Get It Growing News For 05/09/08
By Dan Gill
LSU AgCenter Horticulturist
Nearly any plant may be grown in a container outdoors as long as you provide the cultural requirements the plant needs.
Even commonplace plants take on a distinctive quality when grown in a container. You can choose from small-growing evergreen or deciduous trees, shrubs, ground covers, herbaceous perennials and annuals.
Indeed, containers filled with a variety of colorful, compatible plants are all the rage these days. In this planting style, plants are chosen almost as you would select cut flowers for a flower arrangement. The focus is on combining different plant shapes with colorful foliage and flowers in an aesthetically pleasing way.
Plant selection
Plants offer other considerations besides how they look (color, size, shape, texture). The amount of available light where the container is located is the most important factor to consider when selecting plants. Whether the location is sunny or shady, you must choose plants that will thrive in those conditions.
The hardiness of large specimen plants in big containers can be important. Generally, choose hardy plants that can survive winters outside in these situations so you won’t have to lug large, heavy plants and containers into protected locations when a freeze threatens.
Containers
A large variety of manufactured containers and found objects (varying in size, material, color, shape and design) can be used for planting. Only your imagination and taste set the limits.
Generally, try to use containers that are of muted colors and simple design, since brightly colored and heavily decorated pots will detract from the plants. In certain settings, however, you may feel containers with more elaborate decorations are appropriate.
Choose larger-sized containers whenever possible. Small containers are usually out of scale with outdoor landscapes and require more frequent watering.
Make sure the containers you use have one or more drainage holes in the bottoms to allow excess water to drain out of the pots when you water. This is critically important.
Soil
More than anything else, the soil or potting mix used in a container needs to drain well yet retain sufficient moisture to promote good plant growth. Make sure you purchase soil mixes specifically labeled “potting soil” for use in containers. Mixes labeled “top soil” or “garden soil” are not suitable because they are too heavy and will not drain rapidly enough. For the same reason, soil dug up from an outside garden bed is not suitable.
Many potting mixes are composed of peat moss, perlite and vermiculite in varying proportions. Their advantages are excellent drainage, light weight and good water retention. But they can dry out rapidly and may be hard to rewet when very dry. The main drawback is that they are relatively low in nutrients – a problem easily corrected by using slow-release fertilizers or soluble fertilizers.
Water
Plants growing in containers are far more dependent on you for adequate water than plants growing in the ground. When you water, water generously until water runs out of the drainage holes. Water again whenever the potting medium begins to feel dry to the touch or at whatever interval past experience has shown to be appropriate.
Watering frequency will vary depending on the type of plant, time of year, temperature and size of the plant in relation to the size of the container among other factors. Avoid allowing your plants to wilt before watering because this is damaging and can lead to bud drop or leaf drop.
If the potting mix becomes especially dry, it may be difficult to rewet it. Apply water until the potting mix absorbs and retains it. To facilitate watering, a soil level a couple of inches below the pot rim provides a space to hold water while it soaks into the medium.
Fertilizer
The roots of container-grown plants are growing in a confined space, and constant watering leaches nutrients rapidly from the soil. In this case, more frequent fertilizer applications generally are required than for the same plants growing in the ground. An adequate supply of nutrients is especially important when plants are in active growth.
The best choices for fertilizing container plants are either soluble fertilizers or slow-release fertilizers. Soluble fertilizers are easy to apply, especially when you use a hose-end applicator, but they must be applied every two weeks to maintain a constant supply of nutrients. Slow-release fertilizers provide nutrients over several months from one application so they cut down on labor.
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Contact: Dan Gill at (225) 578-2222 or dgill@agcenter.lsu.edu
Editor: Rick Bogren at (225) 578-2263 or rbogren@agcenter.lsu.edu