Here are tips that can help sustain indoor plants while you're away.
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Many commercial products are available to water plants while you're away. Most consist of a reservoir and a wick you place in the soil. As the plant uses moisture, it draws from the reservoir. Also, adding water-retaining crystals to the soil will help plants during dry spells.
Another solution is to fill a washtub with gravel, fill the tub with water just to the level of the gravel, and set a plant on top of the gravel. The humidity from the water will prevent it from drying out. Another method is to set bricks in a bathtub, fill the tub with water to the level of the bricks, and set plants on the bricks.
A gravity-feed watering system provides moisture for several plants at one time. The water reservoir must be higher than the plants. Fill a large jar with water, and set it on a brick. Cut lengths of cotton or polyester rope that will reach from the bottom of the jar to the soil surface of the plants. Place one end of the rope in the jar and the other so it's resting on the soil.