In my numerous conversations with people since starting this business 25 years ago, it amazes me how many of them give up on a plant they have paid good money for; they struggle to keep it alive for a couple of months, and then watch helplessly as it loses its leaves and dies. Since atleast 90% of buildings have enough light for some type of indoor plant or tree, correct watering is the only thing you really need to learn to keep your indoor plants healthy and attractive for many years to come!
To water a plant correctly you need to understand two simple concepts; the relationship between light and water, and how much water the roots need. For the average home or office with say 10 plants or less, less then one half an hour per week is all the time it takes to keep your plants in excellent condition. This is plenty of time to check each plant, and give its roots the water they will need to last another 7 days.
The key to all of this is knowing when the roots are dry, and the best way to determine this by feeling the soil and squeezing it in your hand: Moist soil clumps together, while dry soil is more powdery, and won’t stick together in your hand. Do this by sticking your hand 2 or 3 inches down, twice, once on each side of the pot. If it was watered evenly, it should be about the same in both places. When the soil feels dry and powdery, it is time to give your plant sufficient water that a little comes out the bottom of the pot. Plants with a softer looser soil is easy to test by hand, while other plants with tighter, harder soil texture may take more time, and effort.
Besides having a good sense of touch when testing the soil, it is also important to understand the relationship between water and light. Most people know that a plant dries out much faster outside on a bright, sunny day then a cloudy one, but many forget to apply this obvious concept to indoor plants. Most will be exposed to a combination of natural and artificial light. Naturally you want to maximize the amount of light your plant gets in a particular room in both the intensity (brightness) and duration (hours per day). The total average amount of light this plant receives on a daily basis will determine exactly how much water its roots need. As you care for this plant over an extended period of time, you will start to learn aproximately how long it takes for its roots to go from wet to dry, and therefore how much water it needs and how often. Naturally the goal is to avoid overwatering your plant ( most common cause of indoor plant failure). When you have overwatered by applying too much water, or watering too frequently, the roots will start to drown and rot because they haven’t had a chance to oxygenate, which requires drier soil.
On the other hand when allowed to dry out too long, the roots will also start to die, but your plant will give warning signs such as wilting or the sudden yellowing of several leaves. Then if you water it, the plant will generally recover quickly. In the case of overwatering however, there may be no visible warning signs until it is too late.
I hope this will help you care for you plants and keep them healthy. For more helpful tips and detailed information see part 2 of The Secret to successful plant care .