BEST WATER For Plants. What You Need to Know

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Rainwater is the best water for all plants. Still, the unpredictability of rainfall’s timing and volume means other additional sources are needed. Water quality and security are fast becoming essential considerations for cities, farmers, and gardeners. 

The Tale of Tap Water

Water is a precious finite resource. Providing drinking water to growing populations is challenging, and up to 30% of household consumption of tap water goes down toilets.

The U.S. Public Health Service established guidelines for the bacteriological quality of drinking water in 1914, marking the beginning of federal control of drinking water quality. The Safe Drinking Water Act came into effect in 1974.

Most municipal water systems use groundwater, rivers, and surface water for water supply. The water quality can vary based on supply, distribution systems, and initial contamination levels. 

Before using tap water, ensure you are aware of its quality. As mentioned above, water quality is strictly regulated, and you can be reasonably sure of its suitability for human health. Still, even a low concentration of salt can affect plant health.

Water public water systems use a combination of ozone treatment or UV radiation, filtration, ferric sulfate, calcium hydroxide, active carbon, and chlorine to purify water of possible harmful microorganisms, chemicals, and other contaminants.

Since salts are needed to soften hard (lime-rich) water, softened water can include excess, which impacts a plant’s water absorption ability.

Whatever your water supply, consider using a filter that includes active carbon filters. These fit under the sink or directly on your tap water supply valve.

Testing Drinking Water

The quality of your tap water is only partially the responsibility of your supplier. They must ensure the water is safe for drinking and avoid health risks. Their concerns center around taste, color, and contamination, not plants.

Nitrate is a growing concern as nitrogen users flood water systems with it to extract bigger yields from soils that lack biodiversity. Sodium is an increasing problem as changes in aquifer levels draw saline water in. The indiscriminate use of fertilizers and soil erosion also contribute to high sodium levels.  

Tap water tests generally focus on natural minerals in the water. Water’s most common dissolved minerals are sodium, calcium, magnesium, potassium, chloride, bicarbonate, and sulfate. 

Bottled Water

It always fascinates me to read the label on bottled water – bottled at source. Bottled water is commonly used as drinking water based on the belief that it is healthier. 

Most countries regulate the industry closely, and misbranded products are severely penalized. Any statements, such as bottled spring water, must meet the requirements of the applicable standards and be void of any health risk.

Mineral water, for instance, must:

  • Contain at least 250 ppm total dissolved solids

  • Come from a water source at one or more bore holes or natural springs

  • Originate from a protected hydrogeological source

  • Contain no added minerals

There are similar definitions for bottled:

  • artesian water

  • bottled water

  • deionized water

  • distilled water

  • drinking water

  • groundwater

  • purified water

  • reverse osmosis water

  • sparkling bottled water

  • spring water

  • sterile water

  • well, water.

A product must be misbranded by the appropriate name reflected in the applicable identity definition standard.

Watering more than a few houseplants with bottled water is economically impractical. Use bottled water for the human body, but please recycle the bottles. 

Bottled Spring Water as an Alternative to Tap Water

Please read the label of any bought water. The bottling companies are obliged to declare the actual mineral content. Also, spring water is a more eco-friendly option.


According to

Bottled water facilities perform water testing daily to conform with their respective EPA and FDA regulatory requirements for minimum water testing frequencies. 

*Bottled water is tested for total coliform bacteria at least twice as often as tap water. In some cases, bottled water testing is done up to 36 times more often than tap water on a gallon-for-gallon basis. 

[*FDA: 21 CFR 129.35(a)(3)(i) / USEPA: 40 CFR 141.21(a)(2)]

If you’re concerned about water quality and health risks, check out this CDC link on water and health topics, remembering freshwater rules.

Collecting Rainwater

As earlier stated, rainwater is the best water available for your plants. A water harvesting system is economical and ensures your plants get the best. Harvested water should not be drunk but would be fine for garden purposes.

You can do water harvesting by connecting your gutters to tanks. I have seen a system connecting several 500-gallon tanks in a series to serve a community garden with enough water throughout low rainfall.

Algae and microbial activity will be minimal if you ensure the tanks are dark-colored to avoid light penetrating. Still, it is not fit for human consumption as it could pose health risks but provides a garden with more water than is required. Any microorganisms will complement the biome in the soil.

How Much Water Soes A Garden Need?

Although a rainwater collection system can reduce dependence on water, they only work if you can harvest and store enough. A 10 x 20-foot garden needs 200 gallons of water per week, so a 500-gallon tank will hardly last three weeks.

Still, a well-designed system with low-cost solar pumps and multiple tanks can take your garden off the grid. The system allows you to pump any harvested water to the furthest tank for storage, lessening the risk of running out and conserving energy. 

You can spread the cost over time, adding new drums to the system annually. Healthier water helps you produce healthier plants rich in nutrients, giving you a competitive advance if you sell your product.

If you are averse to using plastic tanks and have land space, consider adding a series of ponds or a type of water catchment basin.

To minimize evaporation, these can be lined with a permeable membrane and filled with rock to create your micro aquifer.

Harvesting Water In Ground Basins

Water across the property will flow to the lowest spot and fill the hidden development. This might take some construction and plumbing know-how, but it is doable.

If you go the whole hog, connect humidity sensors that monitor the soil around your plants to a submersible solar-powered pump for a drip-feed, irrigate-on-demand system.

Sustainable Food Systems

The world is fast changing, and our family’s growth and health depend on high levels of awareness and a drive to produce solutions.

In a sustainable food system, plants will play an increasingly important role. Those with an independent hidden water source will best be able to navigate this risk.

When it comes to the best water for plants, rain takes the trophy, followed by harvested rain in a close second. While few of us can access streams and lakes, we can all harvest rain, plant gardens, and irrigate them with our water reserves.

Plant Water Availability

At the risk of sounding patronizing, the best water for your plants is water you can access. Several factors influence water availability.

Proper Watering

Improper watering methods can see our plants either overwatered or underwatered. Underwatering usually happens when we haven’t calculated the time it takes to cover a given surface size with an inch of water. This, of course, is influenced by the water’s flow rate.

A ten-foot-long bed four feet wide (40 square feet or 5,760 square inches) would need 5760 cubic inches of water to saturate the soil, ensuring the deepest roots get water. That’s almost 25 gallons of water. (231 cubic inches to a US gallon).

For a bed of similar size in the metric system, say, 300 cm x 120 cm = 36 000 cm2. If we were only water a centimeter deep, that would be 36 liters. Still, we need to water about an inch (2.5cm), so we need to multiply the 36 liters by 2.5, giving us 90 liters.

Light Sprinklings Don’t Work

It is harmful to sprinkle plants every day lightly. Frequent light applications wet the soil to less than an inch, and most plant roots go much more profound. Light sprinkling only settles the dust and does little to alleviate the drought stress of plants growing in hot, dry soil.

 Instead of light daily watering, give plants a weekly soaking. When watering, let the soil wet to 5 to 6 inches (about 15 cm).

This watering allows moisture to penetrate the soil where roots readily absorb it. A soil watered deeply retains moisture for several days, while one wet only an inch or so is dry within a day.

In contrast, some water so often and heavily that they drown plants. Symptoms of too much water are the same as those of too little.

Leaves turn brown at the tips and edges, then brown and drop from the plant. These symptoms should be the same since they result from insufficient water in the plant tissue.

Root Rot

Too much water in the soil causes oxygen deficiency, compromising root health. Like all living things, plant roots need oxygen to live. When soil is continually wet, anaerobic conditions cause the roots to rot, affecting the whole plant’s health.

The leaves begin to show insufficient water as the roots and xylem become dysfunctional, causing ill-informed gardeners to water even more, further aggravating the situation and causing the plant to die quickly.

Thoroughly moisten the soil at each watering, allowing plants to use the available water before adding more. Overwatering or improper watering is the leading cause of plant deaths, especially indoor plants.

How To Irrigate

I have purposefully not included spray irrigation as it wastes too much water. I’m biased against the two systems below.


One of the earliest types of irrigation is flooding. It is frequently employed in regions with intense summer heat, particularly in extensive farming operations. Still, it can be effectively used in the backyard garden.

A small dam wall first surrounds the area that has to be watered before flooding the bed.

Flooding removes these extra soluble salts from the soil by leaching (flushing them down). Flooding is best performed before spring planting, tilling, and fertilizing.

Flood irrigation has risks if not well managed. Use the calculations above to add only the required water to prevent drowning your plants and wasting water. Also, runoff is challenging to avoid.

Drip Watering

The trickle or drip irrigation watering method is superior to those mentioned above. It uses a little water over an extended time, typically several hours. It is the controlled, slow application of water to the soil.

Drip Watering Systems

The water flows under low pressure through a plastic pipe or hose along each row of plants. The water drips into the soil from tiny holes, which are either precisely formed in the hose wall or in fittings called emitters plugged into the hose wall at the proper spacing.

Drip irrigation water vegetables, ornaments, fruit trees, shrubs, vines, and container-grown plants outdoors.

In Closing

Low-quality water for plants is water with too much salt or chloride. Adding an inline filter can help remove unwanted elements and permit you to give your plants what they need. This is especially important if your’ watering containers or growing trees.

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