Native to North America, Black-eyed Susans (Rudbeckias or Gloriosa daisies) are a gorgeous addition to any garden or landscape. With their signature bright yellow, orange, red, or purple petals and dark centers, these wildflowers are a haven for pollinators. But have you been wondering how to prune your Black-eyed Susans?
Here are six tips and tricks on how to prune your Black-eyed Susans:
- Cut back your Black-eyed Susans in spring.
- Deadhead spent flowers in summer.
- Prune the entire plant in fall.
- Cut off any diseased plant parts in fall.
- Protect the crown of trimmed flowers before winter.
- Prune crowded Black-eyed Susans before dividing.
In this article, you’ll learn six important ways to keep your Black-eyed Susans healthy and thriving throughout their blooming season. You’ll also get to better understand how to prepare these plants for winter and the next blooming season. So, let’s dive in!
1. Cut Back Your Black-Eyed Susans in Spring
Black-eyed Susans (Rudbeckia hirta) are a gardener’s favorite in many parts of the United States. Whether you have a cottage, vintage, or summer flower garden, these gorgeous plants will add a splash of yellow to golden blooms of upturned flowers with a black seed cone.
Since annual and perennial Black-eyed Susan varieties thrive in the US, it’s essential to know which type will suit your requirements and preferences best.
If you’ve planted a perennial variety, you might have a few stalks left to feed the birds during winter. So, in early spring, you’ll probably have a bunch of old Black-eyed Susans that survived the harsh weather. Your garden will also have a rich supply of new and regenerated Rudbeckias.
You can cut back the old Black-eyed Susans to give room for the fresh and regenerated stalks to thrive as you wait for their blooming season. This clean-up will leave your garden looking neat and more appealing.
Pruning your rudbeckias in spring enables the new stalks to have an extended life. When your Rudbeckias’ stems reach about 12 inches (30 cm) in the middle of their growing season, cut 4 to 6 inches (10-15 cm) of the stems below the flower petal. Cutting back the stalks will enable your plants to become shorter and bushier.
They’ll be healthier and have more vigor to produce more blooms throughout the flowering season. Moreover, if you plan to winterize flower stalks in that growing period, your plants will be full of power and vitality to bear the cold temperatures.
Winterizing some Black-eyed Susans will be a blessing to overwintering birds, including the chickadees, goldfinches, and nuthatches. The plants will also be a perfect shelter for small animals and beneficial insects throughout the winter.
2. Deadhead Spent Flowers in Summer
Your Rudbeckias will start producing blooms in late spring to early summer. In most cases, their flowering season is short-lived, lasting from June to September. But who wouldn’t wish to see beautiful flowers until fall?
You can deadhead your Black-eyed Susans throughout summer to prolong their flowering period. Deadheading is a straightforward plant care routine that involves pinching off or pruning the spent flowers from their base. As a result, it allows the plant to keep attracting pollinators, including butterflies, bees, and birds.
Removing faded or wilted flowers also prevents your Rudbeckias from self-seeding, as these flowering plants are experts at self-sowing. Although some gardeners don’t mind having an upsurge of tiny Black-eyed Susans growing in their gardens, they can create a dull, unappealing sight.
The deadheading technique differs and mainly depends on the plant type.
For flowering ornamental plants, including Black-eyed Susans, roses, and petunias, it’s preferable to cut the base of the stem using sharp gardening tools to encourage the plant to produce more blooms.
For non-flowering ornamental plants such as coleus, it would be best to pinch off the withering foliage to allow the plants to grow healthier leaves.
And with pollinators around, your backyard garden will have plenty of food for months since these beneficial insects and birds will facilitate pollination and fertilization in your plants.
Here’s how to deadhead your Rudbeckias:
Identify Faded or Wilting Flowers
It’s easy to spot faded or wilting Black-eyed Susan flowers since they’re not as bright or attractive as the flesh blooms. Most of their petals will have fallen off, leaving behind the seed cone in the middle.
After identifying the spent flowers, check how many are growing on a single stem.
Cut the Stem
Using sharp, sterilized shears or pruners, cut the stem near the plant’s base if it has produced a single flower per stalk. This will allow your Black-eyed Susan to form new stems and a fresh set of flowers. Ensure that you’ve trimmed the stem approximately ¼ of an inch (0.635 cm) above the topmost leaf.
For Rudbeckias that have produced several blooms on a single stalk, only cut off the wilted flowers. Doing so will allow the stems to form a new set of flowers.
Continue Inspecting for Spent Flowers
Inspect your flowers after a week for spent flowers. It’s best to deadhead your Black-eyed Susans weekly to promote plant growth and blooming. Consistent deadheading will ensure that your garden is always neat and attractive throughout the blooming season.
Note: Deadheading benefits gardeners or flower enthusiasts who love having flowers even fall. For instance, if you’ve planted the Rudbeckia hirta ‘Toto’ variety, your plants will have a new flush of flowers in late fall after the blooming season ends in summer.
3. Prune the Entire Plant in Fall
Apart from deadheading your Black-eyed Susans throughout summer, it’s vital to prune them in the fall season. While some gardeners prefer cutting back their plant before any sign of frost, some wait for the freeze as it makes the stems and leaves softer.
After the first frost, they cut back their Rudbeckias when the remaining flowers start dying due to the temperature changes. Pruning the entire plant during fall encourages it to store sufficient energy in the roots for regeneration in the next growing season.
It’s essential to prune your Black-eyed Susans timely and adequately to avoid damaging the plants. Although they’re hardy, a few mistakes can make you lose your plants to pests or diseases.
Here are some points to note when pruning your Black-eyed Susans during fall:
Avoid Cutting Back to the Roots
Pruning Black-eyed Susans at the end of the flowering season involves cutting back the entire plant. But, don’t trim your plants to the roots. Instead, leave about 2-4 inches (5-10 cm) of the stem above the soil.
Cutting back your Rudbeckias to the soil level (or below) is detrimental, as you might damage the roots. Doing so may expose the roots to the harsh winter weather, lowering the plants’ chances of surviving to the next growing season.
Use Suitable Tools to Prune Your Plants
It’s essential to use proper pruning tools to avoid damaging your Black-eyed Susans. While many gardeners use a wide range of tools to cut back their flowers, it’s best to only use a pair of sterilized pruning shears. This will ensure that you don’t transmit any disease-causing pathogens to your Black-eyed Susans.
Fiskars Pruning Shears (available on Amazon.com) have a bypass blade design, ensuring a clean cut on your flower stems. They also feature a self-cleaning groove to prevent the blade from sticking, not to mention they’ll serve you for years to come since they are rust-resistant and durable.
Alternatively, you can use pruning scissors or a sharp knife to prune your Rudbeckias.
Discard the Trimmed Plant Parts
Dropping the wilted flower parts when deadheading your plants during summer can add some nutrients to the soil. However, avoid doing so after the flowering season. Leaving plant debris in fall will attract pests, which seek shelter in Black-eyed Susans during the cold months.
This can also expose your Black-eyed Susans to diseases.
Leave a Few Unpruned Black-Eyed Susan Plants
Some people opt to leave some Black-eyed Susans untrimmed after the flowering period. Trimming all the plants is preferable to minimize cleaning up your garden in the following growing period. Moreover, Rudbeckias are prolific self-seeders and often become invasive to other plant species.
Nonetheless, you can leave a few unpruned Black-eyed Susans if:
- You want the overwintering birds to feed on the seed cones.
- The plants self-propagate.
- You want to harvest seeds to plant in the next growing season.
To harvest your Black-eyed Susan seeds for propagation:
- Identify spent flowers with a dried, brown center (seed cone) about a month after blooming.
- Put the seed cones in a paper bag and dry them for about a week.
- Break the seed cone of the mature flowers over a hard surface.
- Separate the seeds from the chaff.
- Collect the released seeds, and put them in a seed bag (or envelope).
- Store the seeds in a cool, dry space. Alternatively, chill the seeds in a refrigerator as you await the next growing season to stratify them before planting.
4. Cut off Any Diseased Plant Parts in Fall
For Black-eyed Susans, cutting back the flower stems is the most common form of pruning during the summer and fall seasons. However, it’s also essential to prune other plant parts if exposed to pests or diseases. This gardening practice will prevent the spread of infections and ensure that your plants regenerate with vigor in the following growing season.
Although Black-eyed Susans are generally hardy plants, some growing conditions might expose them to disease-causing pathogens.
The most common pests and diseases that attack the Rudbeckias include:
Fungi
Fungi are the main culprits of health problems in Black-eyed Susans. These organisms cause several fungal diseases that affect these ornamental plants.
These infections include:
| Disease | Causing Fungi | Contributing Factors | Signs or Symptoms |
| Powdery mildew | Erysiphe |
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| Rust | Puccinia, Uromyces, or Aecidium spp. |
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| Leaf spots | Alternaria, Cercospora, Colletotrichum, Phyllosticta, or Septoria spp. |
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| Downy mildew | Plasmopora sp. |
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| Stem rot | Sclerotium rolfsii, or Sclerotinia sclerotiorum |
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| Wilt | Verticillium dahliae |
|
Insects
Apart from beneficial insects, Black-eyed Susans also attract disease-causing bugs. If uncontrolled, these insects can wreak havoc, leading to plant loss.
Bugs that attack Rudbeckias include:
Whiteflies
Whiteflies are moth-like insects that infest the underside of leaves where they lay eggs. They’re common in greenhouse settings, although they can still attack plants in the field.
You can use biological or chemical methods to control whiteflies, including yellow sticky traps, predatory organisms, or insecticidal soaps.
Asiatic Garden Beetles
Asiatic garden beetles attack and feed on the foliage of Rudbeckias at night. But their grubs also feed on the plant roots.
You can control them by using insecticides such as carbaryl or azadirachtin.
Fleahoppers
Nymph and adult fleahoppers feed on the plant sap, damaging the tissues. The female adults also feed on the leaves by puncturing them, resulting in dark or bleached spots.
Using insecticides is the primary method of dealing with these bugs.
Rose Beetles
Rose beetles feed on the leaves at night and hide on their undersides during the day. These insects lay eggs in the soil, and the grubs may feed on their roots after hatching.
Most people control these bugs by handpicking them.
Stalk Borers
Stalk borers attack the inner stalks of most herbaceous plants, causing wilting. However, the larvae also feed on the leaves of neighboring plants.
The best way to control these borers is to remove the affected stalks and eliminate any weeds in your garden.
Spider Mites
Spider mites are insects that attack the undersides of leaves, causing yellowing and withering of the leaves and plants.
Most gardeners use insecticidal soap and horticultural oil to control the bugs.
Phytoplasmas
Black-eyed Susans are also susceptible to attack by bacteria-like organisms called phytoplasmas. These microorganisms attack the plant’s vascular tissues (phloem), causing aster yellow disease.
The symptoms of this infection include:
- Yellowing
- Dwarfism
- Leaf-like structures replacing flowers
- Abnormal branching
5. Protect the Crown of Trimmed Flowers Before Winter
Since most gardeners prefer tidying up their Rudbeckia gardens in fall (to save them from doing so in spring), they opt to shave off all their plants a few inches (5+ cm) above soil level. However, the temperatures in the fall and winter seasons might fall to extreme levels for you to safely follow this practice.
And although perennial Black-eyed Susans can withstand the harsh winter weather, the trimmed stems might suffer from being exposed to the freezing temperatures. The roots can also lose some of their stored energy, which would have been beneficial in rejuvenating the plants in spring.
That’s why it’s best to insulate your soil to protect the roots and the stems from the harsh weather. You can do so by covering the crown of the trimmed flowers with about 2 to 4 inches (5-10 cm) of mulch. It would be preferable to spread the mulch after a few touches of frost have occurred (about three to four).
You should also ensure that you remove all diseased plants when cutting back your Black-eyed Susans during fall to prevent disease transmission.
Mulching will ensure that the soil’s temperature is slightly higher than the air’s. The cover enables your plants to survive through the winter season. Don’t forget to remove the mulch in early spring once the weather starts warming up.
6. Prune Crowded Black-Eyed Susans Before Dividing
Since Black-eyed Susans are excellent self-propagators, it’s not uncommon for them to thrive and become overcrowded. Overcrowding is detrimental to your plants as it limits their blooming capabilities. The roots will begin to compete for nutrients and water in the soil.
For this reason, dividing your Rudbeckias after a couple of years (3 to 5) is a good gardening practice. Dividing your plants is best during early spring, as it improves air circulation during the growing period.
However, some gardeners prefer conducting this practice in the fall season. Farmers who divide their Rudbeckias in fall identify bigger plants at the end of the growing season.
The foliage of some mature Rudbeckias will have started wilting by then. Therefore, choosing which plants to transplant and which to leave behind is generally easier.
Preparing the plant and the transplanting site is preferable before dividing your plants. It’s best to prune the foliage first to determine the best section to divide.
You can:
- Cut back the foliage up to about 6 inches (15 cm) above the soil.
- Dig around the plant using a sharp shovel to expose the roots.
- Cut the edges and dig deeper.
- Lift the plant.
- Flip the roots and divide them into equal segments.
- Transplant and water the divided plants.
Final Thoughts
Black-eyed Susans are attractive herbaceous plants that comprise annual and perennial varieties. Nonetheless, they have a short blooming season.
Therefore, it’s essential to prune them to ensure that they’re healthy and experience an extended flowering season.
Here are some pruning tips to make your Rudbeckias maintain their bloom for longer:
- Cut back your Black-eyed Susans in spring.
- Deadhead your Black-eyed Susans in summer.
- Prune your Black-eyed Susans in the fall.
- Cut off any diseased plant parts in the fall.
- Protect the crown of trimmed flowers before winter.
- Prune crowded Black-eyed Susans before dividing.
