Botrytis blight is gray mold. A fungus turns damaged or aging hydrangea flowers, buds and leaves to brown mush under a fuzzy gray coat, mostly in cool, damp, still weather.

The fix is cutting out the sick tissue on a dry day, moving air through the shrub and watering at the soil. Which cuts are safe depends on your hydrangea type and zone.

Botrytis Blight: What You See

NC State Extension Gardener Plant Toolbox lists leaf spot, bacterial wilt and powdery mildew on hydrangeas, plus rust and bud blight on panicle types. The gray mold pattern below is what gardeners call botrytis blight.

• Fuzzy gray or tan mold coating flower heads, especially old blooms packed tight.
• Brown, water-soaked blotches on petals that spread until the whole cluster turns papery.
• Flower buds that brown and never open after a cool, wet spell.
• Brown patches on leaves and soft stem tips that touch dead blooms.
• A puff of gray dust when you brush an infected head on a dry day.

It appears as blooms open and again as they age, and foliage that stays wet overnight is the pattern to watch.

Botrytis Blight or Something Else?

Several hydrangea diseases leave brown marks, so where the damage sits matters more than its color. NC State Extension Gardener Plant Toolbox names leaf spot, powdery mildew and rust among them, with rust listed on panicle types.

Gray mold has a soft, fuzzy coat that puffs dust, and it favors flowers and buds. Run a dry finger over the spot and note the color of what comes off.

The full leaf-spot picture is in Cercospora Leaf Spot on Hydrangeas: Signs, Treatment and Prevention. A shrub that wilts while its flowers look fine points to the roots, covered in Armillaria Root Rot on Hydrangeas: Signs, Treatment and Prevention. The rest sit in Hydrangea Diseases.

What Causes Botrytis Blight, and Where It Is Worst

The cause is a fungus that thrives where air is still and plant surfaces stay wet, and NC State Extension Gardener Plant Toolbox gives panicle hydrangea zones 3a to 8b and bigleaf 6a to 11b. The regions below follow climate and type.

• Great Lakes and the North (Michigan, Minnesota, Wisconsin): panicle and smooth types dominate, and cool, damp late-summer weather keeps old blooms wet.
• The South (Georgia, Texas, the Carolinas): humid nights and dense shade planting hold moisture on bigleaf flowers.
• Pacific Northwest (Washington, Oregon): long, wet springs and falls give the mold plenty of time.
• Dry interior West (Arizona, Nevada): low humidity makes gray mold rare unless irrigation wets the blooms.

Your state’s page on this site sets the timing and the type advice for your zone.

How to Treat Botrytis Blight

Start this week, on a dry morning, and work in this order.

1. Remove infected flowers and stem tips: cut just below the gray or brown tissue into healthy green, and bag everything.
2. Cut no deeper on old-wood types: NC State Extension Gardener Plant Toolbox says bigleaf forms buds the previous summer, so hacking back removes next year’s flowers.
3. Clean your pruners between cuts: wipe the blades so you do not carry spores from one stem to the next.
4. Rake fallen petals and leaves: mold overwinters on debris, and it belongs in the trash, not the compost pile.
5. Water at the base, in the morning: leaves and blooms should be dry well before evening.
6. Ask your state extension service about fungicides: only it knows what is registered for hydrangeas where you live.

Panicle hydrangeas bloom on the current season’s growth, so they tolerate harder cutting than bigleaf. Confirm your type before you pick up the shears.

How to Prevent Botrytis Blight Coming Back

NC State Extension Gardener Plant Toolbox notes that bigleaf and panicle are both shallow-rooted and benefit from mulch, which is the first job of the year.

• Early spring: lay mulch over the roots so rain does not splash spores from the soil onto low leaves.
• Late winter, panicle and smooth types: cut back hard, since they flower on new wood, and open the center for air.
• Bloom season: water at the soil line in the morning, never over the flowers.
• Midsummer: pull weeds and thin crowded neighbors so air moves around the shrub.
• After bloom and in fall: remove spent, moldy heads and clear the ground beneath.
• After leaf drop: cut hollow stems to 12 to 24 inches, and leave healthy ones standing for nesting bees.

Bag any stem that carried mold, however tall you leave the rest.

Where this comes from

NC State Extension Gardener Plant Toolbox lists bud blight on panicle hydrangea.

Before you spray anything, check with your state’s extension service. It can confirm the diagnosis and tell you what is approved in your state.

Common questions

Will botrytis blight kill my hydrangea?

It mostly ruins flowers, buds and soft new growth rather than the woody shrub. If the whole plant wilts while the blooms look fine, look at the roots instead.

Can I cut off blighted flowers on a bigleaf hydrangea?

Yes, but take only the infected head and a little stem. Bigleaf sets next year’s buds on old wood, so deep cuts cost you blooms.

Does my hydrangea type change the plan?

It does. Panicle flowers on new growth and takes hard late-winter cutting, while bigleaf, oakleaf, mountain and climbing types flower on old wood. Cleanup and airflow apply to all of them.

Sources : gerbeaud.com

The practical answer is to confirm it, remove the plant and protect its neighbors. Your zone and the type of hydrangea you grow decide what goes back in that spot.

Bacterial Wilt: What You See

The NC State Extension Gardener Plant Toolbox names bacterial wilt among hydrangea diseases, and what you notice first is a shrub that cannot keep its leaves supplied with water.

• Leaves droop and hang limp, often on a few shoots before the whole shrub follows.
• The wilting stays put after a deep watering, where plain thirst is gone by morning.
• Leaves turn brown and dry at the edges, then across the blade, and cling to the stem.
• Flower heads sag and dry out well before their season is over.
• A cut stem shows dark or brown streaking inside the wood where it should look pale.

Bigleaf and panicle hydrangeas are both shallow-rooted, so a dry spell can imitate every sign above. That is why the test is whether the leaves stay limp after a deep watering, not how they look at 3 p.m.

Bacterial Wilt or Something Else?

Three problems get mistaken for this one more often than the real thing. The NC State Extension Gardener Plant Toolbox lists leaf spot and powdery mildew right next to bacterial wilt, and thirst needs no source at all.

Each has one sign that settles the question. You can check all three in a single slow walk around the shrub, with a finger for the soil and a look at the underside of a few leaves.

Leaf spot has a full sheet at Leaf Spot on Hydrangeas: Signs, Treatment and Prevention, and flower-head problems are covered in Botrytis Blight on Hydrangeas: Signs, Treatment and Prevention. The other kinds are on their own pages under Hydrangea Diseases.

What Causes Bacterial Wilt, and Where It Is Worst

Bacteria cause it. They move inside the plant’s water-carrying tissue and travel on dirty pruners, in splashing water and on cuttings taken from an infected plant.

The NC State Extension Gardener Plant Toolbox lists the genus at USDA zones 3a through 9b. What changes from region to region is the type of hydrangea at stake.

• Great Lakes and the North (Michigan, Minnesota, Wisconsin): panicle, rated 3a to 8b, and smooth, the hardiest of the genus, are the shrubs most yards carry, so a loss here means replacing one hardy type with another.
• The South (Georgia, Texas, the Carolinas): bigleaf, rated 6a to 11b, is at home here beside panicle and oakleaf, and its shallow roots dry out fast in summer heat, which muddies the diagnosis.
• Northeast and Mid-Atlantic (New York, Pennsylvania, Virginia): bigleaf and panicle share the borders, and each needs its own replacement plan because bigleaf blooms on last year’s wood and panicle on the current season’s growth.

Your state’s page holds the zone verdict and the calendar that this national sheet cannot give.

How to Treat Bacterial Wilt

Work through these steps in order this week, before you decide anything about replacing the plant.

1. Run the watering test: soak the root zone deeply in the evening and look again at first light, because a thirsty shrub recovers and one with bacterial wilt does not.
2. Cut one wilted stem and look inside: use clean pruners and note any brown or dark streaking in the wood.
3. Call your state extension office: it can confirm the diagnosis, and it alone knows what is registered for use in your state.
4. Stop taking cuttings or layering from it: propagation by stem cutting or layering carries the problem straight into the new plant.
5. Remove the whole plant, roots included: bag it for the trash and keep it out of the compost pile.
6. Disinfect your tools and wash your boots: soil and sap on blades are how it reaches the next shrub, so follow your extension office’s advice on how to clean them.

I would hold off replanting in the same hole until extension says it is fine. When you do replant, match the type to your zone, since panicle and bigleaf differ by several zones.

How to Prevent Bacterial Wilt Coming Back

Prevention is mostly housekeeping, and it follows the shrub’s year.

• Late winter: clean your pruners before cutting panicle or smooth hydrangeas, which bloom on the current season’s growth and take hard cutting back.
• Planting time: buy healthy stock and reject any plant with dark streaks in the stems or limp leaves in the pot.
• Spring: spread mulch over the shallow roots, and keep it pulled back from the stems.
• Summer: water at the base in the morning so leaves stay dry, and never work among wet shrubs with pruners.
• Autumn: rake up fallen leaves, and if you leave hollow stems standing for native bees, the NC State Extension Gardener Plant Toolbox says to cut them back to 12 to 24 inches.
• Whenever you propagate: take cuttings or layers only from shrubs that have never wilted.

Clean tools do more than any product I can think of, and they cost nothing.

Where this comes from

The disease names, zone ranges and habits come from the NC State Extension Gardener Plant Toolbox entry for Hydrangea.

Take a wilted stem or a photo to your state’s extension office before you dig anything up. They can confirm the diagnosis and tell you what applies in your zone.

Common questions

Can a hydrangea recover from bacterial wilt?

I would not count on it. A shrub that stays limp after a deep watering should be treated as infected until extension says otherwise, and the safe move is to remove it before it spreads.

Can I compost the infected plant?

I would not. Bag the plant, roots included, and put it in the trash so nothing carries the problem to healthy beds.

Which hydrangea should I plant instead?

That depends on your zone and how you want it to bloom. Panicle is rated 3a to 8b and bigleaf 6a to 11b, so check your state’s page for the type that fits, and see Hydrangea Diseases for the other problems to watch.

Armillaria root rot is a soil fungus that rots the roots and the bark at the base of a hydrangea, and once it has girdled the crown, no spray brings the shrub back. What you can do is confirm it, remove the plant, and change what goes in that spot.

Armillaria Root Rot: What You See

The disease works underground first, so the above-ground signs look like a thirsty plant that never recovers after watering.

• Leaves yellow, droop or stay small on part of the shrub or all of it, often in summer heat while the soil is moist.
• Stems die back branch by branch, and flowering thins out or stops.
• Under the bark at the base, a white to cream fungal sheet spreads in a fan shape.
• Black strands like bootlaces cling to roots or run through the soil near the crown.
• Clusters of honey-colored mushrooms appear at the base in fall, usually after rain.
• Bark on the lowest part of the stems turns soft, cracked or loose.

One sign alone proves little, but the white sheet under the bark is the one that decides.

Armillaria Root Rot or Something Else?

Wilting and dieback have many causes, and most of them are easier to fix. The NC State Extension Gardener Plant Toolbox names bacterial wilt among hydrangea diseases and calls nematodes rarely a problem.

Frost is the third suspect, especially on bigleaf. Its buds form the previous summer on last year’s wood, so a late frost or a spring prune removes the flowers without touching the roots.

Spots and pustules on leaves point elsewhere, and those problems have their own pages: Hydrangea Rust on Hydrangeas: Signs, Treatment and Prevention and Anthracnose on Hydrangeas: Signs, Treatment and Prevention. The full list sits in Hydrangea Diseases.

What Causes Armillaria Root Rot, and Where It Is Worst

The cause is the Armillaria fungus, which lives on dead roots and old stumps, then reaches living roots of stressed plants through the soil. It follows woodland history and wet ground more than a climate map, so the regions below are about which hydrangeas grow there.

• Great Lakes and the North (Michigan, Minnesota, Wisconsin): panicle is rated 3a to 8b by the NC State Extension Gardener Plant Toolbox and smooth is the hardiest, so lots cleared from woods with stumps left behind carry the risk.
• The South (Georgia, Texas, the Carolinas): bigleaf reaches zones 6a to 11b and oakleaf does well too, and warm, wet soil around old hardwood stumps suits the fungus.
• Northeast and Mid-Atlantic (New York, Pennsylvania, Virginia): every type is grown here, so watch beds built where a tree came down.
• The West Coast (Washington, Oregon, California): irrigated shade beds for bigleaf stay damp at the crown for long stretches.

Your state’s page gives the zone, the type and the calendar that fit your yard.

How to Treat Armillaria Root Rot

Treatment here means confirming the problem and removing the source, done this week in this order.

1. Scrape the bark at the base: use a thumbnail or a knife at the soil line, and a white sheet under the bark settles the question.
2. Call your county extension office: send a photo or a sample, because the state extension service alone knows what is registered where you live.
3. Pull mulch off the crown: hydrangeas are shallow-rooted and like mulch, but keep it a hand’s width from the stems so the bark can dry.
4. Dig out the dead shrub with as many roots as you can: root pieces left in the ground keep the fungus fed.
5. Remove nearby stumps and large roots: an old stump within reach of the bed is the likely source.
6. Leave the hole without a hydrangea: ask the extension office which plants tolerate the spot before you replant.

I name no fungicide because I cannot see your state’s registered list. A shrub with a few dead stems and a sound crown may hold on, but watch it through the next fall.

How to Prevent Armillaria Root Rot Coming Back

The NC State Extension Gardener Plant Toolbox lists hydrangea maintenance as low and asks for good drainage, with occasional wet soil acceptable, so prevention follows the calendar.

• Dormancy: the one safe window to move a plant, roots undisturbed, and the time to clear old stumps from the bed.
• Planting: choose a spot with good drainage and set the crown at soil level, never buried.
• Spring: refresh mulch over the shallow roots and keep it off the stems as growth starts.
• Summer: water at the soil line in dry spells, and keep mowers and string trimmers away from the bark at the base.
• Fall: check the base after rain for honey-colored mushrooms and scrape one stem if the shrub looks tired.
• Every year: match the type to your zone, since a stressed plant is the one the fungus picks.

Pruning dates and hardiness differ by type and by state, so use the page for your state before you cut anything.

Where this comes from

The hydrangea types, zones and drainage notes here come from the NC State Extension Gardener Plant Toolbox, Hydrangea entry. That source names leaf spot, bacterial wilt and powdery mildew, plus rust and bud blight on panicle, but does not list armillaria.

The descriptions of the fungus are general, so confirm any diagnosis with your state’s extension service. They can tell you what is present locally and what is allowed in your state.

Common questions

Can a hydrangea recover from armillaria root rot?

Once the white sheet has spread around the crown, recovery is unlikely. A shrub with a sound crown and a few dead stems may hold on, so confirm with your extension office before you dig.

Does it hit every type of hydrangea?

Any type can be hit, so the difference is in the replacement you choose. Bigleaf is rated 6a to 11b and panicle 3a to 8b, so type and zone decide what goes back in.

Do mushrooms at the base mean the shrub is doomed?

Honey-colored mushrooms mean the fungus is active in the wood nearby, and it may be feeding on a stump instead. Scrape the bark at the base and look for the white sheet before you decide.

Sources : tnstate.edu | plantpathology.mgcafe.uky.edu

Anthracnose on a hydrangea is a fungal leaf disease. It shows up as tan to brown spots that spread in warm, wet weather, and it usually marks the plant rather than kills it. The fix is mostly housekeeping: dry leaves, cleaned-up debris, and no hard pruning on the wrong type. Here is what to look for, inside our Hydrangea Diseases guide.

Anthracnose: What You See

The NC State Extension Gardener Plant Toolbox lists leaf spot among hydrangea diseases and gives anthracnose no entry of its own, so these signs follow the general leaf-spot pattern. Look for:

• Tan, brown or gray-brown spots on the leaves, often ringed darker.
• Spots that run together into large dead blotches.
• Browning that starts on lower, shaded leaves and climbs.
• Dead patches along leaf edges after a long wet spell.
• Worst from late spring through summer, whenever leaves stay wet for days.

Spots that sit sunk into the leaf and don’t wipe off are the fungus at work. Old spots never turn green again, so judge progress by the new leaves.

Anthracnose or Something Else?

Several hydrangea problems brown a leaf. Color alone won’t sort them, so look at texture and pattern instead.

The NC State Extension Gardener Plant Toolbox says bigleaf needs protection from afternoon sun. That is the first cause to rule out when the browning sits on one side of the shrub only.

Bacterial wilt is also named by that source, and it shows as whole shoots going limp, not spotted leaves. Mildew has its own sheet: Powdery Mildew on Hydrangeas: Signs, Treatment and Prevention. Whole-plant decline is a different story, covered in Armillaria Root Rot on Hydrangeas: Signs, Treatment and Prevention.

What Causes Anthracnose, and Where It Is Worst

A fungus causes it. It overwinters in fallen leaves and plant debris, then splashes onto new growth whenever foliage stays wet.

The NC State Extension Gardener Plant Toolbox puts panicle at 3a to 8b and bigleaf at 6a to 11b. It offers no map of disease pressure, so the regions below follow leaf wetness, not a published ranking.

• Great Lakes and the North (Michigan, Minnesota, Wisconsin): panicle and smooth types dominate, and humid summer stretches with heavy dew keep leaves wet.
• The South (Georgia, Texas, the Carolinas): bigleaf grows here, and long warm, humid seasons give the fungus more weeks to spread.
• Pacific Northwest (Washington, Oregon): wet springs and mild temperatures keep foliage damp for long periods.
• Dry interior West (Colorado, Utah, Nevada): lower risk, unless overhead sprinklers keep wetting the leaves.

Your state’s page has the local calendar for pruning, mulching and cleanup, matched to your zone and hydrangea type.

How to Treat Anthracnose

Start this week, in this order. Most of it costs nothing and does more than any bottle.

1. Remove spotted leaves: pick them off on a dry day and bag them, never drop them at the base of the plant.
2. Rake the ground clean: fallen leaves carry the fungus, so clear everything from the soil under the shrub.
3. Water at the soil line: use a hose or drip line in the morning, and keep sprinklers off the foliage.
4. Hold the pruners: the NC State Extension Gardener Plant Toolbox says bigleaf flowers on last year’s wood, so a spring cut to chase spots removes the buds. Panicle blooms on current growth and tolerates hard cutting in late winter.
5. Give it room: pull back groundcover and neighboring plants that crowd the stems and hold moisture in.
6. Ask your state extension office: it alone knows which fungicides, if any, are registered where you live, and labels differ by state.

Hold off on anything in a bottle until the first five are done. Clean new leaves are the sign it worked.

How to Prevent Anthracnose Coming Back

Prevention follows the calendar, and each step keeps leaves dry or removes the fungus’s winter shelter.

• Late winter: the NC State Extension Gardener Plant Toolbox says panicle blooms on the current season’s growth, so cut it back hard now, but leave bigleaf alone.
• Early spring: refresh the mulch, since bigleaf and panicle are both shallow-rooted and benefit from it, and it also blocks soil splash.
• Through the growing season: water at the base in the morning so leaves dry before evening.
• Midsummer: pick off the first spotted leaves the day you see them.
• Autumn leaf drop: rake and bag every fallen leaf under the shrub.
• Winter tidy: leave hollow stems standing at 12 to 24 inches, because native bees nest in them.

That last step costs nothing in disease control, since the leaf litter is what matters.

Where this comes from

Bloom wood, hardiness, mulch and bee-stem advice come from the NC State Extension Gardener Plant Toolbox entry for Hydrangea. That entry does not describe anthracnose itself, so the disease details here reflect general leaf-spot practice.

Before you spray or prune, check with your state’s cooperative extension service. Registered products and timing vary by state, zone and hydrangea type.

Common questions

Will anthracnose kill my hydrangea?

On an established shrub it mostly disfigures leaves. Repeated bad seasons can weaken a plant, so sanitation matters. Sudden wilting of whole shoots points to a different problem.

Can I compost the spotted leaves?

Bagging them is safer. Home piles often stay too cool to kill the fungus, and the leaves come back to the bed with the compost. Check your local yard-waste rules.

Does my hydrangea type change what I do?

Yes, for pruning. Bigleaf sets buds on last year’s wood, so spring cutting costs flowers. Panicle blooms on new growth and can be cut back hard in late winter. Cleanup and watering are the same for both.

Sources : apps.extension.umn.edu | gardenerspath.com | union.ces.ncsu.edu