How To Fix Hydrangea Root Rot (And Preventive Measures)


Potted indoor hydrangea showing root rot symptom

Who doesn’t love a Hydrangea, with its playful pom-pom flowers? Unfortunately, this jolly plant can be less than joyful if it is overrun by root rot! 

If your hydrangea has started to look under the weather recently, you may be dealing with this fungal infection. 

The good news is Hydrangeas can recover from root rot – but you need to get your skates on! Taking immediate action is the best form of attack when it comes to root rot. 

To fix hydrangea root rot start with trimming off brown, mushy, rotten roots. Use an effective fungicide to disinfect the remaining healthy roots. Then repot with fresh soil mix into a new container.

The longer you leave it, the more likely it is that the rot will take over your plant for good. So let’s avoid that at all costs! Keep reading to find out how to keep that nasty rot away!

Signs of Hydrangea Root Rot

There are several types of Hydrangea root rot which cause different symptoms. 

However, the most common signs of root rot are the following: wilting, yellowing leaves, leaves turning brown, slow but noticeable deterioration of branches, brown roots, and browning of the stem just above the soil. 

Causes of Hydrangea Root Rot

Causes of Root RotWhy This Causes Root Rot
OverwateringOverwatering causes root rot because the roots can’t dry out. This makes them susceptible to fungal spores which cause rot. When there is excessive water present, it can’t drain easily or evaporate quickly. As a result, the soil stays damp, and the roots become susceptible to rot.
Poor DrainageNot all pots are created equal! Some have more drainage holes than others, or raised bases, which encourage water to drain. If water doesn’t drain well, it will end up sitting, trapped, at the base of the pot. Soil which is too damp and can’t dry will result in root rot.
Soil with Poor DrainageSoil may drain better, or worse, depending on what it comprises of. Some soils are too dense to let water and air pass through. Therefore, soil with poor drainage will retain water unnecessarily, keeping your Hydrangea’s roots sitting in moisture. Ultimately, this leads to rot.
Pathogenic InfectionRoot rot is caused by a fungus which can be found in soil or on the surface of a plant. It may enter via the roots or the stem.Once this pathogenic infection starts attacking your plant, it will spread in the roots and cause them to rot.
Extra-Large PotToo large a pot could cause rot for several reasons: It is easy to overwater a plant in too large a pot because there is more soil to keep moist. This can result in supplying more water than your Hydrangea needs.The large area of topsoil may appear to be dry, making you think your plant needs watering, whilst the rest of the soil is still damp. Excessive moisture leads to root rot.
Low TemperatureLow temperatures cause root rot because cool conditions do not encourage moisture evaporation. When temperatures are cooler, the moisture stays in the soil longer. This leads to root rot because the roots are exposed to damp conditions for a long time.
Watering During Dormant PeriodIf you water your Hydrangea during its dormant period, usually in winter, it can lead to root rot. Hydrangeas aren’t growing during this time, so their demand for water is minimal. This means they’re easy to overwater. The water will simply sit in the pot, causing rot, because it will not be absorbed.
Excess Fertilizer ApplicationExcessive fertilizer causes roots to shrivel. This happens because there is salt in fertilizer which can make roots dry out if too much is used. Due to their shrunken and weakened state, roots which have been exposed to too much fertilizer are more vulnerable to root rot. 

How to Save Hydrangea from Root Rot

Here are the actions that you can take to save your root rot affected hydrangea:

Repotting 

Repotting is the number 1 way to get your Hydrangea away from the harmful grasp of root rot. The fungus that causes root rot can be in the soil, on the pot, and on the plant and roots. Repot carefully by following these steps:

  1. Sterilize the new pot before transplanting, make sure to clean it thoroughly along with any tools you may use.
  2. Remove your Hydrangea from its original pot and prune brown, mushy roots (these are infected with rot).
  3. Rinse the root ball of the plant thoroughly to wash off any remaining fungal spores.
  4. Repot using clean, new soil. Re-using soil will risk transferring spores to the new pot.

Using Appropriate Soil Mix

Choosing a soil mix which drains well is an important step against root rot. Remember – don’t use any kind of soil or potting mix which has been in contact with infected plants!

  1. Avoid using soil which has too much clay. This won’t allow enough oxygen to get to the roots, or water to flow past them, and is a cause of root rot.
  2. The best option is to buy potting soil. When selecting a potting mix, choose one that describes itself as ‘well-draining’, that way you’ll be left in no doubt as to the property of the soil.
  3. If you choose to make your own potting mix, include perlite, plant mulch, composted wood chips, and blood meal to ensure the soil is sufficiently aerated whilst giving the appropriate nutrients to your Hydrangea.

Watering After Repotting

There are different rules when it comes to watering your newly re-potted Hydrangea, depending on whether it is dormant or not. 

You need to water a dormant Hydrangea deeply once after repotting. This means you should make sure to damp the soil from the watering.

After this, it may not require much water at all until the dormant period is over.

If you transplant your Hydrangea when it isn’t dormant, you should water it 3 times a week.

Make sure not to water the leaves, and water deeply each time. You must ensure proper drainage to avoid waterlogging.

Care After Repotting

Keep an eye on your newly repotted Hydrangea and make sure it is receiving the right amount of water. 

Whilst Hydrangeas like to be deeply watered, the soil shouldn’t be wet, and you should check that the water is draining well in its new pot.

Paying extra attention to your Hydrangea after repotting is a great way to make sure it doesn’t suffer from the same problems as it did previously. 

Repotting can put a stop to root rot, as long as the pot’s conditions don’t encourage more rot.

Chemical Treatment

You can use fungicide to treat some types of root rot in Hydrangeas.

The fungicide should contain either fosetyl-AI, propaocarb, or thiophanate-methyl + etridiazole.

Spray the fungicide over the plant, following the instructions, before repotting your Hydrangea into new soil.

Homemade Treatment for Hydrangea Root Rot

Now you know how you can treat your hydrangea with root rot. Now, let’s know about some preventive measures so that you don’t have to worry about the risk of root rot infection. 

1. Sterilize the Cuttings

If you take cuttings from your Hydrangea you should use sterilized pruning tools to avoid the spread of any fungal spores transferring from the tools to the plant. 

Spray the cuttings with a treatment of 10:1 water/bleach and gently rub down with a soft cloth or brush before leaving to airdry. 

This should help kill any remnants of spores on the cuttings which would lead to root rot in your new plant. 

2. Seed Treatment Before Sowing

You can treat your Hydrangea seeds with a fungicide before sowing them. This will inhibit seed and soil-borne fungal diseases transferring to the plant when it grows.

Spectracide, Garden Safe Brand Fungicide3, and Bonide are fungicides available on Amazon that you can ally via a light dusting to seeds before planting. 

3. Disinfect Pots

Disinfecting pots before planting your Hydrangeas in them is a great way to control root rot.

Root rot fungus can be present on containers that have come into contact with spores. These spores may have been in the soil, on the plant, or have found their way to the pot by another means.

The best way to disinfect a plant pot is to soak it in a solution of 1-part bleach to 9-parts water for 10 minutes. 

After soaking the pot in the bleach solution, you should take care to wash it thoroughly in dish soap and water to remove the bleach. 

4. Sterilize Soil

Sterilizing soil can kill pathogens in the soil. 

You can sterilize infected soil by placing a layer of soil, about 4 inches (10cm) deep, in a tray/dish suitable for oven cooking.

Cover the soil with foil and bake in the oven for a minimum of 30 minutes at 180-200ºF (82-93ºC). 

You can also sterilize soil using the microwave. Place the soil in a microwavable container and cover with a lid with ventilation holes. For every 1 pound of soil (450g) heat for 90 seconds on full power.

5. Disinfect Tools

The fungi that cause root rot can transfer to other plants by the tools you use. 

You should take care to disinfect all tools that you use on your plants regularly, even if you are not aware of having any plants with root rot.

The last thing your Hydrangea needs is to be attacked by fungal spores which have been transferred from another plant without your knowledge!

Soak tools in a solution of 1-part bleach to 9-parts water after using them, and then wash them with dish soap.

6. Wash Hands Before Handling Plants

It can be easy to go between plants, touching them and pruning them, and not even think about the possibility of spreading something via your hands to one of your plants.

You should try to wash your hands after touching your plants, before tending to the next one. This is a simple way to avoid spreading infections, diseases, insects or spores from one plant to another.

Similarly, your hands may have picked up something harmful from the outside world, which you then bring into your house to your plants, so it’s always a safe idea to wash them regularly! 

7. Maintain Humidity and Temperature

Hydrangeas like humidity and you should keep in relatively warm temperatures, 65-75ºF (18-24ºC).

Maintaining good humidity levels will mean that you aren’t tempted to water your Hydrangea more than necessary, as it will be getting moisture from the air.

Similarly, ensuring that your Hydrangea is kept within its ideal temperature range will help water evaporate when it needs to.

Both of these factors will stop water from stagnating in your Hydrangeas pot, suffocating the roots and causing root rot.

8. Avoid Waterlogging

Waterlogging a Hydrangea is a very common cause of root rot.

The fungus which causes root rot loves warm and damp conditions, which are exactly what waterlogging the soil results in.

Soil gets waterlogged if it doesn’t drain well, if the water isn’t evaporating, or if you simply overwatered your plant!

Make sure to only water your Hydrangea when the top inch (2.5cm) of soil is dry, and check the pot drains well, to avoid enticing root rot!

9. Develop Watering Schedule

A watering schedule is a reliable way to make sure you’re not overwatering (or underwatering!) your plant.

Hydrangeas often naturally wilt in the afternoon heat, and it can be tempting to reach for the watering-can the second you see this happening. 

But wait! Actually, this behaviour doesn’t signal that your Hydrangea needs watering, and you may risk overwatering if you succumb to the temptation!

The best thing to do is develop a watering schedule and stick to it. Start by watering your Hydrangea 3 times a week, always on the same days.

If the top inch (2.5cm) of soil has not dried out, leave longer between watering.

This is a great way to be consistent and make sure the soil has a chance to dry out between watering, thus avoiding root rot!

10. Loosen Soil

Gently loosening the soil can improve drainage. It can also help aerate the soil.

Both of these factors reduce the likelihood of root rot developing. Loosening the soil will allow the roots a chance to breathe and dry out, whilst better drainage avoids excess moisture surrounding the roots.

11. Avoid Overfertilization 

Hydrangeas do not require a lot of fertilization. In fact, they are usually happy with only being fertilized once a year.

Using too much fertilizer can lead to a build-up of minerals. This, in turn, can provoke the growth of pathogenic microflora which cause root rot. 

12. Ensure Care Requirements

Following good care practises will reduce the likelihood of your Hydrangea getting root rot.

Hydrangeas like bright, indirect sunlight and temperatures between 65-75 ºF (18-24 ºC). This will encourage correct water evaporation and make sure the roots don’t get too cold.

Similarly, watering regularly on a consistent schedule will avoid water logging the soil.

During your Hydrangeas dormant stage (normally winter), you will not need to water it as much.

Following these steps will make sure that you keep your Hydrangea in the right conditions to avoid encouraging root rot.

Frequently Asked Questions

  1. How do you revive a dying Hydrangea? 

If your Hydrangea is completely brown and dry, look for new leaf buds on the stems and prune off the dead stems above.

Gently remove all the dead leaves. Check if your Hydrangea is root bound. If it is, repot in a larger container. Water deeply three times a week.

  1. Can you reuse soil that has root rot? 

After a plant has suffered from root rot, the soil it was in will contain fungal spores. You should never reuse the soil.

The fungal spores cause root rot, and any plant that comes into contact with this soil will be prone to infection. This soil needs to be discarded.

  1. How do you revive wilted Hydrangeas? 

Underwatering, overwatering, or too much heat can cause wilting. Water your Hydrangea when the top inch of soil is dry.

Provide bright, indirect sunlight for your Hydrangea and keep it at a temperature of between 65-75 ºF (18-24 ºC). Blooms wilt naturally after 8 weeks and should be pruned.

Arifur Rahman

I'm the owner of gardenforindoor.com. After completing my bachelor of science in agriculture, I'm serving as a civil service officer at the Department of Agricultural Extension, Bangladesh. I started Garden For Indoor to make your indoor gardening journey easy and enjoyable.

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