A North America native, rudbeckias or black-eyed Susans have been grown by indigenous tribes for centuries. Ancient people used the plant for washing off sores and swellings and treating snake bites and childhood colds.
After Columbus landed in the Americas, rudbeckia caught the attention of Europeans, and they quickly caught on in Europe. In 1918, these daisy-like blooms became the floral emblem of Maryland. The language of flowers lists rudbeckias as symbols of justice, and with more than two dozen wild species, gardeners have many varieties to choose from.
Rubeckia grows equally well indoors and out. Fertile soil is key to successful growth, so look for a moist, well-draining location that can tolerate tough conditions. Soil should reach a temperature of 70°F, which makes the months of March through May the ideal planting period. Germination takes just one to three weeks, so you'll notice beautiful blossoms in no time.
Rudbeckia can reach over three feet in height, so be cautious when growing plants indoors. Leaves can extend beyond six inches, with flowers two to three inches in diameter. Once they start blooming, plants will spread between 12 and 18 inches, so keep this in mind if you're growing multiples. Certain varieties spread further than others.
Proper spacing significantly impacts results; it boosts air circulation, keeps leaves dry, and helps prevent disease from spreading.
These wildflowers are major sun lovers, so keep them in full sun throughout their growth cycle. While rudbeckias are hardy plants that can handle partial sunlight, they'll grow bigger and brighter when they have at least six hours of direct sunlight each day. If you're growing your flowers indoors, keep them near the brightest window.
While rudbeckia is a drought-tolerant plant, always prevent the soil from becoming bone dry. Your plants need sufficient water to produce healthy roots, so aim for about one inch weekly. This provides just enough to soak into the roots; you'll know to water when the top of the soil feels dry.
If conditions are sandy or you're experiencing excessive heat, boost watering by an inch or so until the top layer of soil stays sufficiently moist.
Rudbeckia is susceptible to several predators, including aphids, caterpillars, Japanese beetles, and two-spotted spider mites. Each of these can chew away at roots, stems, leaves, and blossoms, destroying your entire crop.
Insecticidal soaps, sprays, and horticultural oil are effective at removing most pests. Mammals such as raccoons and skunks eat larvae left behind by pesky intruders, while predatory mites feed on spider mites. Additionally, look for products containing Bt and Bacillus papillae to help keep pest populations down.
Rudbeckia can fall prey to several common diseases, including bacterial leaf spots, fungal leaf spots, downy mildew, and fungal rot. If you notice discoloration, holes, or spores on your plants, take action immediately.
The presence of these devastating pathogens is boosted by excess leaf moisture, so proper spacing and removing dead plant material can work wonders. Eliminate as much moisture and humidity around plants as possible. Irrigation is another cause of excess wetness, so use drip irrigation to reduce risk. Apply fungicide early and often to combat fungal diseases, and get rid of any affected plants promptly.
Your rudbeckia plants require several nutrients to reach peak growth. Use bone meal to increase the calcium content in your soil; this necessary ingredient offers structural support to cells and boosts strength when plants are stressed.
Conduct a soil test to determine phosphorus levels. Many gardens will require a phosphorus-rich fertilizer, but if you reside in an area with naturally high phosphorus content, it's not needed. A slow-release fertilizer can be spread at a rate of one pound for every 100 feet once new leaves start growing. Add a 1/2 pound midway through the growing season.
Propagating rudbeckia through cuttings is quite simple. Each spring, take cuttings from healthy plants; they should be about four to six inches each. Cut from below the parent plant's leaf node, and root the cuttings in small containers. Once roots start sprouting, it's time to move your cuttings outdoors to a sunny spot.
An excellent addition to any garden, rudbeckia attracts a host of pollinators. The sweet nectar and bright color bring in butterflies, bees, hoverflies, and beetles. The open faces of your flowers are easy to spot, so expect plenty of action all season. Rudbeckia also stands out among other species; the blooms look beautiful next to bold blue and purple flowers.
Rudbeckia comes in an assortment of colors and sizes.