Why Well Water Is Killing Your Plants – And How To Fix It


Domestic wells are generally safe for watering plants. In fact, some minerals common in well water can be nourishing to certain plants in the right amount. Yet groundwater often contains other elements that may generate a level of toxicity and salinity in your well water that could kill your garden.

Well water that contains naturally high levels of sodium, fluoride, iron or nitrogen can cause leaf browning or yellowing, inhibit plant growth and flowering, and eventually the kill the plant. Regular watering from well water that is hard (high in calcium and magnesium) can also result in plants wilting and dying.

This article will explain which elements are commonly found in well water, how they impact your plants and provide solutions for each one. We will also discuss watering alternatives to make sure your garden receives nutrient-rich hydration.

Why is well water killing my plants?

Well water is sourced from groundwater, which usually contains a variety of substances that occur naturally in bedrock.

Since well water is not regulated by the council as opposed to tap water, it is necessary to conduct frequent testing to check that any elements or minerals that are present are within levels that are safe for your plants, pets and yourself.

Well water, especially in shallow wells, may also pick up chemicals and bacteria from the surrounding area, which represents a health hazard to people and vegetation. This is particularly true for low-lying areas, such as Florida.

Even when your well is clean and the mineral levels are within the recommended standards, the reaction of a plant to different elements varies from one species to another. If you have a diverse garden, you might see some plants thriving and others dying

Temperature changes, pets’ urine, pesticides and other factors can also damage the foliage and roots of your plants.

If you notice the following symptoms, there is a high chance that the problem is linked to your water supply: 

  • Leaves quickly turning brown and dying off.
  • No flowering despite applying sufficient fertilizer.
  • Rotting roots even though the soil is not too wet.
  • White powder building up on the soil’s surface.

The next thing you should do is find out what aspect of your water is damaging your plants: mineral levels, pollutants or alkalinity.

That can be done by contracting a reliable laboratory to conduct a test in search of the following elements, and in the meantime you can compare your plants symptoms with each of these possible causes:

1. Sodium

Sodium is a common mineral found in groundwater at low levels. It also appears in soft water because many filtration systems use a process that replaces heavy contaminants with sodium ions.

Other human activities can also increase levels of sodium in well water, such as road salting whose runoff ends up in the neighbouring wells.

Most plants struggle to tolerate sodium. Salt can ruin orchids, bromeliads and other house plants by accumulating around the roots, hindering the absorption of water.

When this happens, regardless of how much you water your plants, they will be dehydrated. Excess salt dries out the plant tissues which stunts their growth and impacts the development of the cells. Salt also builds up in the soil, affecting its structure.

Symptoms:

If you notice your plants wilting and their growth inhibited, they are probably overexposed to sodium.

Solution:

Flushing the soil with fresh water or rainwater is a good way to leach the salt away from the root zone and dilute the effect.

If you have a water softener, you can install a bypass valve to access untreated water to use for your plants.

2. Fluoride

Fluoride is a natural occurring element that can be picked up by groundwater in certain geologies. While most well water contains some level of fluoride, the concentration depends on the nature of the rocks around the well and the presence of any fluoride-bearing minerals.

Plants, particularly the ones with long, narrow foliage, are more susceptible to fluoride toxicity. These include spider plants, palms, oleander and dracaenas.

Yet it is unusual to find natural concentrations of fluoride that are high enough to damage your plants, unless you live in Colorado Springs – which has exceptionally high fluoride concentrations. Tap water is more likely to have added fluoride in some municipalities.

Symptoms:

You can probably blame fluoride when you notice the entire plant withering and the leaves becoming crispy. Brown spots or brown leaf tips are other common symptoms, and there is no recovery for the damaged leaves.

Solution:

Adding calcium in the form of lime (calcium carbonate), which will bond with the fluoride molecules. A general rule of thumb is an application of 1 tablespoon of lime (calcium carbonate) or dolomite per gallon of soil in the immediate area around the plant.

3. Hard water

Hard water is water with high mineral content, mostly calcium and magnesium which come from limestone, chalk or gypsum deposits.

Groundwater often percolates through these deposits, carrying the calcium and magnesium to your private well. In small amounts, these minerals are good for your plants.

Calcium contributes to plant growth and makes plants less susceptible to diseases and pests. Magnesium is a crucial player in the photosynthesis process.

But these minerals can also be harmful, especially for potted plants, because they get trapped in the soil and can cause leaf burn.

When you water your plants with hard water, a substance called limescale, made up of calcium and magnesium, is left behind.

Symptoms:

Limescale produces a white, chalky deposit on the leaves, which makes breathing difficult for the plant. The accumulation of limescale will eventually sicken and wilt your plants.

High levels of calcium can also interfere in the germination of seeds and reduce the growth rate of your plants. Plus it can raise the pH of water, making the soil alkaline which can harm sensitive plants.

Solution:

Wipe down any chalky calcium deposit from your plant’s leaves with a mixture of water and a simple acid solution such as lemon juice or vinegar.

If your leaves turn pale or yellow, consider adding a fertilizer that lowers the pH levels in your soil (makes it more acidic/less alkaline).

4. Nitrogen

Plants need nitrogen for healthy growth and reproduction, and they use it during the process of photosynthesis. While it is essential for plant development, too much nitrogen is also harmful.

Plus the excess nitrates -a byproduct of the plant’s processing of nitrogen- may leach into the groundwater causing nitrate contamination. High nitrogen levels in the water used for edible gardens can make a person sick when eating those vegetables. 

Most nitrogen is naturally present as organic matter in the soil, in levels that are no reason for concern for the health of humans and plants. However, dangerous amounts of nitrogen can percolate easily into the groundwater that seeps into your well from fertilizer runoffs in regions of intensive agriculture. 

Symptoms:

High levels of nitrogen in the soil will cause plants to stop producing flowers or fruit, and their leaves to turn yellow and drop. All plants need nitrogen, but in high amounts it causes burning, which can make the plant shrivel and die.

Solution:

Add some fine woodchips (sawdust will do) to the soil surrounding the plant. The woodchips will help absorb the excess nitrogen. You can also opt to plant some species that thrive off excess nitrogen, such as tomatoes or spinach.

5. Iron

Iron is the most abundant of all metals, and the fourth most common element found in the Earth’s crust by weight. It is introduced into wells by heavy rainfalls and snow melts that seep it from the soil, and it appears in three different forms: ferric, ferrous and bacterial. T

he first is a non-soluble sediment, the second dissolves into groundwater at low oxygen levels, and iron bacteria is a nonpathogenic bacteria. Iron can also enter domestic wells from rusty plumbing.

Water-soluble ferrous iron is the most common version present in water, especially in deep wells. 

Iron plays an important role in respiration, photosynthesis and plant growth, but is only necessary in small amounts. Some plants are inefficient at absorbing iron from the soil, and require low pH levels for iron to be more readily available to the plant roots.

Watering your plants with water that contains ferrous iron will replenish the levels of iron in the soil that was drawn by the plant. Water with ferric iron will have the same effect but at a much lower rate.

But iron is considered a micro-nutrient, only required in trace amounts.

A high amount of iron may pass the natural water-soluble point and start building up around the plant. Long term watering with iron-rich well water can cause toxicity.

Symptoms:

Iron deposits can make plants lose their pigmentation and hamper their production of food or oxygen. They may wilt, turn gray or brown, or even die.

Solution:

The availability of iron to plants can be reduced by adjusting the pH of the soil – low pH increases iron availability, while high pH reduces iron availability. Adding lime (calcium carbonate) to the soil around the plant will increase the pH (make it more alkaline).

Chemical and biological contaminants

In addition to the minerals and metals discussed above, other chemicals may enter your private well and end up absorbed by your plant’s roots. If you live near industrial or intense farming areas, there is a risk of chemical contamination in your well water.

Leakages from old underground storage tanks, septic tanks or lead pipelines can also reach your well through rainwater and snow melt.

Lead, arsenic, mercury, hydrogen sulfide, nitrate and harmful microbes like E.coli can make their way into your well. Some of these contaminants, like lead, mercury and arsenic, are non-biodegradable. Their ability to bioaccumulate makes them highly toxic, inhibiting plant development from cells to roots.

Others like hydrogen sulfide and nitrate, can be stimulating for plants in trace amounts but become toxic at higher levels. In the case of pathogens and bacteria, they are dangerous if the plant watered with these pollutants is consumed by pets or humans.

Also, some chemicals can interfere with the germination of delicate seeds, preventing them from growing even when all other factors such as light and temperature are ideal. 

An Essential Well Water Test from Tap Score will analyse the general chemistry, hardness and alkalinity of your well water based on most of the heavy metals, minerals and pathogens mentioned in this article.

If you live in an industrial or agricultural area, consider an Advanced Well Water Test instead.

We recommend a simultaneous test of the nutrients, acidity and salinity of the soil to check for mineral build ups and pH levels that may have developed over time. Schedule an annual well water test, ideally during fall to allow for any adjustments before the growing season.

Water pH

The pH levels in your well water, when used for hydrating your plants, will modify the pH levels in the soil.

A low pH is acidic and high pH is alkaline or basic.

The pH of the soil plays a significant role in the plant’s ability to absorb nutrients. Some plants are more efficient in an alkaline medium while others perform better in high acidity.

While typical garden plants grow best in neutral (pH 7) or slightly acidic soil, many of the species suitable for waterwise gardens – lily of the valley, phacelia and lavender, to name some – do well in more alkaline soils.

As rainwater reduces the pH of the soil over time, some plants in high rainfall areas have adapted to highly acidic environments. Such is the case of azaleas, rhododendrons, camellias, daffodils and blueberries, for example. 

The minerals in hard water -calcium and magnesium- are alkalizing. This means that they contribute to increasing the pH in the soil. Seasoned gardeners can adjust the pH in the water or in the soil depending on the type of plants they are growing.

For example, mixing water with lime or wood ash will raise the pH, while adding sulfur or phosphoric acid will lower it. You can also purchase specially formulated solutions for alkaline or acidic results.

What is the best water for plants?

In a home garden, especially with potted plants that have no proper drainage, the best thing is to give them distilled water, which has a neutral pH. This way, you only hydrate them without worrying about keeping the nutrients perfectly balanced. However, this is a somewhat unrealistic option for simply watering plants, and in most circumstances tap water is suitable for plants.

Some alternative options include:

  • A water filter pitcher or one that uses carbon are good to remove minerals and chemicals without adding any new components.
  • Reverse osmosis filters provide clean and consistent water that will help your plants grow faster and stronger.
  • The water collected from a dehumidifier is cleared of any impurities when evaporated, which makes it a great option for your plants.
  • Another way to reuse water is to give your plants the water from your fish tank. Not only is this water conditioned to remove impurities, but it also contains animal waste that acts as a mild fertilizer.
  • Finally, rainwater collected from a bucket and natural spring water (not the bottled one you buy in a shop) have a lot of nutrients and are the closest to what the plants would receive in the wild, but give you less control to adjust the nutrients and pH levels for different species.

As mentioned earlier, water softeners increase the levels of sodium, so you should avoid these.

Is well water better than tap water for plants? 

Tap water is similar to well water in terms of quality for watering plants. The advantage of tap water over well water is that it is consistently maintained and the mineral levels are regulated by the US EPA. However well water has a lower fluoride content than tap water.

Tap water, as opposed to well water, is regulated by local governments who make sure that the hardness and pH levels are within the safety standards for human consumption. If the water is safe for humans, it is assumed that it is also safe for your plants.

The treatment that tap water undergoes is supposed to eliminate any dangerous heavy metals and bacteria, and the water supplies are often flushed to remove other contaminants that may leach or build up along the pipelines.

The chlorine added to kill microbes is seldom present in levels that can be harmful to plants, plus it can be removed by letting the water sit for a few hours until the mineral evaporates.

Still, you should check the annual reports for the quality of your city’s water to learn the values in which each contaminant is present and make sure that they are adequate for your type of garden.

Fluoride is commonly added into the city’s drinking water. As explained earlier, some plants are sensitive to fluoride and will develop brown tips over time.

Is well water good for vegetable gardens?

Whether your well water helps you grow a healthy vegetable garden depends on the hardness and pH levels in your well water.

Tomato and cucumber seeds are very delicate and will not germinate when exposed to certain chemicals present in pesticides, for example. The ability of a plant to produce fruits or healthy leaves depends on the nourishment it receives from the soil, which is affected by the minerals in the water you pour over it.

Basically, the quality of the water and soil will determine the quality of the vegetables you consume.

If there are any pathogens breeding in the well from which you water your vegetables, that will be absorbed by the plant and end up in your food. Any contamination in your well water will be dispersed throughout the entire plant, from stems to fruit, infesting your vegetables, potentially causing serious diseases in those who eat them. So, it is important to ensure your well water is safe for both you and your plants.

Final recommendations

Well water is exposed to a variety of elements that naturally occur in the soil, in addition to other chemicals and organic materials derived from human activity that can make their way into your private well.

Your plants are living creatures whose health depends on the nutrients they absorb, just as it happens with humans and animals.

If you have a private well, watering your garden with well water is the simplest option, especially if that is the water you drink as well. Thus conducting regular testing is advisable to guarantee that there are no harmful contaminants in your well that could be transferred to your plants, your food, your pets and yourself. 

Helpful tips:

  • Transplant your potted plants into different containers with healthy soil and change to rainwater or filtered water immediately if your well water is contaminated.
  • For outdoor plants, a few waterings with clean water should be enough to restore their health and flush out any contaminants.
  • Keep the water at room temperature to avoid stressing the root systems
  • Make holes to allow drainage and complement plants with the proper fertilizers
  • Watch your plants for any new signs of nutrient toxicity.

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