Deadheading in September: What to Cut and What to Keep

Northern Colorado gardeners can tidy fading flowers while leaving valuable habitat and winter interest

By North Forty News Staff | NorthFortyNews.com

September can tempt gardeners to start cleaning everything up.

After months of flowers, heat and fast growth, some garden beds are beginning to look tired. Blooms are fading, stems are leaning and seed heads are replacing the bright colors of summer. But before reaching for the pruning shears, Northern Colorado gardeners may want to be selective.

Deadheading — removing flowers after they fade — can improve a plant’s appearance and, earlier in the growing season, encourage some plants to continue flowering. The basic principle is simple: flowering plants expend energy producing seeds, so removing spent blooms before seeds develop can redirect some of that energy.

But as fall approaches, the reasons for leaving flowers and stems standing become increasingly important.

September Changes the Equation

During spring and summer, annual flowers are among the easiest candidates for regular deadheading. Removing faded blooms from many annuals can help maintain their floral display instead of allowing the plants to put their energy into seed production.

Perennials require more judgment.

Some perennials look noticeably better after their spent flowers are removed. Others produce attractive seed heads or provide food and shelter for wildlife.

That distinction becomes especially important late in the season.

Standing perennial stems can provide overwintering habitat for beneficial and native insects. Seed heads can also become a food source for birds. Instead of automatically cutting every fading plant to the ground, gardeners can consider what each plant contributes after flowering ends.

Three Common Ways to Deadhead

How a flower should be deadheaded depends largely on how it grows.

Plants that send up relatively unbranched flower stalks can generally be allowed to finish most of their display before the stalk is removed near the plant’s base. Delphiniums are one example.

On plants with branching flower stems, individual faded flowers can be removed by cutting their stems back to the main stem. Black-eyed Susans, or Rudbeckia, can be treated this way. Once the entire stem has finished flowering, it can be removed.

Flowers such as daylilies can be even simpler. Individual spent blooms can be picked from the stalk as they fade.

Whatever the plant, clean, sharp bypass pruners or garden snips make the job easier.

Don’t Deadhead Everything

Sometimes the best September gardening decision is to leave a fading flower alone.

Gardeners hoping a favorite plant will reproduce from seed shouldn’t deadhead it. Removing the flower before seed development defeats that purpose.

Seed heads can also add texture and structure to a garden long after summer flowers disappear. Coneflowers, ornamental grasses and other sturdy plants can remain attractive through fall and winter while offering resources for wildlife.

There is another practical reason to become less aggressive with pruning now: Northern Colorado’s first freezes aren’t far away.

Hard cutbacks that stimulate tender new growth are better suited to earlier in the growing season. By September, gardeners generally don’t need to encourage plants to produce a flush of growth that may soon encounter cold temperatures.

A Little Mess Can Be Good

For years, fall garden maintenance often meant cutting plants down, removing every brown stem and leaving beds looking perfectly clean.

A more wildlife-conscious garden can look different.

Allowing selected stems, seed heads and plant material to remain through winter can create habitat while also giving the landscape visual interest during months when flowers are scarce.

That doesn’t mean gardeners have to abandon maintenance. Diseased plant material should be handled appropriately, aggressive self-seeders may warrant deadheading, and particularly messy plants can still be trimmed.

The goal is simply to make the decision plant by plant rather than treating the entire garden the same way.

So, as September settles over Northern Colorado, keep the pruners handy — but don’t feel obligated to use them on everything.

Sometimes a fading flower has finished its summer job.

Sometimes it’s just beginning its winter one.

Source: Adapted from North Forty News’ “Deadheading,” originally written by Bryan Fischer, curator and horticulturist at the Gardens on Spring Creek.