Dr. Grow: A plant apart

Container gardening, a term in gardening circles that is quite popular right now, refers to growing flowers, vegetables and even shrubs in pots that are placed on a patio or deck. The containers used are traditionally clay pots, large plastic pots, concrete urns or some of the new lightweight expanded foam pots.

As you can see from the accompanying picture of Phyllis watering, my co-worker Dortha has interpreted the term container a little differently. She rescued the wheelbarrow I threw away and made it into what she calls a useful item.

I've been told that Dortha sometimes has an old bathtub sitting in her front yard that is full of annuals. My wife Marilyn has a friend who displays an old porcelain potty filled with petunias at her house. She and Dortha should get together and add a sink filled with pansies. Then they will have all the components of a modern bathroom right in their front yard, although it would lack the element of privacy.

No matter whether you use a clay pot or the kitchen sink there are some things that you should keep in mind when growing plants in containers. In the first place use a lightweight soil medium. I prefer a soil-less potting mix. This mix contains vermiculite, perlite and peat moss.

One potential problem with growing plants in containers is disease. Because the soil-less potting mix is essentially sterile, fewer disease organisms are present to infect plants growing in the container.

The soil-less mix is lightweight and very porous. Plant roots growing in this substrate can easily elongate and fill up the pot.

Watering is easily done because it fills up the soil pore spaces quickly. Be sure to water your container until you see water poring out of the weep holes at the bottom.

Once watered, do not water again until the soil feels dry to the touch. It is very easy to overwater plants in a container. Overwatering for a long period of time results in root rot, disease infection and poor plant performance. Overwatering is probably the cause of most container gardening failures.

On the other hand, porous soil-less mixes dry out rapidly. Leaving plants in containers unwatered while you are away on a two-week family vacation can spell disaster. Constant monitoring of water needs is essential.

Soil-less mediums lack most of the essential nutrients that plants require for vigorous growth. Therefore you are going to have to add these elements to the medium on a continual basis for plants to thrive.

I start by mixing one-half cup of lime to each gallon of potting mix. After planting I begin fertilizing with a root stimulator that contains high amounts of phosphorous and a rooting enhancer. I use this fertilizer one or two more times at weekly intervals.

From then on throughout the growing season, I use a combination of 20-20-20 and fish emulsion. I apply the combination each time I water my plants. Mixing directions are on the manufacturer's label. This combination provides most of the major and minor elements that a plant needs for vigorous growth.

I have occasionally seen plants in containers looking a little pale. When this happens, add some Epsom salts or magnesium sulphate to the fertilizer water. Plants will usually green up quickly.

Whether you are growing petunias or tomatoes in a pot or a bathtub, you can be successful. It is not that hard. Use the right rooting medium and water and fertilize correctly.