Your annual precipitation will help determine the best type of soilless potting mix for your mailbox planter. For wet to average rainfall, we recommend a mix that "does not" contain polymers as it may retain too much moisture and cause root rot and fungal problems. Miracle-Gro Potting Mix is a soilless mix that does not contain polymers, but does contain slow release fertilizer for easy care during the growing season. For drier climates, we recommend Miracle-Gro with Moisture Control or Pro-Mix Ultimate Container Mix. These mixes contain a water-saving gel or additives to hold extra water and reduce watering frequency. They also contain continuous feeding with slow release fertilizers. A weekly feeding of Miracle-Gro Bloom Booster will give your flowers the additional nutrients to encourage many larger blooms. All readily available at garden centers, home-improvement and discount stores.
Choosing plants with a cascading growth habit or shorter 4”-6” height varieties will work best in your planter. There are many choices with new varieties becoming available every year. Read labels for specifications and light requirements. For most common insect problems the use of SAFER Brand Insecticidal Soap is recommended.
Keep mailbox door free of growth by pinching back stems. Pinching will also encourage a fuller more compact growth habit.
In colder climates you may find it necessary to remove your planter after the holidays until spring. A cleaning with a hot solution of mild dish soap and bleach will do the job.
All other optional accessories are available thru various stores and on-line outlets.