Window boxes help break up long expanses of wall with bright colored blooms. There are wooden and plastic window boxes, as well as basket-style window boxes that have moss liners. Window boxes have specific cultural concerns when it comes to watering, as they tend to dry out faster. A window box full of dying plants is a real concern, and lack of water is usually to blame. Watering the boxes properly helps ensure that the plants remain healthy and attractive throughout spring, summer and autumn.
Moisten moss liners in basket-style window boxes before planting. Soak the liner overnight in a bucket of warm water. Squeeze out the excess water; then mold it into the basket. This prevents it from wicking moisture out of the soil and away from the newly planted flowers.
Use a quality soil-less planting mix in window boxes. Using soil-less mixes provides the needed drainage to the soil so it doesn't compact and stop absorbing water. These mixes also provide aeration and retain water well so that the water is available to the plants.
Check moisture levels in the window box daily. Stick your finger into the soil to check the moisture. Water when the soil feels dry one inch beneath the soil surface.
Use a water wand attachment on your hose to provide a gentle mist of water instead of a stream of water, which may disturb plant roots. Avoid getting water on the foliage as much as possible, as this may lead to plant mildews.
Water until the water begins to drain from the bottom drainage holes, ensuring that the water has made it to the bottom of the box where the plant roots are. Spray off any soil that drips out onto the walls of your home, to prevent rust marks from forming as a result of iron in the soil.