[EDITOR’S NOTE: The following information is presented as an exclusive online supplement to the Nursery Market Report, SMALL SPACE SOLUTIONS: Pots With Pizzazz from the July 2001 issue of Lawn & Landscape magazine.]
CLEVELAND - The following are some guidelines contractors should follow when creating container gardens for clients.
ADDITIONS TO SOILLESS MIXES. Fertilizer is the most obvious addition to potting mix. Try adding a time-release fertilizer to the mix at planting.
Vermiculite and perlite also may be added to potting mix to increase volume without weight. Calcined clay can keep a mix loose and aerated, allowing deep, sturdy and healthy plant root structures to form. Hydrogels, or hydrophilic polymers, also may be added to prevent or delay water stress.
However, do not use more than the manufacturer’s recommended rate per container because plants can pop out of the soil in wet seasons if there is too much hydrogel in the mix.
PLANTS FOR CONTAINERS. With woody plants, select trees and shrubs that grow slowly, are smaller or dwarf in habit and are hardy to zone 4. Slow growers reduce the need for pruning and frequent repotting. Examples include Japanese maples, Kousa dogwood, star magnolia and Swiss stone pine. There are numerous small evergreen and deciduous shrubs also suitable for containers.
Certain ornamental grasses are well suited to container culture - particularly those with arching habit and those that manifest a degree of symmetry. A few to try include: Creeping Sedge, Leather leaf sedge, Blue oat grass, Japanese blood grass, Fountain grasses, Fescues and Maiden grasses for larger containers.
In general, perennials can be grown in containers if the root systems can be protected over winter. As a rule of thumb, choose smaller species and those that are not invasive in nature.
Like perennials, there are many annuals suitable for container culture. They are often mixed in containers, so make sure they are compatible when it comes to light exposure and watering requirements.
CONTAINER INSTALLATION. Steps in planting containers are relatively easy.
Make sure the container is clean, and soak clay pots in water for a few minutes before planting. Place a small stone, shard of pottery or coffee filter paper over the pot’s drainage hole to retain potting mix. The bottom few inches of large pots can be filled with crushed aluminum cans, plastic milk jugs or Styrofoam peanuts to reduce weight and the amount of potting mix needed.
Prepare your potting mix by adding amendments as desired, such as hydrogels and a slow-release fertilizer. Fill the container with this mix. Install plants as they would be planted in the ground. Water the container thoroughly after planting. Planting and watering should cause the media level to drop to ½ inch below the rim.
CONTAINER MAINTENANCE. Once planted, instruct the client to water completely so water drains through the drainage hole and runs off. On hot days, pots may need to be watered even twice daily.
If a slow-release fertilizer has been incorporated into the potting mix, no fertilizer may be needed the rest of the season. Some of these fertilizers last up to nine months. A water-soluble fertilizer also can be applied according to the label directions during the season.
Mulch can be applied over the container mix to conserve moisture and moderate summer temperatures. Apply mulch about 1 inch deep.
Depending on the plants, deadheading and pruning also may be needed throughout the season. Monitor frequently for pests, such as spider mites, because they can build up rapidly in containers.
END-OF-SEASON CHORES. At the end of the growing season after a killing frost, annuals can be removed from their containers. Also, containers should be cleaned to rid them of pathogens. Clay and plastic pots usually are scrubbed with a 10 percent solution of chlorine bleach in water.
The author is a horticulture extension agent, The Ohio State University Extension, Columbus.