Regardless of the type of plants that you have in your home, watering house plants the correct way will determine the plant's overall health and life span.
Every type of plant has its own unique watering requirements. What works for one plant species may very well kill another member of your indoor plants garden.
Regardless of the specific name of your indoor plant, it falls into one of a few very basic categories. The category of a plant can give you a good idea of how to approach the watering process.
Water plants with water that is tepid. Many dislike being shocked with cold water - similar to how sudden cold temperature drops shocks them.
Foliage - Plants that you purchase simply for the appearance of the leaves: As a general rule, these house plants should be watered directly on the soil, near where the root balls would be located. Water foliage types thoroughly during the growing season from spring - fall and much less during winter. During winter allow a period of time when the top inch is allowed to become dry before watering again - which allows the plant it's rest period
Flowering - Those that you purchase for the sake of enjoying the flowers they will bloom: The soil for the majority of flowering house plants should be kept moist, but not wet all the times.
Succulent and cacti - Plants that have adapted to life in a dry climate: Regardless of whether these plants are used to living in dry climates or not, you still have to water them. From spring until fall I would suggest you water these so the soil is between moist and dry, then during the winter barely water them at all. Succulents and desert cacti store water for months in their foliage, so they need to be treated differently than other foliage and flowering plants.
There are different methods of watering that plants commonly prefer. To give your plant the best chances at survival, you should take the time to learn what it needs.
Top To Bottom - These plants (which is most varieties) prefer to have the root ball exposed to a large dose of water from the top of the soil. Push the leaves aside and add water for several seconds. Continue this until water runs out the bottom of the container.
Bottom - These plants prefer their water to be delivered from the bottom, which have root systems that grow close to the bottom of the pot. To give these indoor plants a watering, fill a saucer/tray under the container and wait for the plant to take the water it wants. Do keep in mind that most plants once they have had enough water - should have the excess water removed from the saucer or tray.
Immersion - Plants of this nature prefer to have their entire container placed in a standing sink of water for up to an hour. This gives these plants a chance to soak up what water they need. There are many plants that will enjoy this during the growing season once a month, as long as the excess water is then removed before it has to be placed back in it's displaying spot.
The simplest way to check if most plants need watering is to place the tip of a finger about 1 inch into the soil from the top. If it's still dry at the tip of the finger, then water. -- This is a general rule that does not apply to cacti and succulents, during winter.
How often should you water your plants? The answer to this is a complicated analysis that depends on several factors. Each plant's unique needs will change throughout the year.
Environment - Watering house plants of some varieties will depend on the environment they are in. Those in sunny windows will require watering more often than those in dark corners of office buildings.
Time Of Year - Plants often need less water during the winter and more during the times when they are blooming and growing. Adjust your watering accordingly to prevent root rot.
Species - Different plant types will frequently need water at differing intervals. Plants that need watering only once a week should not be soaked every day, so pay attention to the species requirements.
Different plant types may require special water sources. Pay attention to the details of the plant species to know what type of water to provide it.
Tap Water - Watering house plants of many species is fine with regular tap water. Keep in mind that there are chemicals in tap water, and some plant species will have adverse effects to these chemicals.
Hard Water - The added chemicals in hard water sources are often detrimental to plant health. If your home has hard water, consider using an alternate water source.
Rain Or Distilled - For those plant species that are truly sensitive, using rain water or distilled water is the only safe bet to keep them healthy.
Common signs of under-watering or over-watering on plants can tell you that the plant is going into shock. Look for these signs to know if you need to adjust the frequency of water that you are offering.
Dry Soil - If the soil of the plant is so hard that you can't feel moisture with your finger, then you need to water more often.
Brown, Crisp Leaves - Drying out like trees in the fall, plants often become crunchy and lose leaves when confronted with too little or too much water.
Refusal To Bloom - If a plant should be blooming, but isn't, it probably isn't getting the right amount of water.
Drooping Or Sagging - Plants that don't get the right amount of water often droop or sag.
Soggy Soil - Any time there is water standing under the plant or in the soil, the plant's roots may well rot away. This should be avoided in order to keep the plant alive.
Note: While this is a general guide - a grower should try and follow the specific advice for each species. You will find advice for watering for each plant in the A -Z list of plants here.