Knowing when to water containers is often a head-scratching proposition, especially for new gardeners. While it's important to not let your container plant dry out, the bigger problem is often over-zealous gardeners overwatering their pots.
Now a new product is available that makes watering containers a little easier. The Waterstik is a probe that senses when the potting soil is too moist or too dry. Insert the probe into the soil at the appropriate level for that type of plant as indicated on the stick. In response to the soil moisture level, the Waterstik has a LED light on the top of the stick that blinks blue when the soil is too moist, green when it's ideal, yellow when the soil is dry, and red when the soil is dangerously dry. The Waterstik can be used on all types of plants from dessert cactus to tropicals.
For more information on the Waterstik, go to: Lee Valley.