Black-Eyed Susan: Everything You Need To Know Before Planting

Black-eyed Susans are delightfully bright wildflowers that can be seen gracing gardens, fields, and roadways throughout most of the United States and the southern parts of Canada. Hardy in temperature zones three through nine, these happy flowers have a dark center surrounded by a petal arrangement similar to daises, and they grow just about anywhere. 

Botanically speaking, black-eyed Susans are members of the Asteraceae family and are known specifically as Rudbeckia hirta. Per the Farmer's Almanac, they grow to be around 3 feet tall with 6-inch-long leaves. Bloom size ranges from 2 to 3 inches in diameter. One of their common nicknames is the Gloriosa daisy, and you can find them blossoming from late spring until the very end of summer. Plant these beauties in your garden and for months on end, you'll enjoy a dazzling display of color that will attract both butterflies and bees.

According to the Prince William Conservation Alliance, black-eyed Susans also have the lesser-known nickname of pioneer plant. This alludes to their diehard resilience and the fact that they will generally be the first flower to pop up in any newly cleared fields or woodland areas. More often than not, they are biennial, meaning blooms will not appear until two years after seeding.

Sure, you can just head down to the local garden center and buy black-eyed Susan seedlings or fully grown plants ready to transplant into your yard, but why not try your hand at growing them from seed? In their comprehensive grow and care guide, the DIYers at Growit Buildit have laid out a handy step-by-step guide. It may seem daunting at first glance, but that's only because it is thorough. Black-eyed Susans are easy to grow and with a few essential supplies, you should have no trouble at all.

Early spring is the time to get things started by gathering your seed trays, a garden trowel, a spray bottle, and seeds, which can be purchased online or at a nursery. For your potting soil, always choose a high-quality mix to give the seeds the best chance at sprouting, and pre-moisten it before planting. Fill each tray almost to the top, but not quite. Each cell can get up to five seeds, which you will cover with more soil. After that, you can spread any remaining seeds over the top of the soil. It's fine for them to stay exposed. Next, spritz each individual tray cell with your spray bottle filled with water. You'll want the trays to live somewhere that will get plenty of early sun. Make sure the soil stays moist and look for seedlings to shoot up after about two weeks.

Black-eyed Susans can grow quite tall, and because they only have flowers at the very top of each stem, it's easy for them to become top-heavy. This leaves them at the mercy of strong winds or a thorough downpour of rain, which could knock them over and cause serious damage. To prevent your towering blossoms from bending and potentially snapping their stems, MSU Extension recommends staking them as they get taller or growing them from seedlings along with supplemental support like an obelisk.

Lowe's concurs that earlier is better, noting that if you stake them too late in the year, you risk hurting the underground root system when you drive the stake down (via YouTube). Doing so in the springtime is a better option because the roots will be much smaller and more contained. Regardless of when you get around to staking, Lowe's says to be sure the stake is inserted a few inches away from the base of the stems. Then gently and loosely tie those stems somewhere around the middle of each stalk. If you have a particularly wide patch of black-eyed Susans, you might want to consider installing a fence line to prop them up. As the plants flush out, any initially viewable fence support will become hidden by the foliage.

Black-eyed Susans are similar in structure to purple coneflowers, but they each belong to different genera. Laidback Gardener explains that it used to be easy to tell the two apart by color alone. One was yellow (Rudbeckia hirta) and one was pinkish-purple (Echinacea purpurea). Since recent hybrids now come in a rainbow of colors, that distinction is harder to spot. Still, the primary differences between the two lie in their center cones. Rudbeckia cones are darker and soft to the touch, while Echinacea cones are never black and are made up of tiny spikes called paleae. Echinacea is known around the world for its medicinal properties, but black-eyed Susans are only grown for ornamental purposes. In fact, black-eyed Susans are not considered safe to eat, so it's important that you can spot the differences and properly identify your plants. To make things even more confusing, there is a hybrid called × Echibeckia, which brings the two together into one species.

Here are some other varieties of Rudbeckia, the original black-eyed Susan:

• Rudbeckia hirta cappuccino, seen pictured above, was a winner of the Royal Horticultural Society's Award of Garden Merit.
• Prairie Sun Rudbeckia stands out because of its unusual light green center cone.
• Cherry Brandy Rudbeckia is a stunner with a warm brown cone and dual-toned petals that start deep crimson at the center and flush out into a lighter cherry red.
• Little Goldstar Rudbeckia is a shorter, bushier variety that can boast up to 80 blooms per plant.

For container gardeners, repotting your black-eyed Susan plants is an absolute necessity. They reproduce on their own by dropping their seeds wherever they grow, and they also expand under the soil by continually spreading their rhizomes. These root systems are dense and will keep growing to fill up whatever space they are offered. This means that they have the potential to become invasive when planted directly into the ground. Container growing will require sturdy pots and regular rhizome division with each repotting.

When you're ready to repot your plant, you'll first need to dig up the entire rhizome and break it into smaller pieces. Due to their propensity for spreading, Epic Gardening advises upgrading to significantly bigger pots each time. The small pieces of rhizome should be planted in well-draining potting soil with a high organic matter content. Try to make the new environment similar to the old by burying the rhizome pieces to the same depth as the original plant. Backfill with additional soil and your new black-eyed Susans will be ready to go.

There are a few common pest issues and diseases to look out for with black-eyed Susans. The Connecticut Agriculture Experiment Station (CAES) lists among them downy and powdery mildew, which are two different concerns, leaf spots from bacteria such as Septoria, and rust. Downy mildew is likely to appear when the climate remains cold and wet for a period of time. Powdery mildew is more common when humidity is high but it hasn't been raining. Fungicides may be employed for each of these conditions, as well as for leaf spots and rust. However, CAES makes it clear that different formulations are permitted in different states. Always consult local professionals for guidance before applying fungicides.

On a different note, black-eyed Susan plants suffering from overall yellowing may have a disease called aster yellows. In such incidences, CAES recommends removing and destroying them to prevent further infections.

Regarding insects and pests, CAES points to several offenders, including Asiatic garden beetles, crescentmarked lily aphids, sawflies, stalk borers, and twospotted spider mites. This may seem like a long list, but it doesn't mean all these insects will show up in your yard and destroy your flowers. North Carolina State Extension Gardener reminds us that, for the most part, black-eyed Susans tend to remain untouched by pests. If you find yourself with a beetle or stalk borer problem, it's best to consult your local nursery. Aphids and spider mites can usually be taken care of with insecticidal soaps and neem oil, per Secure Lawn. Both of these products should be available for purchase at any home and garden center.