Self-watering containers provide solution to South Texas gardening challenges

June 3, 2010

by Kathy Klein
Victoria County Master Gardener

edited by Charla Borchers Leon,
Victoria County Master Gardener
Editor's note: This is Part I in a two-part series on a solution to some of the gardening challenges in South Texas.  This article introduces the concept of self-watering containers and will be followed next week with how to construct them.
A row of self-watering containers on plant dollies graces the patio outside the Cuero Lumber Yard Studio. Bricks on each container hold lids in place regardless of wind conditions, and tub lids provide a mulching effect. Each espaliered tree also has a framework that is attached to the planter's side. These containers were constructed by Bruce Wright and are planted and maintained by artist Ele Chew.
Gardeners' Dirt
Blueberries requiring consistently acidic and evenly moist soil thrived well in a self-watering container. The PVC pipe (far left) served as a conduit for water to enter the bottom tub that became the water reservoir.
A self-watering container can be made from a discarded molasses-supplement tub used by cattle ranchers. The 25-gallon tub is a practical size for a container that can control soil and moisture requirements for most standard plants.
This self-watering containerized tomato plant produced fruit without damage from heat or water stress in last summer's drought and heat.
During my first year in South Texas, I planted a tomato plant, which subsequently succumbed to a nematode infestation.
The original blueberry bushes I planted were doomed because I planted them in the wrong type of soil and was unable to keep them "evenly moist."

And a gopher had the nerve to demolish my garden last fall.


At times, our Texas growing conditions make "evenly moist," "never allowed to dry out," "plenty of water" and other plant requirements, such as acidic soil, difficult to achieve. Container gardening can conquer these challenges; however, without an automatic watering system, maintaining correct water requirements in containers can be labor intensive, time consuming and a guessing game. Small containers are more difficult to successfully sustain than large containers. The size and cost of available containers may also be limiting to some gardeners' aspirations.


If you have encountered similar frustrations, consider making a huge "self-watering" container for your plantings. Specifically, consider a container made from discarded molasses supplement tubs used by cattle ranchers. Among the sizes available is a 25-gallon molasses tub, made from durable plastic. Once cattle have licked them clean, the tubs can be recycled into planters that provide a gardener with the ability to control soil requirements for selected plants, protect plants and provide moisture to plants' root zones.


" Self-watering" is not a 100-percent accurate statement because the gardener does the watering. However, the planters have a large water reservoir that provides sufficient and consistent water over a period of time, thus the gardener's watering decision, time and effort are reduced. Two molasses tubs are stacked, one inside the other. The resulting space in the lower of the two tubs creates the water reservoir.

Tubs shown here have a 5- to 7-gallon supply of water available to the plants. Water enters the lower tub through the tube, (in this case, PVC pipe or conduit), and saturates the submerged 1-gallon container, which in turn "wicks" the water to the potting mix in the upper container. Plastic "mulch" used to close or cover the top of the container (except for your desired plant) prevents weed growth and water evaporation, while at the same time, blocks excess water from drowning the plant when rainfalls are heavy.

The lower molasses tub has a hole drilled through the side at a water level, just below the bottom of the inside tub to prevent over-watering through the PVC pipe. Excess water runs out of the lower container hole when the reservoir is full.


There are various advantages to self-watering containers beyond the obvious benefits of better dealing with the South Texas heat and drought. These range from watering issues to those that affect the plant - and you, the gardener.

Watering issues - With the self-watering method, plants always have enough water, and there is less possibility of over-watering plants. Over-watering is one of the most common reasons for sick and dying plants.

This method is also environmentally strong, in that little water is wasted in evaporation and run off. Water is a precious natural resource that is a hot topic in Texas, and this system supports its conservation.

Plant protection - With plants closer to eye-level in raised container plants, it is easier to find insect pests, such as tomato hornworms, and to get rid of them. Plants and produce are also protected from diseases and soil-borne pests, such as nematodes and gophers.

Gardener rewards - With little waste of water as a result of this method, there is less watering time required by the gardener. Plants in taller planters and containers also mean less bending and kneeling. Harvesting tomatoes and other fruit and vegetables that grow in containers is much easier this way. And finally, this method is kind to the pocketbook with recycling, saving money and reducing trash that may have to be discarded.


Tomato cages, bird and grasshopper protection nets, trellises and supports for espaliered trees can be useful additions to a container. Even a mini-greenhouse from clear plastic and PVC may be an option for these large containers. There are as many methods and ideas as there are creative gardeners to put recycled molasses tubs to use.


My experiences in the use of self-watering containers proved successful with blueberries that required consistently moist, acidic soil. In the drought and heat of the past summer, my self-watering containerized tomato plant produced fruit without damage from heat or water stress.

Espaliered, or a dwarf variety fruit tree, if containerized and consistently trimmed and pruned, can live in a self-watering container.


*Once you have assembled the planter, added potting mix, set plants and watered, the planter will be very heavy. By placing the container on a plant dolly or old, decorative cart or wagon, you can move it should the need arise.

*Blocking access to the water reservoir may be advisable to prevent pests, such as mosquitoes or snails from contact with water.

*Potting mix is lighter than potting soil and has better drainage. Use potting mix, or better yet, special soil designed for self-watering containers. Listed in the side box is a recipe to make your own potting mix.

*The drain hole will keep the planter from becoming water-logged. The drain hole limits the amount of water in the lower container.

In next week's article, I will outline required materials for a self-watering container, how to construct one as well as suggestions on set-up. If a self-watering container will resolve some of your South Texas gardening challenges, then check back in to learn how to give it a try.
One part peat moss, vermiculite or perlite
One part clean, coarse builder's sand
A completely balanced, slow-release fertilizer (such as 14-14-14 added according to container size).
Lime may also be needed for certain plants to bring the pH to around 6.5.
Of course, your local nursery will have potting mix, and some will even have special mixes for self-watering containers.
Source: Texas Master Gardener Handbook

Nematodes and soil-borne diseases
Need to move plant seasonally, such as citrus or on patio to catch sunlight
Ease of access to plant for trimming, insect pest control and harvest
Poor or inappropriate soil
Control plant over-watering
Protection from invasion of other plants such as yard grasses, weeds
Lack of space for a garden or inability to use existing space for gardening

Source: Texas Master Gardener Handbook
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 vcmga@vicad.com, or comment on this column at www.VictoriaAdvocate.com.