Flower Boxes Drain

How much water are you going to pump into the flower box? Most cases just let drain back into ground. Or have some sort catch basin under the flower box with pipe going to flower bed to keep some of the water from going to waste.

letting it drain away is the most natural method except in cases like dolomite where the dissolved CO2 from plant material is a strong enough acid to dissolve the dolomite or chert and eventually create sinkholes.

To avoid other complications and wasting of water the irrigation applications should be limited to the water requirements of the plants.

See Popular Mechanics for their "10 Best" Inventions for 2010. A man developed a planter which has several features which help to conserve water. What's more, there's a lid which works by trapping water vapor rising from the plant, usually at night, and providing downward sloping channels for the water droplets to collect upon, and eventually to roll down to drop down into the soil again! Depending upon the temperature and humidity of your location you may save an incredible amount of water AND have no water to drain at all!

If the flower boxes are quite large you need to consider what will happen when the boxes are inundated with water during heavy rainstorms. Letting the water drain away into the soil naturally would be best, but when there is an excessive amount of water it will cause erosion where the water hits the ground. Consider having a decorative rock feature or sculpture for the drain water to splash against to help dissipate the energy and to disperse the water over a larger area, to avoid erosion.

http://www.google.co.uk/search?q=watering+flower+boxes&sourceid=ie7&rls=com.microsoft:en-US&ie=utf8&oe=utf8&rlz=1I7GPCK_enGB411&redir_esc=&ei=licdTfn3FoW6hAe1-pS3Dg