grow like "climbers". Many once flowering types will "repeat" their bloom in cool climates where the spring-like conditions continue for months. What's particularly surprising is many of those which flower on old wood, WILL flower on new shoots they produce in cool weather. Quite a few which require the warmth to flower, won't flower where and when it's too cool. You may be surprised to witness how many "repeat flowering" types which don't repeat because the heat/warmth doesn't last long enough.
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jazzmom516 (Zone 6b, MA)
9 years ago
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).
dublinbay z6 (KS)
9 years ago
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

Do Hydrangeas only bloom on old growth, not new?

Comments (4)

October_Gardens

vasue VA

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jazzmom516 (Zone 6b, MA)

dublinbay z6 (KS)

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