Horseradish Dying? Common Causes and Solutions

Growing horseradish can be a satisfying and rewarding experience, but in my experience, it can also be challenging, especially if your plant is not thriving. Despite its hardy nature, horseradish can die if it becomes stressed. If like me, you want to know why your horseradish is dying and how to fix it, then read on to find out.

horseradish planted in soil
Digging out horseradish root

Why Is My Horseradish Dying?

There are several reasons why your horseradish plant is dying; the most common of these is too much or too little sunlight, extreme heat, poor soil conditions, incorrect watering, flea beetles, and certain diseases. 

Let’s find out more about the common reasons why your horseradish plant is dying and how to fix it for a delicious harvest of the spicy root vegetable. 

Too Much or Too Little Sunlight 

Horseradish is a hardy perennial plant that is generally considered easy to grow but both too much and too little sunlight can have negative effects on the growth and health of a horseradish plant. Though because horseradish is usually a tough plant, lighting would have to be pretty extreme either way for the plant to become too stressed and begin to die. Nevertheless, sunlight is important and a contributing factor to the overall health of a horseradish plant.

Too Much Sunlight 

Your horseradish plants need at least 6 hours of direct sunlight per day. If they get more, you will notice that the leaves of your horseradish plant will begin to turn yellow or brown because they are burned. Your plant may dry out and be unable to absorb water and nutrients from the soil. Eventually, the stress will kill your horseradish plant.

If you notice any of the above symptoms, you need to act quickly to save your horseradish plant. If your horseradish plant gets too much direct sunlight daily, you need to provide shade. You can cover your plant with a shade cloth once it receives 6 hours of direct sunlight daily. Or you can consider moving it to a shady area of your garden.

Too Little Sunlight 

If your horseradish plant gets less than 6 hours of sunlight per day, you will notice that its growth is stunted and it has yellow leaves. If your horseradish plant does not get enough sun, it will not be able to produce enough energy through photosynthesis. If your plant can not produce enough energy, it will die.

If your plants are not getting enough sunlight, you need to move them to a sunnier spot. When you do this, you must be careful not to damage the roots.

Extreme Heat 

Horseradish is a plant that will thrive in most climates, but environmental stress caused by extreme heat can kill a horseradish plant. This is because it disrupts your plant’s ability to perform essential functions, such as photosynthesis, nutrient uptake, and water absorption. 

Horseradish can grow in temperatures ranging between 45-75 °F (7-24 °C).  And it generally grows best in cooler temperatures, with its optimum range between 60-65 °F (15-18 °C). If your horseradish plant is exposed to temperatures above 75 °F (24 °C) for a prolonged period, like during a heat wave, your horseradish plant will become stressed. 

This was my mistake and I had to start again when the temperature cooled down again.

If your horseradish plant is dying because of heat stress, it will wilt and have scorched leaves. Additionally, your horseradish plant will have dried out, as during a heatwave, it’s difficult for your plant to get the amount of water it needs. 

The Solution to Extreme Heat Stress 

The best thing to do if your horseradish plant is dying due to excessive heat is to adapt your watering schedule, making sure you water your horseradish plant as soon as the soil is dry. To help keep the soil moist you can add a layer of mulch around your horseradish plants. 

The second thing you can do is to cover your plants during the hottest part of the day (from midday onwards) with a shade cloth during really hot days. 

Poor Soil Conditions 

Horseradish plants are generally considered easy to grow and are not high-maintenance plants, which is something I really love about them. But that is not to say the soil conditions your horseradish is planted in are unimportant. If the soil conditions are poor, your easy-to-grow horseradish may begin to die, leaving you wondering what went wrong. 

If your horseradish was planted in soil that is heavy with clay, full of debris and is not well-draining, the roots would not form properly. This will stop it from getting the nutrients it needs from the soil, causing your horseradish plant to die. 

Speaking of nutrients, it will die if your soil doesn’t have the proper levels of nitrogen, phosphorus, and potassium. Your plant will also become stressed if the soil pH level is off. Signs that your horseradish plant is dying due to the soil conditions are that the plant may become weak and stunted, and its leaves will begin to yellow. 

The Solution to Poor Soil Conditions 

First, horseradish prefers well-draining, loose, loamy soil rich in organic matter. You should prepare the soil before planting by working the soil at least 8 to 10 inches (20-25 cm) deep and removing all debris and old roots.

Second, your horseradish plant prefers slightly acidic/ neutral soil with a pH between 6.0 and 7.5. If the pH is not ideal, you can adjust it by adding either sulfur or limestone, depending on which way your pH is leaning. Or, my preferred method, is to amend the soil with homemade compost and aged manure to feed the soil. Over time, these will increase soil fertility and provide everything the plant needs to thrive.

Third, if you think your horseradish is dying due to a lack of nutrients in the soil, you should add a fertilizer with an NPK ratio of 10-10-10. And you can fertilize your horseradish plants a few times during the growing season thereafter. You can also check the nutrient content of your soil with a home test kit like this one.

Incorrect Watering 

horseradish green leaves closeup

Incorrect watering is the most common cause of dying horseradish plants. These hardy perennials will die if they receive too much water or too little, as both stress the plant. 

Generally speaking, horseradish plants need to be watered once a week. However, if you have experienced lots of rain in a week or are experiencing hotter-than-usual weather, you will need to adjust your watering schedule. 

Overwatering your horseradish plants can lead to waterlogged roots, which can result in a weakened root system, slowed growth, yellowing or wilting leaves, and, eventually, the death of the plant. Overwatering can also create an environment favorable for disease growth, which can further harm the plant. 

Underwatering your horseradish plants can lead to dry, nutrient-deprived soil, which can cause the plant to become stressed and weakened. If your horseradish plant does not get enough water, it won’t be able to extract enough nutrients from the soil to thrive. 

The Solution to Incorrect Watering 

If you think you have watered your horseradish plants too much, simply let the soil dry out before watering again. If you’re not sure when to water your plants, check the soil moisture by testing whether the soil is moist or dry at a depth of about ½ an inch.

If your plant shows signs of overwatering and you are sure you have not overwatered it, it could be that your soil has a drainage problem. You can check to see if soil conditions are the cause of plant death by digging a hole (about 23 inches or 60cm deep) and filling it with water. If the soil drains within 4 hours, you most likely overwatered your plants. However, if the water remains, the problem is that the soil does not drain properly.

If you think you have not watered your plants enough, you can simply adjust your watering schedule.

Flea Beetles 

Flea Beetle
Flea Beetle

Horseradish plants can be susceptible to a range of pests that can cause damage or even kill the plant if left untreated. The most common and destructive pests that like to munch on your horseradish plants are flea beetles. 

Flea beetles are small, black, or brown beetles that can cause extensive damage to the plant, eventually resulting in its death. These beetles overwinter in the soil in your vegetable garden or plant debris. Flea beetles jump when disturbed and leave your plant leaves with a ‘shothole’ appearance. 

If your horseradish plant has a flea beetle problem, my favorite solution is to apply neem oil to your plant. Another option is to spread diatomaceous earth around your plants to stop the flea beetles from hopping onto your plants.

Applying a layer of much around your horseradish plants can also prevent flea beetles that have overwintered in the soil from reaching your plants. 


planted horseradish's green leaves
Horseradish plant leaves

Several diseases could be the cause of your dying horseradish plant. Not all diseases will kill your horseradish plant, but diseases such as root rot and brittle root are catastrophic. 

Root Rot 

Root rot is a fungal disease that can affect the roots of horseradish plants, leading to their decay and ultimately causing the plant to die. This disease is caused by waterlogged soil. If your plant is suffering from root rot, it will begin to wilt, and its leaves will turn yellow. 

Sadly, it is very difficult to revive a horseradish plant that is suffering from root rot. You can remove the infected portions of the plant, but it is not always successful in fixing the problem. 

Brittle Root 

Brittle root is a bacterial infection and one of the most destructive diseases that can affect your horseradish plants. This disease is spread by beet leafhoppers and causes poor growth and chlorotic leaves that eventually wither and collapse.

As the name implies, the roots of the horseradish plant become brittle and discolored. When you break your horseradish root in two, you will notice a dark brown ring inside.

Unfortunately, as with root rot, it cannot be saved once the horseradish plant is infected with brittle roots. The best solution here is prevention. To prevent brittle roots, you must ensure your plants are not infested with beet leafhoppers.
To control the beet-leafhopper population, you should also keep your garden free of weeds and debris. Additionally, you can protect your plants by covering them with floating row covers.

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