12 Flowers You Should Never Deadhead in September

As summer slowly fades into fall, gardeners everywhere start to notice the subtle changes in their gardens.

The days grow shorter, the nights cooler, and the flowers that once burst with color begin to take on a different role.

For many, the instinct to tidy up the garden by deadheading spent flowers becomes almost second nature.

But before you reach for those pruning shears, it’s essential to know that not every flower benefits from being deadheaded in September.

Some flowers, in fact, rely on their fading blooms to complete their life cycle, prepare for winter, or even reseed for the next growing season.

Through years of experience and a few hard-learned lessons, I’ve discovered which flowers should be left alone as autumn approaches.

Here are 12 flowers you should never deadhead in September.

1. Black-Eyed Susan (Rudbeckia)

Black-Eyed Susans are a staple in many gardens, with their bright yellow petals and dark centers that bring cheer to any landscape.

However, as tempting as it might be to snip off those fading blooms, it’s best to resist in September.

The spent flowers of Black-Eyed Susans produce seeds that provide a critical food source for birds during the colder months.

I learned this lesson a few years ago when I deadheaded my Black-Eyed Susans in early September, thinking I was keeping the garden neat.

But instead of benefiting from tidy flower beds, I missed out on the flurry of bird activity that usually graces my garden in late fall.

Let those blooms dry and set seed; the birds will thank you for it.

2. Coneflower (Echinacea)

Coneflowers are another garden favorite, known for their hardiness and long-lasting blooms.

But when it comes to deadheading in September, these flowers should be left alone.

Like Black-Eyed Susans, coneflowers produce seeds that attract birds, particularly goldfinches, who rely on them for food.

I once made the mistake of deadheading my coneflowers in September, not realizing that the dried seed heads were a buffet for local birds.

I quickly regretted it when my garden became noticeably quieter, missing the cheerful chirping of finches.

Now, I let the coneflowers stand tall, enjoying their dried beauty and the wildlife they attract.

3. Sedum (Stonecrop)

Sedums are known for their succulent leaves and clusters of star-shaped flowers that bloom late into the season.

As September rolls around, these flowers begin to fade, but they shouldn’t be deadheaded just yet.

Sedum flowers turn into attractive seed heads that add winter interest to the garden and provide food for birds.

One fall, I pruned back my sedums too early, and I was left with bare spots in the garden during winter when I could have enjoyed their unique seed heads dusted with snow.

Now, I leave them be, appreciating their structure and the way they bring life to my garden even in the coldest months.

4. Joe Pye Weed (Eutrochium purpureum)

Joe Pye Weed is a tall, striking plant with clusters of purple flowers that bloom late in the summer.

This plant is a magnet for butterflies and bees, and its seed heads can be equally valuable for birds.

Deadheading Joe Pye Weed in September can rob your garden of these benefits.

I used to cut back the spent blooms as soon as they started to fade, but after reading about their value to wildlife, I decided to let them be one year.

The result was a garden filled with birds enjoying the seeds, and I’ve never looked back since.

Letting Joe Pye Weed go to seed not only helps wildlife but also adds a natural, wild beauty to the fall and winter garden.

5. Goldenrod (Solidago)

Goldenrod is often associated with late summer and early fall, with its bright yellow plumes lighting up the garden.

While some gardeners might be tempted to deadhead Goldenrod to tidy up, doing so in September can be a mistake.

Goldenrod is another plant that produces seeds that are valuable for birds as they prepare for winter.

I remember one September when I cut back all my Goldenrod, thinking I was getting ahead on my fall cleanup.

But I soon realized that I had taken away an essential food source for the finches and sparrows that usually frequent my garden.

Now, I leave the Goldenrod to set seed, and my garden remains alive with activity well into the fall.

6. Asters

Asters are quintessential fall flowers, known for their vibrant colors and late-season blooms.

As September progresses, asters begin to fade, but they should not be deadheaded during this time.

The seeds that develop after the blooms fade are crucial for many bird species, especially those preparing for migration.

A few years ago, I pruned back my asters in early September, wanting to keep the garden looking tidy.

But instead of a neat garden, I ended up with fewer birds visiting, and I missed out on watching them feast on the seeds.

Now, I let my asters go to seed, and my garden is a haven for birds as the season winds down.

7. Sunflowers (Helianthus)

Sunflowers are the epitome of summer, but as the season shifts to fall, these towering plants begin to fade.

However, deadheading sunflowers in September would be a missed opportunity.

Sunflower seeds are a favorite among many bird species, including chickadees, cardinals, and even woodpeckers.

I remember one year when I cut down my sunflowers too early, thinking I would save myself some work later on.

But instead of reaping the benefits of having birds in my garden, I noticed a significant drop in their visits.

Now, I leave the sunflower heads standing, enjoying the sight of birds perched on them, eagerly picking at the seeds.

8. Milkweed (Asclepias)

Milkweed is best known as the host plant for monarch butterflies, but its role in the garden doesn’t end when the flowers fade.

Milkweed produces fluffy seed pods that are important for the plant’s life cycle and also add interest to the fall and winter garden.

Deadheading milkweed in September can prevent these seeds from maturing and dispersing naturally, which is essential for supporting future generations of butterflies.

I once deadheaded my milkweed in late summer, not realizing that I was cutting off potential seeds that could have helped more monarchs the following year.

Since then, I’ve let the seed pods form and disperse naturally, and my garden has become a haven for monarchs and other pollinators.

9. Marigolds (Tagetes)

Marigolds are often associated with summer gardens, but as September comes around, they begin to wind down.

While deadheading marigolds throughout the growing season can encourage more blooms, September is the time to let them be.

Allowing marigolds to go to seed in September can help them reseed themselves for the following year, especially in warmer climates.

I used to deadhead my marigolds religiously, but after noticing that some had naturally reseeded in my garden one year, I decided to leave them alone in September.

The result was a more abundant and vibrant display of marigolds the next year, with minimal effort on my part.

10. Rudbeckia

Rudbeckia, also known as Black-Eyed Susan, is a resilient flower that brightens up the garden with its golden-yellow blooms.

As September approaches, these flowers start to fade, but deadheading them now would be a mistake.

Rudbeckia produces seeds that are a valuable food source for birds, particularly finches.

One autumn, I decided to deadhead my Rudbeckia early, hoping to keep the garden looking neat.

But I quickly realized my mistake when the usual flocks of finches that visit my garden were nowhere to be seen.

Now, I let the Rudbeckia go to seed, and I’m rewarded with the sight of birds flocking to my garden as fall deepens.

11. Cosmos

Cosmos are delicate, airy flowers that bring a sense of whimsy to any garden.

They bloom profusely in the summer, and by September, they start to fade.

However, deadheading cosmos in September can prevent them from reseeding naturally.

Cosmos are known for their ability to self-sow, and leaving the spent flowers in place can result in a fresh crop of blooms the following year.

I used to deadhead my cosmos regularly, but after learning about their reseeding capabilities, I decided to let them be in September.

The next year, I was delighted to find new cosmos plants popping up throughout the garden, creating a beautiful, effortless display.

12. Yarrow (Achillea)

Yarrow is a hardy perennial that produces clusters of tiny flowers throughout the summer.

As September arrives, the flowers begin to fade, but this is not the time to deadhead.

Yarrow produces seeds that can help the plant spread and establish new clumps in the garden.

I once deadheaded my yarrow too early, and I noticed that it didn’t spread as much the following year.

Since then, I’ve let the flowers go to seed, and I’ve been rewarded with more robust clumps of yarrow that fill in the garden beautifully.

Final Thoughts

Deadheading is an essential part of garden maintenance, but timing is everything.

While it can be tempting to tidy up the garden as summer gives way to fall, it’s important to consider the role that spent flowers play in the ecosystem.

Many flowers provide valuable food sources for birds, help plants reseed, or add winter interest to the garden when left alone.

Through my own experiences, I’ve learned that leaving certain flowers unpruned in September can bring unexpected benefits, from attracting wildlife to ensuring a more vibrant garden the following year.

So, as you stroll through your garden this September, take a moment to consider the future and the natural cycles at play.

By letting some flowers go to seed, you’re not only supporting your garden’s health but also contributing to a thriving ecosystem.

Happy gardening!