Whether you have acres of land to care for or simply an apartment patio, container gardens can bring the outside right up to your door, for added convenience and beauty. All plants, whether corn or a petunia, have the same basic needs. Light, water, temperature, air movement, relative humidity and fertility all play an important role in plant health. Because container plants have their roots constrained in a pot, it is even more critical that environmental factors be managed properly. To have successful containers, consider some of the following critical issues.
PLANT CHOICE: This is one of the most important factors in having a successful container plant. Whether a perennial (think a standard rose, for example), a mixed container of annual flowers, or a pot with vegetables and herbs, do some research to understand the basic requirements of the plant and if you can meet them. Sun or shade? Cool season or summer? Fertile potting soil or extremely lean, porous soil (which is needed by now-trendy succulent plants)? These needs should be understood ahead of time to ensure a good start.
CONTAINER CHOICE: Is the size sufficient to provide space for adequate root growth? The plant may be small at first, but root growth may be extensive. This is especially important if growing tomatoes in a container, or a container with several plants in it. What is the material of the container? Porous wood or clay pots may lose water more quickly than plastic or glazed pots, and need watering more often. Make sure the container has adequate drainage holes. It is a myth that you can improve drainage in a pot with no holes by adding gravel to the bottom of the container. (I saw a tutorial on Facebook on this just the other day — further proof not to believe everything you see on the internet!)
Always use soilless media that is made for containers, not garden soil or top soil, which do not drain sufficiently in a pot. Some bagged potting media contains “water holding crystals,” which is worth having, as pots dry out so quickly in the summer. Thoroughly wet media before potting up, as it can be a challenge to get uniform moisture once in the container. A little trick, if you have a particularly deep container, is to put left over plastic cell packs or 4-inch pots at the very bottom, to take up space and save on potting soil. This is not to “improve drainage” (see above); it’s just taking up space at the bottom of a deep pot where roots would not reach.
Fertility is critical when plants are growing in root constricting containers. Best options include controlled-release, slow-release, or liquid fertilizers. The best fertilizer depends on plant needs: are you growing vegetables or flowers? Read the labels and follow application rates as described. Liquid can be used to supplement a slow-release if necessary. Many potting soils include some slow-release fertilizer, but these usually run out in 2-3 months, depending on the amount of watering the container receives and how warm the weather is.
PESTS AND OTHER PROBLEMS: Insect pests — such as aphids, caterpillars, and whiteflies — can be a problem on container plants. Scout plants regularly to catch any problem early, and use a “soft” pesticide, such as insecticidal soap, first for control. Another common problem in container gardening is the build-up of salts in the pot. Fertilizers, which are salts, can form a whitish, residual scum on the pot and soil surface, which can damage plant roots. A good watering (“flushing”) once a week or so should help rinse out the salts. Adequate watering — not too little, not too much — is another challenge of container gardening. Plants can recover more easily from too little water than from too much (rotted roots cannot be resuscitated). Keep in mind that a plant’s water needs may increase over the season, as plants grow and temperatures rise. Arrange for a plant sitter to take care of your carefully tended containers if you go out of town for longer than a couple of days, or you may return to crispy stems instead of lush leaves.
Containers can be a great way to add color, beauty, and maybe even fresh veggies and herbs, to your life. Check with Cooperative Extension for more information about growing successful container gardens.
Paige Burns is a horticulture agent with N.C. Cooperative Extension in Richmond County.