Can You Water Plants With Stagnant Water?

All plants need good soil, good water, and a supply of healthy nutrients to grow and thrive. If the plants you are growing are for human consumption, like fruit and vegetables, then you should ensure that what you are feeding your plants will not cause any harm to your body. 

You can safely water plants with stagnant water. Stagnant water causes no harm to plants, but it can contain insect eggs, fungi, and microorganisms which are not healthy for plants or the humans that eat them. Always check for chemical contaminants before watering your plants with stagnant water.

Many gardeners collect rainwater in barrels or containers for use in their gardens, and some build ponds to collect excess water. Sometimes the water can become stagnant as it is stationary and is exposed to the elements. Plants need a good supply of healthy water to survive, but if your water supply is not fresh and has been standing for a while, can you still water your plants with stagnant water?

Should You Water Plants With Stagnant Water?

Your plants will not die if they are watered with stagnant water. Although plants do prefer oxygenated water, they will survive on a regular dose of stagnant water. The problem with stagnant water is that it can become contaminated under certain conditions or become a haven for breeding insects like mosquitoes. 

Various micro-organisms can thrive in stagnant water if the conditions are right for them. High nitrogen levels in stagnant water can cause plants to discolor and attract harmful insects to them.  Humans can become sick if they eat the infected plants.

Before safely using stagnant water on your plants, there are a few things you should consider.

Where Does The Stagnant Water Come From?

The water source is an important consideration when using stagnant water. If you are collecting rainwater in a barrel or container, it should have a tight-fitting lid to protect it from organic matter, debris, and natural light. If the top of the barrel is left open, debris could fall into the water and start to rot. If natural light is allowed in, organisms will breed in the water.

If leaves and debris fall into the water, they will sink to the bottom of the barrel or container, where anaerobic bacteria will break them down. The water will start to smell because the vegetation cannot survive in the water without oxygen. 

The water will then become a breeding ground for unpleasant bugs, but it can still be used to water your plants. It can take about 24 hours for the water to become stagnant, and mold and bacteria will grow in the water within 48 hours.

If the stagnant water is collected from a body of water like an old pond, there is a higher risk of contamination from fungi and breeding organisms in the water. Most open bodies of water like ponds will contain excess fertilizer run-off from your garden, which could have contaminants that could be harmful to your growing plants and to the people who eat the plants.

Where You Live Can Affect The Stagnant Water

Suppose the body of water is open to the ground around it, and you live in an area near industrial plants or open farmlands. The water could become contaminated by the chemicals used by the industrial plants, which could leach into the surrounding countryside or even into the local rivers and dams. 

Perhaps your farm neighbors have used fertilizers full of chemicals on their fields, and the runoff has dripped into your pond. Is the water safe to use on your plants? If you are not sure how contaminated the stagnant water is, purchase a water testing kit and test the water before you use it.

Will Plants Die If Watered With Stagnant Water?

There are times when all you have on hand is stagnant water to water your plants. While stagnant water won’t do any harm to your plants, what is living in the water could. Stagnant water could become infested with eggs from nasty bugs, or it could be contaminated with algae, moss, and mildew.

If the stagnant water is contaminated with fertilizers and chemicals, the contaminant could spread throughout the entire plant. The plant could become stunted or even die. If the plant looks healthy and is harvested for human consumption, the contaminants could be transferred to the person eating it, making them sick.

Sometimes, stagnant pond water can be beneficial to your plants. Decaying plant matter like leaves in the pond water could provide essential nutrients to your plants. Water a small patch in your garden first before watering everything. If the water is easily absorbed by the soil and does not lie on top and become smelly, it should be ok to use on all your plants.

Swimming pool water should not be used on your garden plants, especially if it has been standing for a while and is green and covered in organic matter and debris. Pool chemicals like chlorine will harm your plants! Don’t use the water, even if you skim off the floating debris.

How To Keep Fresh Water Fresh

When we think of growing produce or plants in the backyard, one of the items that we plan for is freshwater to keep our plants alive. While most of us would attach a hose to an outside faucet, this is not an option for many people.

The only way for water to stay fresh is for it to keep flowing. A flowing river or an artificial pond filtration system in your garden will keep water fresh and prevent it from stagnating. A filter will aerate the water and prevent organic matter and debris from flowing into the pond.

While planning your water catchment areas from rain, always factor in some way of protecting the water from the elements. If you can, use a lid over all barrels and containers to keep the water free from debris and free from algae that will grow in the water if light is allowed to enter.


Keeping plants healthy is the goal of most gardeners. Providing clean water is essential to the plant’s growth. How to provide that water is the job of the gardener. While most stagnant water is fine for watering your plants, it is not fit for human consumption, so never drink stagnant water!

Stagnant water may not always look healthy, but it will do the job and keep your plants alive if you don’t have access to clean water. 


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