by Ken Tilt, Dave Williams, and Bernice Fischman

Container gardening is different from in-ground plantings because the gardener has more control. This is both good and bad. Most of the physical requirements necessary for a plant to grow are provided by the gardener. Nature provides the light and carbon dioxide and you provide the rest. Although more work is required on your part, the rewards are greater because you are also in control of the show you create. You have access to all of nature's colorful pallet to create the design and the vision; you also have the tools and technology to provide the optimum environment to insure success.

Design factors are important as plants grow next to, in front of, in back of, or alongside other plants; and all grow at different rates. Things to consider are current and future dimensions, growth habit, texture, color, and how plants deal with sun or shade. Be aware of the needs of your garden and be willing to provide the necessary care. It is not the kind of gardening for the flippant who may water plants once a week or once a month or the gardener who feels that the main effort was in the purchasing and planting. Container gardeners must be aware of changes in season, knowing which plants will survive the winter and which ones must just be appreciated for their passing brilliance. For those who enjoy the results and not the process, professionally designed gardens can be purchased from your local garden center. You just need to provide care and maintenance. Keeping all of these things in mind, it must be said that well kept container gardens dramatically enhance outdoor living spaces and make special places for your family and friends to enjoy.

1. WHAT KIND OF POTTING MEDIUM DOES THE PLANT REQUIRE?

An old horticultural adage is that, "if you provide a good environment for the roots, the top will take care of itself." So, what you put in the pot is very important. Soil is not a good term to use because the majority of soils or top soils you would take from your yard have a texture that is too fine, stays too wet, and limits the amount of oxygen available to the roots. Soil can also introduce disease pathogens to the plant. It can be used and the plant will "survive" but it does not provide the optimum environment for the display you envision. You need to buy or concoct a well-drained medium that provides a good balance of air space and water holding capacity. The best option is to buy a "Professional" potting medium containing some of varying proportions of peat moss, vermiculite, perlite, coir, and pine bark. This route assures that you are getting a medium on which people's livelihood depends. You can buy potting soils off the mass market shelf but there is no regulation on what can go into a potting medium. Sometimes the pretty picture on the bag does not represent the results you get from the "stuff" you get inside the bag. There are some good products but try a small bag first to see if water moves through the pot easily and it does not stay too soggy after watering. There is no perfect medium. It is just one part of maintaining a good environment for the roots. The balance of water changes with the height of the container, how tightly the medium is compressed, the age of the medium and how often it is watered. It is not an exact science. This is the point at which the Green Thumbs are separated from the Brown Thumbs.

If you are going to conjure up your own mix, some good starting mixes would be: 3:1:1 Pine bark:peat:sand; 1:1 Peat:perlite; 1:1:1 Peat:perlite:vermiculite. Coir, which is a product that comes from coconuts, can be substituted for peat moss. If you are using free-standing containers which are subject to blow-over then add 10 to 20% sand. If the container is a window box or secured in some fashion to a deck or wall then do not use sand; it is too heavy. The pine bark you buy should have no pieces larger than 1/2 inch but should have some as large as 3/8 to 1/2 inch. If your pine bark medium is staying too wet or too dry, you can correct the problem by adjusting your watering practices or adding to your next medium more peat or coir (too dry) or more perlite (too wet).

These media do not provide many nutrients for the plant. You have to provide these by applying a liquid fertilizer that you get from any of your local garden centers. Follow the directions on the label. Look for products that provide "all" the nutrients needed. There are also "slow release" fertilizers available that allow you to make one application for the whole season. The acidity or pH of a medium is also a concern that must be addressed as well as adding calcium and magnesium to the medium. Simply stated pH refers to the concentration of hydrogen ions in a solution and is measured on a scale of 0-14 with 7 considered neutral. A low number means an acidic condition and a high number indicates alkalinity. If the soil is too acid or alkaline for particular plants, they cannot take up important nutrients, specifically nitrogen, phosphorous, potassium and 12 others in trace amounts. Most plants prefer a pH between 5.5 and 6.5. In an organic medium, adding 1 to 1.5 Tbs. of dolomitic lime for each 1 gallon of container medium will adjust the pH within range for a pine bark based media. This should be mixed with the medium or spread over the top of the pot medium surface and watered.

Media get spent over time and it is necessary to replenish. For containers of annuals - replace the media each year and when you add replacement plants. For perennial plants try to incorporate some new media at least once a year, and for other plants that are not to be re-potted remove some of the media and replace with a new mix when plants start to become root-bound.

2. WHAT KIND OF CONTAINER TO USE AND WHERE TO PUT IT?

Wood, copper, lead and terra cotta are well suited for container plantings because they are durable and also age with the plant. The new fiberglass pots look very good, are lightweight and last a long time. There are also decorative plastic pots for short term use. If using wooden barrels, it is wise to put plastic sheeting around the inside walls to help prevent rot. Make sure all large containers have large drainage holes at the bottom over which broken pottery shards are to be placed. There are large containers (suitable for small trees and large shrubs and many container garden designs), small containers for alpine plantings or one single plant, and window boxes. Containers can be placed on patios, decks, entrances to homes and businesses, in shady or sunny places. Each of these choices requires attention to plant selection and have special design considerations. Smaller containers and window boxes require more frequent watering and re-potting.

3. HOW TO CHOOSE PLANTS?

Read the tag, talk to your garden center professional, or look at mature specimens to see how large plants will grow and in which form they grow. Plants which work best together have the same basic physiological requirements. Do they need acid or alkaline medium? Are they sun or shade loving? What are their water requirements? Are their growth habits different enough to present an interesting display (large/small, short/tall, small/large leaves, small plain/large dramatic flowers, shiny/dull)? Consider how the plants grow and their form - whether they are upright, weeping, tufted, branching, climbing, prostrate, dense, airy. Small plants should be 1/3 the size of larger plants in one container. A great plant marriage is a trellis with a vine on it and a small shrub in front. Different cultivars of hosta make for fine marriages. You can design a successful grouping of individual pots. When grouping containers the triangular motif works well - incorporating plants of different heights. The selection of plants to use is only limited by your knowledge and imagination and their availability.

Examples of winning combinations:

4. HOW TO ARRANGE THE PLANTS?

Crowd in bedding plants. Plants don't like air pockets around them. No more than three colors in each container works best. Vary size and shape of flowers and foliage. Three main factors are: balance, color and shape/scale.

5. WHAT ABOUT MAINTENANCE?

Although assembly is not necessarily required, maintenance is critical. Water is necessary for the life of plants - not too much and not too little. Small plants and window boxes must be watered every 2 to 3 days and, if media does not hold enough water, daily watering in the heat of the summer is required. Large containers can often go 3 to 5 days without watering. As roots fill the pots and become pot-bound more water is required and is a sign that re-potting is needed. Most plants prefer a moist, not wet soil. Drip irrigation is an easy and preferable delivery mode as less water is used, leaves remain dry, and growth of fungal diseases on the foliage is minimized. Garden centers offer drip irrigation kits that are easy to assemble. There are also "self watering containers" that have a reservoir of water in the bottom to ease the maintenance requirements. With frequent, heavy watering, nutrients in the media will leach out water until you get about 20% leaching. Most flowering plants must be deadheaded frequently. Sanitation is important as dead leaves and flowers may spread disease.

6. HOW DO THE SEASONS AFFECT CONTAINER GARDENING?

Spring and summer are obviously the most prolific times for plants but the other seasons are capable of supporting evergreen plants. Use foliage (variegated or golden) color and berries for color throughout the year. Pansies and ivies at the base of evergreen shrubs will give your garden color before and after less hardy plants. Deciduous plants with interesting bark offer seasonal appeal: oak leaf hydrangea, stewartia, Hearts-a-Busting, kerria, coral bark Japanese maple, contorted willow, red osier dogwood or yellow-twigged dogwood, and others. Ornamental grasses are wonderful for offering year-round seasonal color.

OTHER SUGGESTED PLANTS:

7. AUBURN UNIVERSITY STUDENTS DEVELOP CONTAINER GARDENS

Students in the Herbaceous Plant Class at Auburn University (spring and summer sessions 1998) developed plans that addressed plant use, color, form, texture, design and scale. Principles of design were combined with an understanding of the habits of plants and their physical requirements. The horticulture students put their new skills and knowledge to the test by designing and planting window boxes and other container displays. This was a cooperative effort by the Horticulture Department at the University, The Alabama Extension System and generous sponsors: Buffalo Company, Inc., Euracast Caffco International; Fafard, Inc.; Village Arbors; Blooming Colors and American Designer Pottery. Auburn University faculty and staff involved in the project were Dee Smith, Ken Tilt, Dave Williams, Raymond Kessler and Bernice Fischman.

Designs were judged in the Funchess courtyard on August 14, 1998, by Master Gardeners, students, faculty and staff. Below are photographs of the top scoring containers as well as lists of the plants in each planting for the benefit of domestic gardeners, commercial growers, and nursery owners. Hopefully, if gardeners can find successful designs to use, this gardening feature will cease being a fad and become a standard feature in the home garden.

Below are photos (thanks to Donna Reynolds of Alabama Cooperative Extension Service) of the top scoring containers in random order:

Hibiscus rosea-chinensis-Chinese hibiscus
Bromeliad sp-Finger tip bromeliad
Pseuderanthemum atropurpureum
-Purple False Eranthemum
Coleus x hybridus-Coleus
Senecio cineraria-Dusty miller
Begonia x semperflorens-cultorum- Begonia
Thymus sp-Thyme
Origanum sp-Oregano
Ipomoea batatas 'Blackie'-Ornamental sweet potato
Ipomoea batatas 'Margarite'-Ornamental sweet potato
Coleus x hybridus-Coleus
Coleus x hybridus-Coleus
Begonia sempervirens-cultorum-Wax begonia
Portulaca grandiflora-Portulaca
Stachys byzantina-Lamb's ear
Pelargonium x hortorum-Geranium
Pelargonium crispum-Scented geranium
Catharanthus roseus-Annual vinca
Asparagus densiflorus 'Sprengeri-Asparagus fern
Catharanthus roseus-Annual vinca
Caladium x hortulanum-Caladium
Pelargonium x hortorum-Geranium
Zebrina pendula 'Purposii'-Wandering Jew
Setcreasea pallida 'Purple heart'-Purple heart
Catharanthus roseus-Annual vinca
Chlorophytum comosum vittatum-Spider plant
Gomphrena globosa-Gomphrena
Coleus x hybridus- Coleus
Senecio cineraria-Dusty miller
Ipomoea batatas 'Blackie'-Ornamental sweet potato
Sansevieria stuckyi-Sansevieria
Achmea fasciata-Living vase plant
Coleus x hybridus-Coleus
Caladium x hortulanum-Caladium
Peperomia scandens-Peperomia
Athyrium felix-femina-Lady fern
Coleus x hybridus-Coleus
Plectranthus-Plectranthus sp
Hibiscus rosa-sinensis 'Cooperi'-Chinese hibiscus
Ipomoea batatas 'Blackie'-Ornamental sweet potato
Salvia splendens -Annual salvia
Lonicera sempervirens-Honeysuckle vine
Ocimum basilicum
Coleus x hybridus-Coleus
Rosmarinus officinalis Rosemary
Thymus sp-Thyme
Ajuga reptans-Ajuga
Catharanthus roseus-Annual vinca
Caladium x hortulanum-Caladium
Asparagus densiflorus 'Sprengeri'-Asparagus fern
Hibiscus rosa-sinensis 'Cooperi'-Chinese hibiscus
Salvia splendens -Annual salvia
Catharanthus roseus-Annual vinca
Ocimum basilicum 'Minimum'-Dwarf basil
Rhoeo spathacea-Moses-in-the-cradle
Catharanthus roseus-Annual vinca
Zebrina pendula-Wandering jew
Coleus x hybridus-Coleus
Ipomoea batatas-'Blackie'-Ornamental sweet potato
Melampodium padudosum-Medallion flower
Thunbergia alata-Black-eyed Susan vine
Petunia integrifolia 'Purple Wave'-Purple wave petunia
Pelargonium x hortorum-Geranium
Senecio cineraria-Dusty miller
Verbena tenuisecta-Moss verbena
Evolvulus glomeratus 'Blue Daze'-Blue daze
Dracaena marginata-Dragon tree
Asparagus densiflorus 'Sprengeri'-Asparagus fern
Coleus x hybridus-Coleus
Impatiens wallerana-Impatien, busy lizzy
Pelargonium x hortorum-Geranium
Dracaena marginata-Dragon tree
Asparagus densiflorus 'Sprengeri'-Asparagus fern
Pelargonium x hortorum-Geranium
Catharanthus roseus-Annual vinca
Evolvulus glomeratus 'Blue Daze'-Blue daze
Thymus sp-Thyme

Books on the subject:
Malcolm Hillier - Container Gardening Through the Year
Thomasina Tarling - The Container Garden
Jeff Cox - Plant Marriages

Send questions and comments to bfischma@acesag.auburn.edu.

Letters to Bernice Fischman - 101 Funchess Hall - Auburn University, AL 36849.