University of Illinois Extension

Container Garden Planting

Anything that holds soil and has drainage holes in the bottom may be transformed into a container garden. “Consider eye appeal, convenience, and cost when choosing a container,” recommended Nancy Pollard, U of I Extension horticulture educator. “Also think about how easy it will be to keep the plants healthy.

“For vibrant plant growth, the container must provide adequate space for roots and soil media for the plant to thrive. You should use containers of vigorous plants to provide focal points, divide outdoor rooms, create privacy, screen objectionable views, accent the landscape, or to grow tasty herbs, fruits, and vegetables.”

Pollard added that the choice of container--along with the choice of plants--communicates feelings and sets a mood.

“It can be amusing, a statement of value, clever, loud, quiet, classy, creative, solid, sophisticated, stylish, primitive, homespun, environmentally friendly, understated, matched, and more,” she said.

The choice of container material affects both the look of the garden and its maintenance. It is important to ask some questions during the selection process.

“Is the material porous?” she said. “In other words, will it soak up water? Clay or terra cotta soak up water. Wire baskets lined with absorbent materials soak up water. Peat pots soak up water. Porous material will lose water faster than nonporous materials. They can be lined with plastic to make the pot resistant to water loss.”

If you sink a porous pot into the ground and leave the porous rim showing, it will wick moisture out of the pot. Often the plants dry out and die because the water wicks out of the soil faster than it is replaced. So, if you sink a porous pot into the ground, be sure to completely cover the rim.

“Water in the pores of pottery will expand if frozen, cracking the pot,” she noted. “If a less porous material like rock or cement has a crack, then freezing and thawing of moisture will pry open the crack, making it worse.

“Protect pottery in the winter by thoroughly drying it out and covering it securely with plastic wrapping to keep it dry.”

Will the container you are considering be heavy to move? This can be addressed by placing the container on a dolly with casters in order to rotate it to take advantage of light or the need to move to a protected place during bad weather. “You can also place such a container in a permanent spot,” she added.

If the container is meant to hang either in the air, such as in a window or on a fence or rail, plan to water it more often. Winds and reflected heat will have a parching effect on the plants, causing them to dry out faster.

“The water may drip on people or possessions below so consider this possibility when determining placement of a hanging container,” Pollard said. “Secure hanging items well and consider potential safety issues when picking a spot.”

Will the materials, size, or color of the container being considered result in fluctuating soil temperature?

“Metal-container temperatures fluctuate more than non-metal ones,” she said. “Dark-colored containers absorb more heat than light-colored ones. Fluctuating temperatures are also a problem with small pots. These create bigger problems in the sun than in the shade. Dark-colored containers exposed to the intense summer sun can get hot. That heat transfers to the soil. If it gets too warm, roots are damaged and the potting media will dry out very quickly.”

It is important, she added, to protect the roots from extremes of heat and cold by lining the pot with foam or some other kind of waterproof insulation before planting if fluctuating temperatures are a concern..

Will the material rot over time? This may be the case with wood or other formerly living material. Treated lumber will last longer than untreated wood. Choose wood naturally resistant to decay. Examples are cedar and redwood from sustainable sources. Also consider safety issues if wood containers are hanging.

How much will it cost? Is it an environmentally friendly choice? Can it be reused or recycled? “If it is recyclable, clean the container with soapy water, and then disinfect it with a solution of one part chlorine bleach and nine parts water,” she said.