Getting the most out of your annuals and perennials isn't hard, states David Robson, University of Illinois Extension horticulture educator, Springfield Center, as long as you follow a few simple steps.
Flowers require an inch of water per week during summer months. When temperatures approach 100-degrees Fahrenheit, it may be necessary to supply two inches–split into two applications, three days apart. Water slowly to make sure water is absorbed into the soil instead of running off.
A drip irrigation or soak hose may be the best bet to place water where it's needed. These types of hoses need to be kept on for at least 8 hours to provide an inch of water. Most can be directed so only the soil gets moist.
Roses are heavy drinkers and may require at least two to three inches of water per week. Plants that are fertilized regularly will demand more water.
Avoid overhead watering with sprinklers or hoses especially after mid-morning. Water on flowers can increase diseases such as botrytis or gray mold. Avoid watering at night to cut down on diseases. Botrytis lowers flowering quality, length and quantity. Flower buds can abort. Overhead watering also increases foliage diseases such as leaf spots, black spots and leaf blights.
Use a soaker hoses where possible. If overhead watering is the only option, water early in the day, preferably between 6 and 9 a.m. Water is less likely to remain for any length of time on flowers and foliage and, thus, reduce the chance of diseases. Early morning watering also limits soil evaporation.
Mulching 4 to 6 inches with an organic source such as wood chips or compost will minimize soil water loss, keep the soil cooler and limit weeds and diseases. Avoid excess mulch as it limits air-water movement, and can lead to rots. Excess fresh mulch can also lead to slime molds, which look like dog vomit, but cause no damage to plants.
Dead flowers should be removed on plants as soon as possible to prevent seed formation. Once seeds start forming, flower bud formation is reduced. As far as a plant is concerned, seeds have top priority.
It's easy to remove, or "deadhead", larger flowers such as roses, geraniums, marigolds and zinnias. Smaller flowers such as ageratum and alyssum are more difficult, and seldom produce an abundance of seed. Many annuals benefit from a mid-summer pinching or pruning, particularly petunias and ageratum. Plants are cut back by a third to half in order to stimulate new growth. Pinching reduces the plant's legginess, common in petunias.
While it may be difficult to force yourself to prune, it will actually increase the flowering potential of plants. New shoots will form more flower buds. Plants will be stocky and less likely to break during wind and rainstorms.
Finally, annuals can benefit from a mid-summer fertilizing with an all-purpose garden fertilizer such as a 10-10-10. The ideal time to fertilize is after pinching or pruning. Water-soluble fertilizers are more likely to provide immediate benefits to the plants. Fertilize at the rate of one half (1/2) pound actual nitrogen per 1000 square feet. This works out, using a 10-10-10 fertilizer, to 5 pounds per 1000 square feet. After the application, water thoroughly.
