Hydrangea help

Question: I have hydrangeas in my backyard.  They have appeared to be diseased since we moved in two years ago and I am just getting around to having the time and dedication to clean up this situation.  I would like to know if I can save these plants or if I am better off digging them up and replacing with new hydrangeas.

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied October 07, 2024, 10:22 AM EDT
response: The symptoms look quite typical for end-of-season hydrangea foliage; they can be susceptible to various leaf spot diseases (mostly fungal, some bacterial). Many trees, shrubs, and perennial develop leaf spot issues in summer or autumn. Since the leaves are about to shed for winter in the coming weeks, no intervention is needed, nor would use of a fungicide at this point provide any benefit. Once the leaves have shed on the hydrangeas, you can rake them up and dispose of them (don't compost) to reduce the risk of re-infection next year, as the dead foliage can harbor spores. The old stems that were cut previously are great habitat for stem-nesting bees, and while unrelated to the leaf spot issues, they are great pollinators and may help to control pests on other plants in the garden.  While use of a fungicide next year (starting around mid- to late spring) might help to keep the leaves more free of infection, we generally do not encourage its use since it's a higher-maintenance solution (that won't always work) and it might risk the health of pollinators or other organisms, in part because spraying would overlap with bloom. Maintaining good air circulation around plants by avoiding crowding, plus avoiding wetting the foliage when irrigating during dry spells (leaf surfaces wet for long periods can be easier for spores to infect) can help to reduce the risk of severe infection in future years.  Don't prune stems back in autumn or winter as part of a clean-up, as that can remove most (or all) of next year's flower buds. (They are formed now, and lie dormant on the stems until opening next spring/summer.) If any stems or stem tips remain leafless closer to late spring next year, then you can assume there was some dieback (not unusual) and trim the bare areas off at that time.  Miri

responder: The Question Asker Replied October 07, 2024, 12:25 PM EDT
response: Hi Miri, Thank you for your prompt and informative response.  All helpful information.  I don't have a way to see the photos I attached in my initial inquiry, but part of my concern is also the very dry, hollow stems.  Half of them are hollow, gray and/or brittle to the base of the plant; I don't know if I can save them.  Another concern is that many of the leaves grew in brown, like were never green.  I pruned all the dead leaves and stems Last Fall, or what I could, last year with hopes that that would help for this past Spring and Summer, however they appeared to be diseased upon growing in.  My goal is to have healthy hydrangeas for next year, I would hate for them to grow in brown/unhealthy again.Thanks,NoelleOn Mon, Oct 7, 2024 at 10:22 AM Ask Extension <<personal data hidden>> wrote:

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied October 07, 2024, 3:31 PM EDT
response: The hollow nature of the old, cut stems is normal for hydrangea. They can't be saved because they are already dead (the reason why they were cut, we presumed, though if cut during winter in a prior year, we recommend that not be done again, since it removes flower and leaf buds). Hydrangea that bloom on older growth, as these types do, should only be pruned back that drastically if they need some branches thinned-out (to promote that better airflow through foliage that reduces the risk of disease) or their size needs to be reduced temporarily. While pruning most or all stems during winter will shorten a plant, it will also remove most or all of its flower buds, so any pruning (not for size, but for tweaking shape or density) tends to be done post-bloom instead, which can vary from one variety to another, but generally falls in midsummer.  It's not uncommon for a handful of old stems in a clump of a mature hydrangea to die back during winter and not leaf-out again, even if robust new growth emerges from the roots and the plant looks fine. In that event, once you know those individual stems have died (which will be when they don't have foliage when the rest of the plant does), then they can be trimmed down for aesthetics or to get them out of the way of the new growth. Don't prune too early, since hydrangeas of this type tend to put out new leaves from their base first as the weather warms in late winter or early spring, then leaves emerge from further up the stem; so, wait until the stem tips have leaves before determining which that are still leafless are thus dead and can be cut back.  A reddish-brown tinge to the leaves, even when not infected, can be a sign of stress. Either the plant is exposed to too much direct summer sun (they prosper in a mix of sun and shade), high heat (like near walls or paving reflecting/retaining heat), or not enough soil moisture (not watering during drought, for example). A few cultivars normally have reddened or purplish leaves throughout the season, but they are fairly new to the market and not many gardeners are growing them. A soil nutrient deficiency or acidity level (pH) outside of the preferred range might contribute to unexpected leaf colors; a laboratory soil test can help determine if this is the case, and it will be relatively easy to fix if needed.  Miri