Cutting back of dead or dying top growth is the only maintenance that is needed for winter preparation. Cut the stems down to the ground, or to the basal growth if you are gardening in the warmer hardiness zones. Alternatively, the flower stems can be left to cut back in the spring.
Black-Eyed Susan foliage and flower stems will die back completely to the ground, starting in September in some parts of the country. Cutting back the spent growth will help to prevent any diseases from spreading or pests that may affect your plant.
Because of this, you may want to hold off on cutting Black-eyed Susans back. "They can be deadheaded any time of year to promote new flower growth, but pruning the entire plant should be done autumn to early spring," McDonough says.
Black Eyed Susans: End of Season Care
Overwintering: Cut remaining stalks to the ground in either fall or spring. Dividing & Transplanting: True perennial types, especially Rudbeckia 'Goldstrum' will benefit from dividing every three to five years. Leave any varieties designated as 'short-lived perennial' undisturbed.
For Rudbeckias with multiple flowers on a stem, just snip off the spent blooms. In autumn, cut Black-Eyed Susan back to about 4 inches tall (10 cm.) or, if you wouldn't mind a few more Black-Eyed Susan plants, let the last blooms go to seed for the birds.
About Black-Eyed Susan
Snipping spent blooms in fall prevents self-seeding. But if you leave faded flowers in place, they'll add winter interest to the landscape and attract seed-eating birds.
Transplanting Black-Eyed Susan
Dig up a clump and break off chunks of plantlets. Make sure to keep as many roots attached as possible. Replant the new clumps at the same depth they were growing. Water the area well and let the water fully absorb.
If you don't cut down the seed heads, annual black-eyed Susans will reseed themselves and pop up in delightfully unexpected spots next year.
You can propagate perennial black-eyed Susans by division in early spring, just as growth begins to develop, or in the fall after they finish flowering. Simply dig up the root ball and cut it with a sharp knife, making sure each division has roots. Replant the divisions about 12 to 18 inches apart.
Expert Response. Black eyed Susan, Rudbeckia hirta will topple over if they become too lush from heavy rainfall or too much fertilization.
Common Reasons Why Black-Eyed Susan Isn't Blooming
Not deadheading Black-Eyed Susans regularly will slow down blooming. The plant will put energy into producing seed instead of more flower production. Keep your plant deadheaded all summer to prolong the blooming period.
Not Deadheading Enough
As previously mentioned, Black-Eyed Susans can have a very long season if planted early enough. However, plan to deadhead several times throughout the year to prolong the season even more and ensure your plants don't go to seed too early.
For the best black-eyed Susan care, don't overfertilize. Overfertilization causes the flower stems to droop or become weak. If you're going to fertilize at all, use a general-purpose slow-release granular fertilizer with a 12-6-6 NPK sparingly once or twice a year.
It usually grows as a biennial, which means it takes two years to bloom from seed. Biennials live only two years, and bloom only their second season, then die after reseeding heavily.
Some people just scatter them and leave them uncovered. Plant them in a fertile soil (we usually use an all purpose organic feed and a good compost to fortify our bed). You can definitely start black-eyed Susans by seed indoors.
Black-eyed Susans will bloom longer if you deadhead them, which means cutting off spent, faded, or dried up flowers once they're past their prime. Always cut the stem back to just beyond a leaf so you don't leave dead, dried-up stems poking out.
Instructions. Plant black-eyed Susans when the soil temperature is around 70⁰ F for best seed germination. Sow by seed in loosely covered soil. This plant tends to spread out, so plant the seeds closer together to prevent them from sprawling (if you'd like).
Planting fresh seed each season will guarantee a new crop. Other varieties, like the familiar roadside Black-eyed Susans (Rudbeckia hirta), are actually biennial in the wild (meaning they germinate in the spring but only flower in their second year).
Black-Eyed Susans will bloom profusely between June and October. They will bloom more frequently if their spent flowers are removed. One warning is that this flower can become invasive into the rest of your garden! Be sure to give them plenty of space to grow as they will crowd out other flowers.
If they bloom in the spring, divide and transplant them in the fall. However, black-eyed Susans are very hardy perennials that stand up well to the stress of being relocated. As a result, the best time to transplant them is when they are dormant (early spring or fall), well before the first frost.
Mulch around the base and root area of Black-Eyed Susan to improve the soil texture and moisture retention over time. Using organic compost will also supply the nutrients needed to support healthy growth for the whole season.
How to Plant Black-eyed Susan. Plants should be set 18 inches apart. Remove weeds and loosen the soil. Make a hole a few inches wider than the plant and set in the hole; backfill with soil, tamp gently, and water well.
Cut them back to 2 inches above the ground at the end of the season. Add mulch during cold months to keep them from freezing before spring. Black-eyed Susan propagates from underground rhizomes and self-seeds, so if you want to keep them from becoming invasive, clean up seed pods and trim back growth.
The Short Answer. Yes. According to sources like the Missouri Botanical Garden and University of Nebraska Extension, black-eyed susans (also known as Rudbeckia species) are plants that can be moderately to heavily damaged by rabbit feeding.