Trimming/Pruning Endless Summer Bloomstruck Hydrangeas in mid-spring? - Ask Extension
Hello,
I have a number of Endless Summer 'Bloomstruck' Hydrangeas that look like the photo attached, with leaves around the base and up to halfway ...
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Trimming/Pruning Endless Summer Bloomstruck Hydrangeas in mid-spring? #864107
Asked April 11, 2024, 1:02 PM EDT
Hello,
I have a number of Endless Summer 'Bloomstruck' Hydrangeas that look like the photo attached, with leaves around the base and up to halfway up the branches, but each one has bare branches that extend well past the last visible new growth. The brown branches don't appear to have any buds waiting to open. I'm wondering whether I can expect growth to appear later or if I should prune the branches back to just beyond the highest buds/growth. I don't want to cut them back if they're healthy, as my goal is to have large, mature hydrangea shrubs around my house foundation and I've been patiently waiting for three years now, but if the branches aren't going to support new growth, I'd like to remove them and make way for new growth where it will occur.
For additional context, these hydrangeas had the same growth pattern last spring, and I did not prune, thinking growth would continue. Instead, they remained scraggly and in late spring/early summer developed brown spots and holes on the leaves and barely produced any flowers. They looked awful all year long. I'm hoping to position them to thrive this growing season and get to their mature size covered in blooms.
Thanks in advance for your assitance!
Hunter
Prince George's County Maryland
Expert Response
Hello Hunter,
While bigleaf hydrangeas (the species pictured, Hydrangea macrophylla) are notorious for first breaking winter dormancy low on the plant (at ground level and buds low on the stems) before leafing-out higher up on stems, in this case, we agree that the stems pictured appear to be dead and not just still dormant. Given that, you can cut them down now to make more room for the emerging basal growth. (Keeping them likely won't hurt anything, other than being an eyesore, if you wanted to wait a couple more weeks to be more certain no buds will begin growth.)
As to why the stems died back, it's hard to say. Sometimes winter weather is responsible (even if we don't have severe cold, a mild spell followed by a quick chill can be enough, as we've experienced in recent years), and sometimes autumn drought or winter dryness can kill any buds that had developed for the following year. In this case, our winter wasn't that dry, but most of last year's growing season was in drought status for much of Maryland. If you didn't happen to water the shrub periodically, maybe it became stressed enough that some of the buds grown on those stems for this year's blooms or foliage died after forming, or never formed in the first place.
Since this variety is capable of blooming on new growth, even if the old-growth buds were lost during autumn or winter, it should still flower later this summer. Anecdotally, we've heard from some mid-Atlantic nursery growers that hydrangea cultivars capable of reblooming sometimes fail to rebloom well during periods of high heat, but we don't know if this applies to all varieties or just some of them. (There are dozens of reblooming cultivars on the market these days.) High heat doesn't just refer to daytime temperatures; if we don't cool off enough overnight, plants remain heat-stressed, and this phenomenon isn't limited to hydrangeas.
All you can do to support good blooming is to make sure the shrub is watered as needed (feel the soil about six inches deep next to the roots and water well only once it becomes somewhat dry to the touch at that depth) and locate the plant where it receives a bit of direct sun. While bigleaf hydrangea will tolerate full sun, it does stress them and fade any flowers faster, but too much shade can suppress flowering, so a mix of sun and shade is ideal. Fertilizer shouldn't be needed unless a laboratory soil test indicates a particular deficiency (and testing is the only way to be certain), but a mild dose of general-purpose organic fertilizer formulated for acid-loving plants likely won't hurt to try. Since nutrients take time to be absorbed, this will not have an immediate impact on plant health or flowering.
Leaf spot infections are quite common on bigleaf hydrangeas, and we are not aware of any cultivars with significant resistance to those fungi or bacteria. Despite being a bit of an eyesore, they do not threaten long-term plant health and do not need treatment. In fact, using a fungicide would not help much once symptoms manifest, and fungicides are not curative, so will not reverse any existing damage at that point. Fungicides might risk harm to other organisms, though, including pollinators, so we rarely recommend their use overall. Giving plants good air circulation by thinning-out crowded stems and planting them far enough away from a wall or solid fence will help maintain conditions that dry leaves off after rain quickly. Wet leaf surfaces, whether from rain, dew, or irrigation (like a sprinkler), are easier for disease spores to infect, so the longer they stay wet, the higher the risk of infection. Thus, weather from year to year also plays a large role in disease spread and severity.
Leaf holes are also inconsequential, though it's hard for us to diagnose them with certainty without photos. (Feel free to send pictures of symptoms as they appear this year if you'd like help determining the cause.) Very few insect pests chew on hydrangea leaves, and it's more likely that an area of leaf tissue that was infected by a leaf spot disease dried out and crumbled away, leaving a hole; this happens on other plants with different diseases, like cherrylaurel and flowering cherry trees.
Miri
While bigleaf hydrangeas (the species pictured, Hydrangea macrophylla) are notorious for first breaking winter dormancy low on the plant (at ground level and buds low on the stems) before leafing-out higher up on stems, in this case, we agree that the stems pictured appear to be dead and not just still dormant. Given that, you can cut them down now to make more room for the emerging basal growth. (Keeping them likely won't hurt anything, other than being an eyesore, if you wanted to wait a couple more weeks to be more certain no buds will begin growth.)
As to why the stems died back, it's hard to say. Sometimes winter weather is responsible (even if we don't have severe cold, a mild spell followed by a quick chill can be enough, as we've experienced in recent years), and sometimes autumn drought or winter dryness can kill any buds that had developed for the following year. In this case, our winter wasn't that dry, but most of last year's growing season was in drought status for much of Maryland. If you didn't happen to water the shrub periodically, maybe it became stressed enough that some of the buds grown on those stems for this year's blooms or foliage died after forming, or never formed in the first place.
Since this variety is capable of blooming on new growth, even if the old-growth buds were lost during autumn or winter, it should still flower later this summer. Anecdotally, we've heard from some mid-Atlantic nursery growers that hydrangea cultivars capable of reblooming sometimes fail to rebloom well during periods of high heat, but we don't know if this applies to all varieties or just some of them. (There are dozens of reblooming cultivars on the market these days.) High heat doesn't just refer to daytime temperatures; if we don't cool off enough overnight, plants remain heat-stressed, and this phenomenon isn't limited to hydrangeas.
All you can do to support good blooming is to make sure the shrub is watered as needed (feel the soil about six inches deep next to the roots and water well only once it becomes somewhat dry to the touch at that depth) and locate the plant where it receives a bit of direct sun. While bigleaf hydrangea will tolerate full sun, it does stress them and fade any flowers faster, but too much shade can suppress flowering, so a mix of sun and shade is ideal. Fertilizer shouldn't be needed unless a laboratory soil test indicates a particular deficiency (and testing is the only way to be certain), but a mild dose of general-purpose organic fertilizer formulated for acid-loving plants likely won't hurt to try. Since nutrients take time to be absorbed, this will not have an immediate impact on plant health or flowering.
Leaf spot infections are quite common on bigleaf hydrangeas, and we are not aware of any cultivars with significant resistance to those fungi or bacteria. Despite being a bit of an eyesore, they do not threaten long-term plant health and do not need treatment. In fact, using a fungicide would not help much once symptoms manifest, and fungicides are not curative, so will not reverse any existing damage at that point. Fungicides might risk harm to other organisms, though, including pollinators, so we rarely recommend their use overall. Giving plants good air circulation by thinning-out crowded stems and planting them far enough away from a wall or solid fence will help maintain conditions that dry leaves off after rain quickly. Wet leaf surfaces, whether from rain, dew, or irrigation (like a sprinkler), are easier for disease spores to infect, so the longer they stay wet, the higher the risk of infection. Thus, weather from year to year also plays a large role in disease spread and severity.
Leaf holes are also inconsequential, though it's hard for us to diagnose them with certainty without photos. (Feel free to send pictures of symptoms as they appear this year if you'd like help determining the cause.) Very few insect pests chew on hydrangea leaves, and it's more likely that an area of leaf tissue that was infected by a leaf spot disease dried out and crumbled away, leaving a hole; this happens on other plants with different diseases, like cherrylaurel and flowering cherry trees.
Miri
