Water is a necessity for every living thing, but sometimes there can be too much or too little. Groundwater carries needed nutrients though a plant's roots to its foliage, flowers or produce in water, but too much water can rot the roots and deprive the plant of vital oxygen. Imagine water to a plant is like blood to the human body, a method of carrying nutrients and oxygen where needed.

The three stages in every plant's growth cycle include the seed stage, growth stage and reproductive stage. In the seed stage, the shell dissolves and germination begins. During the growth stage, the root system gets stronger and can support "life" above (usually after one to four months). The final stage, reproduction, brings flowers, fruits, pollen and seeds.

Test saturation in a potted plant by simply sticking your finger 1 inch into the soil near the roots. If the soil feels moist but not muddy, there is sufficient water to sustain the plant. You can also use a clean, wooden, unfinished dowel to stick into the ground. Check to see if the soil is pulling away from the sides of the pot, and if so, add water. Many home and garden stores sell various garden moisture meters that can test everything from the soil moisture to sunlight and soil PH levels, and many will work in either potted plants or gardens. On average, 1 inch of water per week is sufficient for most plants. Simple analogue rainwater gauges can help you judge how much rainwater your garden receives. If you are using a probe in a garden/lawn, remember to check various areas for moisture.

Knowing the type of soil, as well as the plants you are growing, helps when making watering decisions.

Loam soil, usually darker brown and "crumbly," will retain moisture with normal watering and is known for its benefits with garden flowers and small plants.

Sandy soil, light brown and "gritty," tends to drain very quickly, so it needs slower, longer watering. Sandy soil is not recommended for seedlings as it doesn't nourish the young roots as well.

Clay soil has small particles and is usually sticky to the touch when wet. It retains moisture but should not be overwatered as it does not drain quickly and can cause root rot. Do not mix sand and clay soils together as they will often clump, become concrete-like and limit the water and nutrition through the roots of a plant. Add compost or other organic material to sandy or clay soils for more effective moisture holding.

You can use normal tap water to water most houseplants unless the water quality is problematic (high chemicals, minerals, etc.). Distilled water can be used for the more sensitive plants that react poorly to the chemicals in tap water. While it may not be desirable for drinking or your pipes, iron levels in water are beneficial for watering most plants, so long as it is kept in a healthy PH range (level of acidity). Growing plants will feed on the iron in the soil to help with the process of photosynthesis, keeping the leaves greener and helping to produce oxygen. If your plants supposed-to-be-green leaves are turning yellowish, chances are you will need to add iron to the soil. PH levels range from 1 to 14. The most neutral is 7 -- the lower the number, the more acidic it is. Certain plants do best with higher acidity such as blueberries and azaleas; others prefer a more alkaline soil such as Shasta daisies and thyme.

As well as checking the moisture content of the soil, always keep an eye on the condition of the plant's leaves and stems. Leaves should generally be more green than yellow. If the leaves look wilted or are drooping uncharacteristically, or if the stems are bent over, it's a good chance that the soil moisture is wrong for that species. The water that travels up the roots to the stem, and the leaves or buds, helps to regulate the plant's temperature; the more the plant "sweats," the more water it needs to pull up from the ground.

All plants, even desert plants like cacti, require moisture to thrive. Keep note of all the factors above to learn the specific water needs of your plants.