Houseplants have specific water requirements, which vary by species, location, temperature and type of pot. Automatic watering systems can help a forgetful houseplant caretaker maintain healthy plants but may result in over-watering or insufficient water for some plants. Even with an an automatic watering system, the houseplant caretaker needs to pay attention to the conditions of the plants and adjust the water if necessary.
Houseplants all have different water needs. Some plants need to get completely dry before you water them, while others should stay evenly damp all the time. When the top inch of soil gets dry, the plant should be watered. However, over-watering is often as much of a problem for houseplants as not getting enough water. Houseplants need more water in hot, dry conditions in summer and winter (heaters or furnaces dry air out). Also, unglazed clay pots leach water out of the soil. Plants with thick, waxy leaves (such as aloe vera) require less frequent watering than plants with many lush, soft leaves (such as geraniums).
Purchased Watering Systems
Commercially available automatic houseplant watering systems can be convenient, especially for caring for plants while you are on vacation. These watering systems use a water reservoir and a series of tubes and a timer to water your plants. The plants need to be gathered in a fairly small area, and the tubes are set up to go from one plant to the next. At each plant the tube has a small tap that is pushed into the soil. Each tap is adjustable, allowing you to provide more water to larger plants. The timer can be set to provide the amount of water your plants need. Depending on the system, this can be for up to two weeks, but the water reservoir will need to be refilled occasionally. The cost for one of these systems usually starts around $50.
Homemade Watering Systems
With a little planning and some aquarium supplies, you can make a homemade watering system similar to the commercially available ones. A homemade watering system uses aquarium tubing, valves and fittings, an aquarium pump and timer. You may need to do some experimenting with the timer and the pump to make sure you are not over-watering your plants. While a pump may be capable of pumping many gallons per minute, you want it to pump a fraction of that. Whether you are using a commercial watering system or a homemade one, you should never leave the first use until you are ready to go on vacation. Try it out for several weeks ahead of time to allow yourself time to get the adjustments right. This system may cost around $20 to $30, depending on the size of system you need.
Watering bulbs are usually made of glass with long, strawlike spouts that you stick in the dirt around the houseplant. The bulb is filled with water and as the plant dries out it wicks water from the watering bulb through the spout, keeping the plant uniformly damp. You may need more than one watering bulb for larger plants or for those in direct sunlight. You should check the water level in the bulb frequently and refill when necessary. You should also check the condition of the plant to make sure the water bulb is keeping it adequately watered and is not over-watering.
Watering plants by hand is the most effective and healthiest system to use if you are able to give the houseplants the attention they need. To water plants by hand, first check to see if they are dry. If they need water, avoid using straight tap water. The chemicals and salts in these systems can build up and kill your plants. Fill a container with water and let it sit for a day or two at room temperature to allow the chemicals and salts to evaporate. This will also adjust the water to the healthiest temperature for houseplants.
You should give the plants enough water so that some runs out the bottom drainage holes after a minute. If your pots do not have drainage holes, repot into pots that do--drainage is necessary for healthy plants.
Let the pots sit in the containers that catch the excess water for a few hours, then dump the excess water.