Mid-summer is often the time of year when container plantings suddenly take a turn for the worse. Annuals that looked fantastic a few weeks ago suddenly look burnt, straggly, or maybe they’re just not producing as many blooms. Below I will detail the three most common causes of container planting failures.
When the spring rains subside and the summer heat sets in, plants in containers depend on us to supply them with consistent moisture so they can survive the hot summer sun. It is important to check outdoor containers for moisture daily until you get a feel for how often they require water. The best way to determine if plants need water is to feel the soil and water if it feels dry. It is best to actually stick a finger and inch or two into the soil, but if you don’t want to get soil under your nails, just feeling the top of the soil is better than nothing. Also, plants will often look droopy if in need of water. Soil in terra-cotta pots and hanging baskets (especially those with cocoa fiber liners) will dry out faster than soil in plastic or glazed containers. Also, containers in full sun will need more water than those in shade.
Too much water can be worse for plants than too little water. If the soil stays consistently soggy, plant roots are deprived of oxygen, fungus and disease spread more easily, and the plant may just rot and die. Again, the best way to know if plants need water is to feel the soil and only water if it feels dry. Yellowing, rotten looking leaves or the appearance of fungus on foliage often indicate overwatering. Make sure your containers have at least one drainage hole to allow excess water to escape. If your containers have a saucer to catch overflow, make sure to drain the saucer of any standing water after a few minutes.
Lack of nutrients
Fertilizing is not absolutely necessary, especially if your potting soil came pre-mixed with slow-release fertilizer, but regularly feeding container plants will definitely help them grow bigger and flower better. A lack of growth, reduced flowering, or dull color is a good indicator the plants need nutrients. Annual flowers are especially heavy feeders, so I recommend feeding them weekly or biweekly with a bloom-boosting water-soluble fertilizer. Water-soluble fertilizers are effective because the nutrients are immediately accessible to plants through their leaves and roots. Slow release granular fertilizers (like Osmoscote) are also easy to use and usually last for several months.
Fertilizers are labelled with three numbers. The first number indicates the percentage of nitrogen which promotes foliage growth (good for foliage plants like coleus and sweet potato vines). The middle number indicated the percentage of phosphorous which promotes flowering and root development. To keep annual flowers blooming all summer long, this is the number to pay attention to and should be the highest number on the label. The last number indicates the percentage of potassium which promotes all around plant health. Remember, plants in containers can’t access nutrients by spreading roots in the ground, so a little fertilizer from us is much appreciated!