Build your own

June 10, 2010

by Kathy Klein, Victoria County Master Gardener Intern

edited by Charla Borchers Leon, Victoria County Master Gardener
Gardeners' Dirt

Editor's note: Today's article is Part II of a two-part series, and concludes the topic of "Self-watering containers" with information on how to construct them, set them up and plant them. Try this watering system in the hot summer days ahead.
Two tubs, a plastic container and PVC pipe have been prepared to construct a self-watering container.
LEFT:  Self-watering containers - construction and set-up - prepared materials
RIGHT:  Completely mulched in plastic and espaliered on a bamboo scaffold in a self-watering container, this cherry tree is trained for its future form.
Last week, I introduced the concept of self-watering containers with examples of my personal knowledge and experiences.

Today, I will take you through the steps to construct them, concluding with plants being watered in them.

My friend, Ele Chew, started me in this direction when she said, "Self-watering is the only way to go."

While it's relatively easy to build, explaining how is more difficult than the actual construction.

Using two molasses tubs (25-gallon size), designate one to be the lower tub, which will become the water reservoir. Designate the other molasses tub to become the planter, which will hold the potting mix and the plant.

You will need the two molasses tubs, a 1-gallon plastic container and 1-inch diameter PVC pipe to construct your self-watering container. Follow these step-by step instructions.


     *Drill 15-20, -inch diameter holes in the floor of the upper molasses tub at various random intervals to ensure water can drain out and air can circulate.

     *On the center-bottom of the upper molasses tub, trace the outline of the top of a 1-gallon plastic container that will hold your potting mix and which, when slipped through the hole, will protrude into the lower molasses tub and absorb water from the reservoir. The hole should be small enough that the top of the 1-gallon container remains inside the upper molasses tub.

     *Drill some pilot holes inside your traced line to start your saw. Saw the hole through, which you will fit the 1-gallon container, cutting inside the line you traced.

     *Drill at least three, -inch holes in the upper molasses tub beside the edge of the outline you traced in order to use cable ties to fasten the 1-gallon container securely to the floor of the upper molasses tub.

     *Use a hole-saw or 1-inch drill bit to cut an additional smaller hole through which the PVC pipe will extend from above the soil line and plastic mulch of the upper tub to rest on the floor of the lower (water reservoir) tub.


     *Drill numerous -inch holes in the bottom and sides to allow water to saturate the potting mix in the one-gallon container.

     *Drill at least three -inch holes, evenly spaced, around the side of the container, but at the top to align with the holes you drilled in the floor of the upper molasses tub for securing the 1-gallon container to the floor of the upper molasses tub with plastic cable ties. Attach to upper molasses tub floor with cable ties.


     *After inserting the upper molasses tub in the lower molasses tub with the 1-gallon container securely in place, determine where to drill the drain hole in the side of the lower tub just below the bottom of the upper tub to allow excess water drainage and prevent over-watering.

     *Drill into the side of the lower molasses tub.


     *Insert 1- inch diameter PVC pipe through the hole in the floor of the upper molasses tub so that pipe rests on the floor of the lower molasses tub. Mark where you wish the top of the PVC pipe to be, which will be higher than the rim of the top molasses tub. Consider the final height of your planting to help determine how tall to make the PVC pipe.

     *Remove the PVC and saw the bottom end at a 45-degree angle to ensure that water will flow easily into the lower molasses tub.


Once the elements of the container are constructed, place the lower molasses tub (the one that only has a drain hole in the side) in your desired location. Choose a flat place where the overflow hole can drain excess water. Consider using a plant dolly or similar apparatus to allow for easy movement of the container.

Place the upper molasses tub inside the lower tub. The 1-gallon container will rest on the floor of the lower tub. Insert the PVC pipe through the hole in the bottom of the upper tub with the sharp end facing down.


Pack the 1-gallon container with damp potting mix or damp peat moss. Fill the remainder of the upper molasses tub with moistened potting mix. To obtain a firm surface, fill to the container brim so the plastic mulch will not sag. The firm top surface makes installing the plastic mulch easy.


Plant just as you would if in the ground. Make sure you water in the plants only lightly. Remember, your potting mix is moist - and avoid over-watering.


Using it like mulch, secure plastic to the top of the self-watering container to prevent torrents of rain from entering your container and deluging your plants. Make one hole in the plastic for the plant and one to fit over the PVC pipe. Some plants, like blueberries, will send shoots up from soil level and plastic may hinder their growth, so use 6 inches of pine bark mulch instead of plastic. If you put multiple plants in one container, make a cut into your plastic mulch for each plant or rely upon large leaves to shield the container surface.


You are now to the point of finishing the process by providing water to your self-watering container. Pour water (preferably rainwater) into the top of the PVC pipe until water flows out the drain hole that you drilled in the lower molasses tub. Keep the lower water reservoir filled by pouring water in the top of the PVC pipe whenever needed. Never allow the reservoir to go dry.

Fertilize under the plastic annually, water the reservoir periodically and sit back and watch your plants thrive. You've just provided the ideal environment for your plant's roots. Success is on the way.
Two, large, empty molasses tubs from cattle feed
One sturdy, 1-gallon container or a pond basket
PVC pipe or electrical conduit
Plastic cable ties
Potting soil
Plastic sheet to cover the tub



Monday, June 14
Noon-1 p.m.
Dr. Pattie Dodson Public Health Center, 2805 N. Navarro St.
Free to the public
Bring your lunch and drink
Victoria County Master Gardener Lupe Cook will present a program on cacti and succulents.
The Gardeners' Dirt is written by members of the Victoria County Master Gardener Association, an educational outreach of Texas AgriLife Extension - Victoria County. Mail your questions in care of the Advocate, P.O. Box 1518, Victoria, TX 77901; or, or comment on this column at