Basic container gardening

By By Gail Barton / horticulture columnist
June 15, 2003
I've recently made additions to my deck and am spending a lot more time there. During my lounging time, I've grown fond of the deck pots that are my constant companions.
Planting in pots or other containers is the perfect gardening method on decks like mine.
Their portability allows the gardener to create a focal point at the front door or to bring herbs closer to the kitchen.
For ease of watering, I use fairly large containers at least 12 inches in diameter. During extremely hot weather, small containers quickly become pot-bound and may need to be watered twice daily or more.
For best results, a container must have holes to allow for drainage of excess water.
Plant roots need air as well as water. If potting soil becomes water-logged, disease and death will result.
All containers, even those with several drainage holes, can hold too much water unless precautions are taken.
To avoid the problem, use a soil-less mix or potting soil made mostly of peat, ground bark and drainage-enhancing ingredients like perlite and vermiculite.
Watering, fertilizing
Watering is the biggest maintenance task. I teach my students to follow these watering rules for best results:
Water thoroughly when needed. A good thorough watering should allow water to run out of the drainage holes in the bottom of the pot.
This will completely soak the soil and wash out salt buildup from fertilizers.
Break the force of the water by using a nozzle or rose. High pressure watering blasts soil and fertilizer out of the pot and leaves dry spots in the soil.
Allow the top inch or so of soil to dry out before watering again.
Never leave a pot sitting in a saucer of water. This creates an artificial swamp and generally causes disease. I don't use saucers under outdoor containers unless we are in a severe drought. In that case I remove the saucers when rainfall resumes.
Add a water-holding polymer to summer containers. This material is sold under the brand names Terra-Sorb or Soil-Moist. It looks like rock salt when dry.
After taking on moisture, the product expands looks like clear Jell-O. It works by creating timed-release water reserves in the soil without filling the air spaces roots need to grow.
Container plants need low rates of a fertilizer with trace elements. Without trace elements like calcium, iron and zinc, potted plants can exhibit yellowing, stunted growth.
I like to either use a liquid fertilizer or a granular slow-release fertilizer.
If you choose the liquid fertilizer, apply it at a low rate once each week. The slow release should generally last in the soil for three months or more.
Read the label to get an indication of how long your fertilizer will last.
Choosing plants
Now for the fun part plant selection. For constant interest, don't just think about flowers, select plants with attractive foliage.
Choose plants with attractive disease-free leaves and incorporate a variety of leaf textures and sizes. Include some plants with variegated leaves, unusual foliage color or scented foliage.
I've found that an assortment of plants with different heights and growth habits provides attractive tiers of height, color and texture. I generally select from the following three groups:
One tall plant (like pentas, angelonia or red fountain grass) for the center of the pot.
A group of three short to medium-sized plants (like annual periwinkle, narrowleaf zinnia or coleus).
At least three trailing plants (like Cuban oregano, ornamental sweet potato or purple heart) to dangle over the edge.
Any container planting is a temporary growing arrangement. Even under perfect maintenance, plants eventually become pot-bound and listless. Container plantings rarely make the transition from one season to the next without being repotted.
In spite of the maintenance and limited life, I've found nothing else that enhances my deck life like my pots.
The maintenance time I spend on these containers yields hours of enjoyment.