The most common problem with irrigation is adding too much or too little water.  How often and how much do I need to water indoor and outdoor plants? I used to use the touch method and if the soil felt dry then I would water or tried to water on a regular schedule. Going on vacation, I came home to find our houseplants were over watered and nearly died! So now we've discovered soil moisture meters. Several companies sell meters that you stick in the soil which measures moisture content.  The ETEKCITY soil water monitor currently sells for $8.99 with no charge for shipping by ordering from their website. Be careful when sticking the probe into hard ground -- use a screwdriver first to loosen the soil so the meter does not break. This 5-year old boy loves making measurements of soil moisture and growing native plants!