In the April 8, 2020 edition of “Farm and Garden Notes”, the topic of container gardening was introduced.  Container gardening can allow people with limited equipment, experience, and available space to produce home grown vegetables. 

Today, I will discuss the use of sub-irrigated containers.  This relatively new twist to container gardening is gaining popularity.

Water can be a limiting factor in container gardening. Sub-irrigated containers can provide an even supply of water to the plants.  Sub-irrigated containers have a water filled compartment underneath the plants. The compartment is covered with a plastic screen. The potting soil in the container wicks a steady supply of water to the plants through capillary action. 

Sub-irrigated containers can be purchased at many retailers.  Common brand names include EarthBox and City Pickers.  Do it your self gardeners can make their own sub-irrigated container with common materials.  

I will provide some information to help you get started using sub-irrigated containers.  The sources for this article include the Mississippi State University Extension Service publication “Sub-irrigated Containers for the Mississippi Garden” and “Southern Gardening” videos produced by Dr. Gary Bachman entitled, “Sub-Irrigated Containers” and “Re-Planting Sub-Irrigated Containers”.

Soil

A potting soil mix should be used in sub-irrigated containers. These mixes can include peat moss, bark, coir fiber, vermiculite, and perlite. Common brand names of suitable mixes include Premier Horticulture Pro-Mix, Scott’s Miracle-Gro Potting mix, Baccto Potting Soil, Ferti-Loam Ultimate Potting Mix, and others. Never fill the containers with native soil removed from your lawn or garden.  

Fertilization

Lime and fertilizer should be added to the potting soil to ensure maximum plant growth.  One cup of pelletized dolomitic garden lime should be mixed per cubic foot of potting soil.  The lime will correct low pH values associated with potting soil mixes.  The soil should be added to the container in layers.  Add water to each layer before adding additional soil.  The soil should be mounded on top of the container to resemble a loaf of bread.

When filled, apply a narrow band of fertilizer along the side of the container.  The capillary action of the water will distribute the fertilizer.  The fertilizer should not be mixed in the soil.   Approximately one-half cup of a complete fertilizer should be used.  Examples include 8-8-8, 10-10-10, or 13-13-13.  A side dress application of fertilizer should be added during the growing season.  The addition of one teaspoon of calcium nitrate added directly to the water compartment will aid plant growth and help prevent blossom end rot.   Please note that water soluble fertilizers such as Miracle Gro should not be used with sub-irrigated containers. 

Planting

It is almost planting time!  A black plastic cover is provided with commercially produced sub-irrigated containers. The cover serves to prevent weed growth and conserve moisture.  After it is installed, cut a small slit in the plastic.  The planting hole can be dug with a trowel or bulb planter.  Dr. Gary Bachman recommends the use of a MaxBit.  This handy tool can be attached to a cordless drill.   Learn more about this Mississippi produced product at www.maxbit.com.  

Install your transplants and prepare for a bountiful harvest. Remember to fill your sub-irrigated container daily during the summer to ensure an even flow of water to the plants.

It is not too late to start your garden.  A sub-irrigated container garden may be just what the doctor ordered to produce a steady supply of vegetables this summer.

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