Tips to prolong annual flowers

Small yellow flowers in a red pot

By Dennis Patton

We have all heard the saying “April showers bring May flowers.”

The question is, how do I keep my flowers looking amazing for the rest of the summer? We plant annual flowers in containers and beds with the hope they will provide a pop of color throughout the season. Let’s look at what it takes to maintain that color boost up until a killing frost ends the season.

Like all good gardening practices, it starts with the right plant in the right place. Annuals come in a range of many sizes, shapes and colors. They also come with a range of options to choose from for best success in sun to shade. You should match the flowers needs to your location. A sun loving plant placed in the shade will not flower. A shade lover forced into the sun will likely wither in the summer heat.

Annual flowers that bloom all season long must be adaptable to heat. Annuals that thrive in the cool of the spring like pansies and kale will fade as June weather arrives. Popular summer annuals that love the heat include vinca, lantana, zinnias and marigolds. Given proper care these plants and many others will thrive once the summer heat arrives and continue to bloom until frost.

Annual flowers flourish and blossom best with good care. All require good drainage and consistent moisture. Container soil should be a commercially prepared potting mix which does not contain soil or dirt from the yard. Container mixes are formulated with various organic matter such as shredded pine bark, peat moss, coconut coir, perlite or vermiculite. These mixes hold large amounts of water and provide the oxygen necessary for root growth. Soil from the yard put in a container will be poorly drained and aerated, which will weaken growth.

By adding organic matter, compost or peat moss to your in-ground garden beds, you will grow bigger annuals. This adds water holding capacity and oxygen for root development. Growing good roots results in robust top growth and more flowers.

Don’t get in a hurry to plant summer loving annuals. Cool, damp soils will delay growth and lead to root rot. Annuals that thrive in heat are best planted after Mother’s Day. This gives the soil temperatures time to warm which will aid in root development.

Once planted, the next step for season long summer blooms starts. Annual plants are bred for one thing – to bloom. Annual flowers are heavy feeders. It takes a lot of growth to continually develop flower buds.

Fertilization should start at planting and continue monthly through September. It is almost impossible to over fertilize annuals as they produce flower buds at the end of a green vegetative shoot. Continual fertilization develops new growth, which creates new flowers. If growth slows so does flowering.

A fertilizer program is easiest when a soil test has revealed the missing needed nutrients. Since most people have not tested their soil, here are some basic guidelines. Prior to planting a bed in the ground, apply one pound of a fertilizer with numbers close to or like 10-10-10 per 100 square feet. Lightly work into the soil. Repeat this application monthly at one half this rate through September.

Smaller planting areas of five to six annuals or about 10 square feet and sprinkling one to two tablespoons of fertilizer around the plants. All fertilizer applications should be watered into the soil getting it down into the root zone where it can be picked up by the plant.

Container plantings require constant feeding for best repeat blooms. You have options. Water soluble fertilizers are convenient. Just follow labeled instructions for use. Granular fertilizers recommended above (10-10-10) work but you need to greatly reduce the amount applied to just a teaspoon monthly. It is hard to make a solid recommendation as container sizes vary greatly. The point is don’t skimp on fertilizer.

Many newer varieties are self-cleaning. This means they are bred not to set seeds. If an annual develops seed pods the plant puts its energy into seed production instead of flower production. Removal of faded flowers and seed pods, referred to as deadheading, stimulates new growth and brings more flowers. Deadheading keeps the planting neat and tidy. There is no set schedule but weekly might be a good guide to keep new growth stimulated and flowers coming.

Annuals have been developed to deliver flower power. Our goal is to give the plants what they need to maximize capacity for those amazing bloom displays throughout the summer. Right plant, right place, timely fertilization, a steady supply of water and deadheading are keys to success. Following these simple rules will result in not only May flowers but June, July, August, well into the final season ending killing frost.

Dennis Patton is horticulture agent at the Johnson County K-State Research and Extension Office.