It is not unusual for annual flowers, such as impatiens and petunias, to look a bit peaked about the middle of summer. For some plants, such as pansies, stock and snapdragons, stress from summer heat turns off the initiation of flowers. But most flowering annuals are fairly heat tolerant and can be revived with a little pinch of their stems and a sip of nutrients.
Though for the most part, our temperatures haven’t been all that stressful this year, most areas have had substantially heavy rainfall. Such heavy rains can wash away much of the available nitrogen, making it unavailable for plant uptake. Plants that are becoming deficient in nitrogen will often look a bit pale, or in more serious cases, the leaves will turn yellow, beginning first with the older, lower leaves. If left uncorrected, the deficiency will begin to affect the new growth, resulting in stunted, pale leaves. Though nitrogen generally is thought to promote foliage growth rather than flowers, plants that are under stress from lack of nitrogen may bloom sparsely or not at all.
Containerized plants are especially vulnerable to leaching, since proper watering procedure calls for enough fluid to be applied so that some runs out of the bottom of the pot. This helps ensure that water moistens the entire soil area. But this method also washes some of the nitrogen away with each watering.
A bit of supplemental fertilizer, applied alongside the plants, can rejuvenate your tired plantings. The amount to apply varies with the specific product, formulation and plants. As a general rule of thumb, you can use one-half to 1 pound (1-2 cups) of 5-10-5 fertilizer per 100 square feet, but be sure to follow the label directions for your particular product. Be sure that any of the dry fertilizer is rinsed off of the foliage as soon as possible to avoid burning the plants.
Feed starved containers with a water-soluble product, diluted according to label directions. You can either use a very dilute solution with every watering, or use a bit stronger solution once every week or two.
For most annual flowers, pinching the plants back about halfway will encourage more branching and, in turn, more flowers. The plants may look a bit raggedy initially after being cut back, but with a little water and fertilizer, you’ll be rewarded with a much more attractive plant.
Removing the faded blossoms from annual and perennial flowers, which is often referred to as “dead-heading,” is another good gardening practice. Dead-heading will help encourage more blooms, by preventing seed pods from competing for the plant’s food supplies. The plants will also be more attractive with the old, spent blooms removed.