Extension News

Better Blooms in No Time

Note to media editors:

This is the Garden Column for the week of July 20, 2007


By Cindy Haynes
Iowa State University Extension

July is the time when temperatures rise and some blooming plants in the landscape begin to languish. Below are some tips on how to keep those plants thriving and blooming throughout the “dog days of summer.”

Right Plant – Right Site
Many annuals and perennials, such as zinnias, geraniums and daylilies, bloom best in partial to full sun. If these plants don’t receive adequate sunlight, they won’t bloom well regardless of the amount of water or fertilizer they receive. So first and foremost, be sure your plants are sited properly.

Deadheading is one of the easiest ways to increase the number of blooms on many annuals and perennials. Simply remove the spent flowers before they have the chance to form seed. Deadheading prevents the plant from spending energy on seed production, allowing the plant to use its energy to produce additional blooms. For best results deadheading should be done frequently throughout the growing season.

Regular Water and Fertilizer
This is the tricky part. Too little or too much of either water or fertilizer can limit the number of blooms or shorten the bloom season for some plants. Applying the right amount of each encourages maximum flower production. 

Plants have different moisture requirements. For example, impatiens prefer a consistent supply of moisture throughout the growing season. Others, such as moss rose and vinca, are quite drought tolerant. Plants stressed from too little water often stop blooming. Too much water and they generally die – no blooms there! Checking the soil before you water is the best way to know whether a plant will need additional moisture. Another good rule of thumb is to remember that most annual flowers like 1 inch of rainfall or moisture per week during the growing season. Therefore, if rain has been lacking – water your plants.

The opposite is true for fertilizer. Too much fertilizer, especially nitrogen, can cause excessive growth at the expense of flowers. Too little fertilizer can limit growth, reduce plant size and thus limit the number of flowers. For most annual plants fertilizing with a complete fertilizer (low in nitrogen) once or twice a month is sufficient for bountiful blooms. For perennials, even less is needed. Fertilizing once, maybe twice, with a complete fertilizer (low nitrogen again) during the growing season is more than enough to keep most perennials blooming.

Pinching or Pruning
The benefits of pruning are not limited to woody plants. Some annual and perennial plants profit from the practice as well. Petunias are a classic example of plants that may benefit from being pruned or pinched back in mid to late summer. Simply remove one third to one half of the stem tips when the plants are looking leggy. In two or three weeks the plants will have initiated new “branches” and filled in their garden spaces. By then the flowers will be back as well and covering more compact plants.

Keeping your landscape full of flowers isn’t so hard. By following these tips many of your annual and perennial plants will reward you with abundant flowers throughout the growing season.


Contacts :
Cindy Haynes, Horticulture, (515) 294-4006, chaynes@iastate.edu Diane Nelson, Extension Communications and Marketing, (515-294-3178), dinelson@iastate.edu