By Jake Weber
Kansas State University Research and Extension
Container gardening has been a hot topic over the past several years. Yes, there’s a lot to be said about the value of container gardening. It’s a convenient way to grow vegetables and flowers, especially in unusual circumstances where conventional gardening is not possible.
Container gardening is not without problems. Extra care is necessary to ensure that the plants are able to grow well; the confined space of a container makes it especially difficult to manage the needs of the plants. Problems which complicate container gardening include crowded roots, increased heat stress, rapid depletion of soil moisture, and an exhausted supply of plant nutrients.
To do the job right from the start, you need to get the right kind of potting soil. The type of soil you use for your container garden must be porous enough to drain freely like coarse sand, and still have the ability to retain water and nutrients like a high quality garden loam. Unfortunately, garden soil is not suitable for container gardening, because it’s too “tight” and puddles badly in pots (proper drainage is essential for good air penetration into the soil which promotes healthy root growth). Good quality, homemade potting mixes can be made using garden soil mixed with sand and peat moss; however, it is often better to purchase commercially prepared potting mix instead.
Containers for the container garden may vary in style, size and material composition; the need for appearance may dictate which is selected. Homemade containers can be constructed with just about anything that will hold soil. Whether you purchase a commercially manufactured container or use one you’ve made, the only essential thing is that your container has holes in the bottom to drain away the excess water.
The size of container needed is determined by the size, type and number of plants that will be grown. It’s a balancing act to choose a container that will hold enough soil to meet the expected needs of the plants that will grow in it. A larger than necessary container may be needed if the plants are frequently exposed to gusty winds and intense sun. You may also need to choose white over darker colored containers to reflect sunlight which helps maintain a cooler soil temperature in those exposed locations.
Proper fertilization is essential for healthy plant growth; plant nutrients are quickly depleted in container pots. Nutrient depletion is not only caused by normal plant usage; it also results from leaching due to the need for frequent irrigation. Using a time-release type fertilizer in the potting mix is especially helpful for slow growing plants with minimal nutrient requirements; however, it is usually insufficient for supplying the needs of large, rapidly growing vegetable plants. These crops benefit from a fairly constant application of fertilizer supplied with the irrigation water.
Water needed for container plants varies with the type, number and size of plants, the volume of potting soil in the container, the weather, and the exposure of plants to sun and wind. It’s best to check the container soil every morning; do this by probing the soil with your fingertips about an inch below the surface. If the soil feels damp to slightly dry, it’s time to irrigate. If the soil feels moist, but weatherman says it’s going to be a hot, windy day, irrigate anyway. If the soil is wet and there’s water in the drain tray, you can hold off on the water that day. Here’s a rule of thumb; every time you irrigate apply enough water so that it flows freely out the drainage holes into the drainage tray.