Hydrangeas forum→Help save my hydrangeas!

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MeowCNM
Jul 11, 2018 6:41 PM CST
We planted these hydrangeas this year and recently started noticing the leaves are getting brown and yellow spots on them. We used a fungicide when we first saw the spots but now things are getting worse. We water at least 3 times a week and live in central PA (zone 6B). Please help! Thanks!
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Name: Luis
Hurst, TX, U.S.A. (Zone 8a)
Dog Lover Region: Texas Salvias Roses Hibiscus Plumerias
luis_pr
Jul 12, 2018 12:11 AM CST
Hello, MeowCNM. The shrubs are fine. Just suffering from leaf spot, transplant shock and the Summer Blues.

The leaves have a common fungal disease called cercospora leaf spot. It is promoted by overhead watering. The fungi exists all over so the plants may have caught the infection in the wholesaler's greenhouses, the plant nursery where you bought them or from your own yard. See the link below for more info on cercospora and control fungicides.

http://www.aces.edu/pubs/docs/...

There are no fungicides that cure this problem, only fungicides that help control the leaf spots. So the only "cure" would be to replace an infected plant. The fungicides that are available will control the infestation somewhat but consider if you want to do that at this time of the year... on the one side, the fungicides cost money and on the other side, the infected leaves will be dieing / drying out as Fall arrives... so depending on the severity and the number of shrubs infected, it may or may not be a good investment. You also need to apply the fungicides earlier so I am unsure if using them now will aid with control much this year.

The problem can be brought under considerable control by following good sanitation techniques. Start by watering the soil and never the leaves. If using a sprinkler, water around 6-8am so the leaves remain wet for a little time before the sun comes out and evaporates the water drops. The worst of the leaves can be cut but, since some of these shrubs are now developing invisible flower buds for 2019 in some locations, I suggest that you remove leaves by cutting the petiole string... the string that connects a leaf to the stem as opposed to cutting the stem. The ends of the stems is where these invisible flower buds reside. Do not overwater as this creates a humid environment, which is just what the darn thing needs to grow. Increase air flow between plants by keeping these away from other shrubbery. And definitely, when there is plant debris from infected shrubs, remove the leaves/blooms/dried out branches or stems and throw them into the trash, not in a compost pile. As soon as you notice any fallen leaves from infected plants, pick them up and throw them in the trash. You can also replace the mulch with new mulch.

I have one infected hydrangea that was already that way when I moved into the house. It remains infected but the infestation has been controlled very well withuot fungicides and, in the last 15++ years, it has not spread the disease to other nearby hydrangeas. The leaf spots becomes visible when chlorophyll production starts to taper down in the Summer, although I have seen faint leaf spots earlier sometimes. In years when the end of Summer or start of Fall are rainy, the infestation may be worse than in drier years. I use drip irrigation for all hydrangeas and try to water the soil when hand watering or water around 6-8am.

Some blooms in the pictures look like they are spent and changing colors while others look like they are browning out too early, which suggest a watering issue. All normal for a hydrangea's first year.

Some blooms and some plant leaves look slightly wilted which tells me that the temperatures were 85F of more when the pics were taken. Newly planted shrubs have a limited small root system that was cut to fit into the pots. As a result, the shrubs cannot uptake water via the roots as fast as the leaves loose the moisture. Provided that their soil is kept uniformly moist, they should fix themselves by the morning. There is going to be fungi in the blooms so, when you cut them off, throw them in the trash.

If you want to leave the blooms "on" the shrub (for winter interest), you can do so (just remember to throw them away in the trash at some point). If you want to prematurely remove the blooms now, you can also do so. But, be aware that invisible flower buds for early Spring 2019 are now or soon will be developing near the ends of the stems so, cut the petiole string that connects the bloom to the stem instead of cutting the stem.

Remember in the Summer months to increase the amount of water that the shrubs get. Or increase the frequency of waterings. Or both. When to water: when a finger inserted to a depth of 4" feels dry. This uniformly watering method can help with the wilting/drooping but never completely eliminates it. As things get hot and temps reach 85F or so, you will notice leaves and blooms that end pointing down. A shot of water can immediately fix that but with soils that do not drain well, multiple waterings per day may lead to root rot. So resist the temptation to always water when they are wilted unless you have really well draining soil or sandy soil. Do monitor these shrubs for wilting though, especially in the Summer or in windy days. They will need extra water a lot until they become established.

With temperatures in the 100s or above daily here in Tx, monitoring them is something I now am doing often, almost daily. At around 6-8am, they should be recovered by themselves from wilting if the soil was kept moist. So I check them in the morning and water any that remain wilted in the morning. Or you can test soil then and also water those whose soil feels dry in the morning.

If I see wilting in the Summer, I immediately water 1 gallon of water per plant IF the wilting episode looks extreme. If it is not extreme, I either wait to ck in the morning or I insert a finger into the soil to a depth of 4" and water the soil (1 gallon) if the soil feels dry.

Mulching also aids greatly, conserving the water that you give them... by making the water not evaporate quickly. So keep them well mulched, 2-4" up to the drip line or a little more. Water the soil early in the mornings (6-8am) and do it from the root ball outwards as this is where the roots currently are. You can use any organic mulch but no rocks as mulch.

How much to water varies. You want to get the soil moist down to 8" each time that you water. Watering deeply and less frequently works best but hey, planting a water hungry shrub like hydrangeas in the middle of the Summer requires to skip that step until they are established in the garden and have developed a larger root system (can take from 1-3 years).

In the Spring, I water 1 gallon per plant. As soon as temps go above 85F in May, I water 1.5 gallons per plant. If you get into worse temps, feel free to increase even further or water more often. But do it when the soil feels dry or almost dry so you do not overwater and get root rot. In the Fall, I dial things back to 1 gallon per plant. When the shrubs go dormant, I water once every week or once every two weeks (depends on whether it rains or is dry). If the soil freezes where you live, stop watering when the soil freezes. Resume Spring level waterings when the soil thaws or there is leaf out. Tweak my suggested watering amounts as needed for your own soil and size of plants: water 50% more if your soil is sandy, etc.

Does that help you? Luis
[Last edited by luis_pr - Jul 12, 2018 2:52 AM (+)]
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canada 4b (Zone 8a)
Dirtmechanic
Jun 28, 2021 9:08 AM CST
luis_pr said:Hello, MeowCNM. The shrubs are fine. Just suffering from leaf spot, transplant shock and the Summer Blues.


My wife asked me to look at her hydrangea. It looks like a fungal attack combined with a lack of iron and other nutrients. What say ye, Oracle? I put out some cornmeal and moistened the area and then sprayed a commercial trichoderma preparation that also contained Bs and some other ingredients to purpose. It had a liquid fertilizer called Hasta Grow that is heavier on P and has Iron etc with humic materials. I tested the pH and found it floating between 6.3 and 6.8pH. Zone 8a south of Birmingham AL. Wet summer, 90f temps of late. Site is surrounded by trees in a more naturalized setting and she planted a redbud in the area (6 feet tall now) which I understand loves to attract anthracnose. I say that because this was not a problem over the past decades, and now this.


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[Last edited by Dirtmechanic - Jun 28, 2021 9:27 AM (+)]
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Name: Luis
Hurst, TX, U.S.A. (Zone 8a)
Dog Lover Region: Texas Salvias Roses Hibiscus Plumerias
luis_pr
Jun 28, 2021 11:47 AM CST
Hello, dirtmechanic. I see your oakleaf hydrangea blooms are also turning pink by now too. I noticed that with mine yesterday.

Picture 1: Looks like a case of bacterial leaf spot. That is a fungal infection that primarily affects Hydrangea quercifolia (Oakleaf Hydrangea), Hydrangea arborescens (Smooth hydrangea) and Hydrangea macrophylla (Big Leaf Hydrangea). It starts with individual spots that enlarge around veins. Discard in the trash the worst of the leaves. No signs of iron chlorosis although some foliage is a lighter green color than the older leaves underneath.

Picture 2: more of the same in oakleaf leaves 1 and 2. Severe case of Iron Chlorosis on the macrophylla leaf. The leaves have started turning white-ish. Iron chlorosis works like this: dark green leaves turn light green, except for the leaf veins which remain dark green. Then the leaves turn yellow, except for the leaf veins which remain dark green. Then the leaves turn white, except for the leaf veins which remain dark green. The leaves then die and drop.

Picture 3-4: severe case of iron chlorosis. The spots are Cercospora leaf spot. A couple of places appear to have the start of bacterial leaf spot.

Copper-based fungicides may help control bacterial leaf spot if applied starting in late spring. I am aware that some people also use compost tea spray on infected leaf but I am not seen recommendations in journals. I think the reasoning is that the compost tea spray introduces beneficial bacteria that is good for combating bacterial leaf spot. Removing diseased leaves as soon as they appear helps prevent further spread of the disease but other times that is not practical... meaning, when the plant is covered with infected leaves (they need some green leaves to produce food for the roots after all).

Fungicides containing chlorothalonil and thiophantate-methyl work to control both cercospora leaf spot and anthracnose. I saw a Bonide Spray Bottle at my Lowes that contains chlorothalonil; not sure if it is for sale on all Lowes though. Dilution rates for raw chlorothalonil-containing fungicides range from 1.4 teaspoons to 2 teaspoons per gallon of water but read the product directions as some products are already diluted and ready to be sprayed. For fungicides containing raw thiophanate-methyl, the dilution rates is usually 1 tablespoon per gallon of water. Apply them every 10 to 14 days as needed. For more severe infections, apply at shorter intervals. Follow all directions on the label when using chemical fungicides. Clean sanitation practices and no overhead watering can also help.

Iron chlorosis can be controlled using any one of these amendments per product directions: garden sulfur, iron sulfate, aluminum sulfate or greensand. Regular applications of organic compost can also help keep the soil pH closer to neutral, which hydrangea leaves do not mind. Because the episode is severe, I would use chelated-iron liquid compounds as they help fix the problem slightly faster.

Does that help you? Luis
PS - If your wife is in warm Birmingham, what are you doing in cold Canada? Brrr. Are you anywhere there that is now just finally getting over late frosts? Or are you roasting near Seattle?
[Last edited by luis_pr - Jun 28, 2021 6:47 PM (+)]
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