Are Black-Eyed Susans Annual, Biennial, or Perennial Flowers?
Black eyed susans are a favorite flower amongst many gardeners all over the world. But if you plant them once, will they come back? In this article, we take a deeper look at rudbeckia, and whether it's considered an annual, biennial, or perennial flowering plant based on the hardiness zone you are growing in.
Many gardeners choose to plant flowers in their gardens with different life cycles. This provides ideal visual impact, as well as offers flexibility in the garden. If you’ve decided to grow Black-Eyed Susans in your garden, these plants are known for their pop of color, ability to reseed, and how low maintenance they are.
Black-Eyed Susans are beautiful plants that bloom into vibrant flowers. Although they are wildflowers, gardeners love to cultivate them at home. The various colors and lifecycles make these flowers the perfect addition to any garden.
These cheery flowers are also beloved because there are multiple varieties with differences in how they can be grown. Below, we will discuss the differences between these varieties and which are considered annual, biennial, or perennial flowering plants. Ready to learn more? Let’s dig in!
The Short Answer
Black-Eyed Susans are a part of the plant genus Rudbeckia. This genus contains perennial, biennial and annual varieties. This means that technically, they can be all three. It also means that there are plenty of options when choosing these flowers for your garden. All varieties can be treated as annuals that need replanted each year. But if you live in hardiness zone 3-9, some varieties will come back each season.
The Long Answer
Gardening can monopolize a great deal of time. Many people love to devote hours to growing their plants, but others don’t have much extra time. It helps to understand what classification a plant falls into before dedicating time to maintain them. Let’s look at the difference between annuals, biennials, and perennials.
Annual flowering plants are those that will die off in extreme heat, or during winter frost. They are planted each year, and called “annuals” for short. Often, those who spend more time in the garden prefer annuals, because they can be planted for just one season. The quick turnover allows gardeners to choose new plants year after year if they so choose.
Biennials fall somewhere in between annuals and perennials. Their life cycle typically lasts two growing seasons. Luckily for gardeners, different varieties of Black-Eyed Susans fall into each category.
On the other hand, flowering perennials are perfect for gardeners with little time on their hands. These grow back year after year for more than two years. This requires less maintenance while still providing beautiful, healthy plants.
What Category Do They Fall Into?
Black-Eyed Susans are native to the eastern United States, making them one of the unique plants that can survive harsh winters. This makes them ideal for gardeners in the northern United States. They come in different varieties that can be any of the three classifications. There are annual varieties, biennial varieties, or perennial varieties.
Some varieties can survive temperatures as low as -40°F. This means in most growing climates, they can be considered perennial flowering plants.
However, certain species can only handle temperatures as low as 30°F. Perennial varieties have strong roots that can carry them through these harsh winters.
Similarly, they can tolerate suboptimal soil. The main environmental conditions that impact growth are the amount of sunlight and the drainage ability of the soil. Plus, plants that are planted in pots will struggle to stand up to harsh winters without a bit of insulation.
Black-Eyed Susans can grow mostly in USDA hardiness zones 3 through 9, and rarely in zone 10. They bloom in radiant yellow from June to September and do best in mild climates.
With proper care, there are some varieties that can grow just about anywhere the temperature doesn’t drop below -40°F, though most prefer to keep above -20°F.
The extreme cold hardiness zones of 1-3 and the warmer zones of 10-13 cannot provide a good home for these popular flowers. Zones 1-3 are mostly the upper parts of frigid Alaska and the central northern states such as Montana, Minnestoa, and North Dakota.
Zones 10-13 include the southernmost part of Florida, Puerto Rico, and bits of Hawaii. The temperatures in these areas are simply too extreme for them to live.
Black-Eyes Susan Varieties
When you hear the name Black-Eyed Susan, thoughts of a daisy-like flower with bright yellow petals and a black center may appear. However, there are 12 variations of the flower, and each variety can differ in color, size, and life cycle.
Biennials or Short-Lived Perennials
Nine of the 12 varieties are Rudbeckia hirta. There are three Rudbeckia hirta varieties that can be biennials or short-lived perennials:
- Rudbeckia hirta, ‘Indian Summer’: Hardiness zones 3-7
- Rudbeckia hirta, ‘Moreno’: Hardiness zones 3-8
- Rudbeckia hirta, ‘Cherokee Sunset’: zones 5-9
Although the flowers of the ‘Cherokee Sunset’ can be grown as biennials or short-lived perennials, they are usually grown as annuals instead.
There are four varieties of Rudbeckia hirta that are short-lived perennials but can be treated as annuals.
- Rudbeckia hirta, ‘Toto Rustic’: Hardiness zones 5-10
- Rudbeckia hirta, ‘Prairie Sun’: Hardiness zones 5-9
- Rudbeckia hirta, ‘Irish Eyes’: Hardiness zones 5-9
- Rudbeckia hirta, ‘Cappaccino’: Hardiness zones 5-9
- Rudbeckia hirta, ‘Maya’: Hardiness zones 4-9
- Rudbeckia hirta, ‘Cherry Brandy’: Hardiness zones 5-9
Rudbeckia hirta ‘Maya’, can be annual or biennial. The ‘Cherry Brandy’ is most reliable as an annual or biennial.
This leaves us with three varieties. All of the following flowers are grown as perennials:
- Rudbeckia fulgida, ‘Goldstrum’: zones 3-9
- Rudbeckia laciniata, ‘Cut-Leaf Coneflower’: zones 3-9
- Rudbeckia subtomentosa, ‘Henry Eilers’: zones 4-8
Other Environmental Factors
Though they can grow in different hardiness zones, all varieties prefer full sunshine. Ideally, they should receive six hours of direct sunlight daily, but they can grow under partial sunlight. Unfortunately, it will be more difficult for the plants to flower under partial sun.
They can stand up to varying soil conditions. Although fertile soil is best, these plants can tolerate less-than-ideal soil situations. The most essential factor is that the soil is well-draining.
For those who choose to grow their Black-Eyed Susans in pots, choose at least a one-gallon pot to provide plenty of space for blooming. If you have placed your plants in an area that receives full sun, water them daily.
Also, potted plants are less protected from harsh winters than those planted in the ground. You can protect them by placing leaves or blankets around the pot if you live in zones three to five.
Growing Black-Eyed Susans
The basics of growing Black-Eyed Susans will remain the same, regardless of the lifecycle of any one variety. In most of North America, it is best to plant your seeds between March and May.
First, you must decide whether you plan to plant your seeds inside or outside. If you are growing them inside, begin planting six to ten weeks before the last frost of the season. If you are planting them outside, remember that the soil must be able to drain easily. It should be between 70 to 75°F.
Be sure to cover the seeds with only a small amount of soil because they will need plenty of sunlight to germinate.
Plant them close together if you hope to prevent them from spreading. They may spread across 12 to 18 inches if you are not careful. However, planting them further apart can create a full border and prevent disease.
You can skip these steps if you want to purchase transplants from a nursery.
As your flowers grow, remove dead flowers and plant debris to cut down on self-sowing. Instead, prune the plant after its flowers. This may allow them to bloom again in the late fall. As fall approaches, stop removing so many seed heads. A few of these will attract birds.
Once you enter the second season, you won’t need to put in as much work. At that point, your plants will be ready to reseed themselves.
Throughout the growth cycle, watering can be tricky. When the weather is dry, water every week. Be careful not to overwater, or your flowers may become diseased. Likewise, overhead sprinklers can cause disease. Instead, use drip systems or soaker hoses.
Growing as Perennials
Most varieties should or can be grown as perennials. Perennials should be planted eight to ten weeks before the final frost of the season.
As perennials, they will return every year if properly cared for. Overall, they cost less money over time because you only have to purchase the plants once every few years.
It is important to divide perennial types every 3-4 years. You will have to remove dead flowers and plant debris frequently to prevent more plants from growing each year and crowding the existing plants. This keeps the plants healthy
Their roots are strong enough to stand up to the winter cold. However, an especially cold winter can ruin your plans of having your plants regrow every year.
Growing as Biennials
Biennials will need to be maintained for one season just like perennial flowers. Avoid removing dead flowers and debris, and the seeds that they drop will regrow in the same spot as the existing plants. Once the first set of flowers dies, the next will already be growing.
On the other hand, you can remove the dead flowers and debris, and your plants will still complete their lifecycles within two years.
Growing as Annuals
If they are grown as annuals, you should plant them indoors close to six weeks before your last spring frost. They will bloom 100 days after the transplant date.
There are a number of reasons you may choose annual varieties for these reasons. For instance, they bloom more quickly than perennials. Also, the start-up cost is lower because annual plants are cheaper than perennials.
There are a few downsides to growing Black-Eyed Susans as Annuals. One example is that by the end of the lifecycle, they will drop more seeds that they can regrow the following season.
Most Black-Eyed Susans are perennials, but some are biennials or annuals. Some varieties can even be treated as either of two options. This versatility is one of the many factors that attract gardeners.
When deciding which variety to plant, consider your gardening skills, available funds, and amount of free time. Regardless of your selection, you are sure to be pleased by the beauty of these stunning wildflowers!