Yard and Garden: Maintaining Container Gardens

AMES, Iowa -- Container gardens are an excellent way to grow plants in limited spaces. Horticulturists with Iowa State University Extension and Outreach offer tips on choosing containers and plants, and some ways to make sure they thrive. To have additional questions answered, contact the ISU Hortline at 515-294-3108 or hortline@iastate.edu.

How often should I water plants in containers? 

Watering frequency may vary considerably from container to container.  It depends on the size and type of container, composition of the potting mix, plant species, and weather conditions.  

Plants growing in containers should be checked daily (especially in summer) to determine if they need to be watered. If uncertain about the need to water, poke your finger into the potting mix. Water the container when the potting mix is dry at the 1 to 2 inch depth. Watering frequency may vary from once or twice a day (small container, hot windy weather) to once or twice a week (large container, cool weather).  

When watering plants in containers, continue to apply water until water begins to flow out the drainage holes in the bottom of the container.  

Do not allow the potting mix to dry out completely. Potting mixes shrink and pull away from the sides of the containers when completely dry. Dry potting mixes are difficult to moisten as water tends to flow between the potting mix and container and then out the bottom of the container (while the potting mix remains dry). Containers that have been allowed to dry out completely should be placed in a tub of water for 20 to 30 minutes to remoisten the potting mix. 

Do plants in containers need to be fertilized? 

Plants in containers need to be fertilized on a regular basis as nutrient levels in potting mixes quickly fall due to absorption by plants and leaching during watering.  

Many commercial potting mixes contain a slow-release fertilizer. However, slow-release fertilizers seldom last the entire growing season. When using a potting mix containing a slow-release fertilizer, begin to fertilize plants when plant growth slows or the color of the foliage fades. A granular fertilizer can be applied to the soil surface or plants may be fertilized with a water soluble fertilizer. Check the product label for application rates and frequency. 

What other types of maintenance do plants in containers need? 

Promptly remove dead leaves, spent flowers and other plant debris. Removal of plant debris improves the appearance of plants and lessens the likelihood of insect and disease problems.  

Inspect plants on a regular basis for insects and diseases. Control insects by either handpicking or by spraying/dusting with the appropriate insecticide. Control diseases by removing infected leaves or entire plants.  

Harvest vegetables at the proper stage of maturity for best quality and to encourage additional production.  

Remove spent flowers on annuals to improve plant appearance and encourage continuous bloom. Pinch back plants that get tall and leggy.  

If possible, move containers into the garage or other indoor location when severe weather approaches or when a frost or freeze is forecast.