Transplanting black eyed susans

Transplanting Black-eyed Susans

Question:

When is a good time to transplant Black-eyed Susans?

Hardiness Zone: 6a

Peggy from Chillicothe, OH

Answer:

A good rule of thumb to follow for transplanting perennials is if they bloom in the fall, divide and transplant them in the spring. If they bloom in the spring, divide and transplant them in the fall.

Black-eyed Susans are one example of a perennial that stands up well to the stress of being relocated. Technically speaking, the best time to transplant them is when they are dormant (early spring or fall). This will cause them the least amount of stress.

Planting them in the fall has its advantages, because it gives their roots time to become established before winter sets in, which will get them off to a faster start in the spring. Not-so-technically speaking, you can probably transplant Black-eyed Susans almost anytime as long as you do it during the coolest part of the day and give them plenty to drink. They may not bloom the first year after you transplant them, but they always seem to come around eventually.

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Ellen

By Julie Christensen

Black-eyed Susans (Rudbeckia hirta), also known as coneflowers or Gloriosa daisies, make up a family of about 30 species of flowers, all native to North America. These plants grow wild in woodland areas and fields, and tolerate a wide variety of growing conditions. They’re prized in the garden for their bright yellow-orange, daisy-like flowers with the characteristic brown or black middle. The flowers also make fine cutting flowers and attract butterflies and birds to the garden.

Black-eyed Susans are short-lived perennials, annuals or biennials, depending on the climate and variety. Perennial varieties are usually hardy in U.S.D.A. plant hardiness zones 4 through 7. When left to their own devices, the plants self-sow prolifically, and will likely return even if they grow as annuals in your area.

Getting Started

Black-eyed Susans are usually started as nursery transplants, but you can also grow them from seed. The seeds need a period of moist cold, known as stratification, to break dormancy and germinate. To achieve this, you can either sow them outdoors in the fall or store them indoors in a refrigerator. If storing indoors, place the seeds in a baggie with 1 tablespoon of moistened potting mix and put them in the refrigerator for 12 weeks prior to sowing. Sow seeds indoors 8 weeks before the last expected frost. Place seeds in a light starting mix and cover them with 1/16 inch of soil. Keep the soil slightly moist and warm. Seeds germinate in 12 to 30 days at 70 degrees Fahrenheit.

If you’d like to save seeds, allow the heads to ripen from green to brown or black. Inside these heads lie thousands of seeds. Leave the heads intact on the plants for several weeks after the flowers fade, or until the heads darken and start to fall apart. Cut the heads off and break them open. Shake out the seeds onto a cookie tray and allow them to dry out thoroughly for several weeks. Place the seeds in a labeled bag and store them in the refrigerator or plant them directly in the garden in the fall.

Plant black-eyed Susans in full sun to partial shade. They’re not particular about soil type or fertility, although the soil must be well-draining. Keep the soil evenly moist while the plants become established. Space the plants at least 12 to 18 inches apart, so air circulates freely. Most black-eyed Susans grow between 2 and 3 feet tall and wide, although some have a compact or even vining habit.

Black Eyed Susan Flower Growing Tips

There’s not much to growing black-eyed Susans. Water them weekly during dry weather and fertilize them with a liquid all-purpose fertilizer if growth wanes or the leaves appear pale. The plants are subject to rust and mildew, but the damage is rarely serious. To prevent these diseases, space plants far enough apart so they’re not crowded. Avoid using overhead sprinklers, which can promote disease, and opt for drip systems and soaker hoses instead. Remove any diseased plant parts and destroy them.

Deadhead plants to promote more blossoms and cut them back midsummer if they start to become straggly. Shearing them will encourage compact growth and more blooms. Black-eyed Susans bloom from early summer to fall.

Varieties

Traditional black-eyed Susans are charming, but several new varieties are worth your attention. ‘Irish Eyes’ has lovely green cones instead of the more common brown or black, while ‘Bambi’ has flowers that range in color from pale yellow to red and brown. ‘Toto’ is a compact variety ideal for container culture. It grows only 12 inches tall. ‘Indian summer’ is prized for its large, yellow flowers, which can span 9 inches across.

In addition to these varieties, consider related species. Try giant coneflower (Rudbeckia maxima) a very large variety that grows up to 6 feet tall. ‘Goldsturm’ (Rudbeckia fulgida var. sullivantii ‘Goldsturm’) is a long-blooming, perennial variety.

Want to learn more about growing black-eyed Susans?

Black-eyed Susan from Colorado State University Extension

Coneflowers, Black-eyed Susans from the University of Kentucky Cooperative Extension Program

When she’s not writing about gardening, food and canning, Julie Christensen enjoys spending time in her gardens, which include perennials, vegetables and fruit trees. She’s written hundreds of gardening articles for the Gardening Channel, Garden Guides and San Francisco Gate, as well as several e-books.

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(Answer)

Thank you for contacting the Toronto Master Gardeners with your inquiry.

The golden flowers and black centers of black-eyed susan (Rudbeckia fulgida ‘Goldsturm’ ) are a welcome addition to any perennial border.These cheerful plants have a long bloom time (July-September) and depending upon the weather I have seen them flowering well into the end of October. Even after the petals have fallen off, the seedheads provide a beautiful architectural interest to the winter garden and as an added bonus provide much needed food for those birds that remain in our cold climate during the winter. A good rule of thumb to follow for transplanting any perennial is if they bloom in the fall, divide and transplant them in the spring. 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. This will cause them the least amount of stress. Planting them in the fall, again well before the first frost, has its advantages because it gives their roots time to become established before winter sets in, which will get them off to a faster start in the spring.

It is a good idea to add compost to your garden every year, it is never too late. Top-dress around perennials using organic material such as compost, shredded leaves or well-rotted manure. If using leaves as a mulch, consider leaving this on the beds in spring. This organic matter will soon decompose and add nutrient to the soil. Oak leaves are the exception because decomposition typically takes a long time.

Hydrangea paniculata, PeeGee type Hydrangeas bloom on new wood, so they can be pruned at any time in the spring or fall except when they begin to form flower heads in the summer. You might consider leaving the beautiful flower heads on these shrubs to add visual interest to your garden during the bleak winter months.

You may wish to read our Garden Guide on : Putting the Garden to Bed

I am revisiting this topic for two reasons: first, because it is one of my most searched posts this time of year, but also because I’ve recently found a great chart from the University of Illinois that lists 20 different insects that feed on various parts of black-eyed susans (Rudbeckia species). Granted, we most likely won’t all have all of those insects in our garden, but I do surely recognise a good number of them including the four-lined plant bug, the little nasty critter I keep insisting is responsible for the leaf damage to mine (the black spots).

You can access that chart here. One of the interesting things to note is that quite a few of the early insects listed are butterflies or moths. This means that the black-eyed susan is serving as the nectar plant for them–a very nice thing.

As you read further down the chart, any insect listed with an asterisk (*) next to its name feeds on the petals. That means it most likely is the nymphal stage of the butterfly, so it’s going to be a caterpillar. I know I for one don’t want to be in the habit of squashing caterpillars randomly, particularly ones that belong to butterflies. I’d rather endure petal damage.

Finally as you look down the chart you see my “baddie” the four-lined plant bug and some other true bugs. Now you have some hard choices to make. Knowing that you’ve got butterflies and their larva feeding on these plants, what do you do?

As you can tell by any damage in my garden, I tolerate the damage for the sake of nature.

Intereestingly, notice that one of the petals in the centermost flower has a notch taken out of it. I didn’t notice the damage until I uploaded the photo. Those semi-circular notches are made by leaf-cutting insects–bees or ants most likely. They do not harm the plant (other than by taking the piece of the petal or leaf away and visually disfiguring it). They use the piece taken away for nesting.

Leaf spot disease on a black-eyed susan.

Q: My black-eyed susans have black spots on the leaf that multiply until the leaf just dies. I’ve been treating them with a fungicide, but it just gets worse and worse. Is this a fungus or something else? What’s the proper treatment schedule for a fungicide?

A: That’s actually a fairly common disease on black-eyed susans cleverly called “leaf spot,” and it usually is at its worst in warm, humid weather (i.e. our typical August).

It is a fungal disease — most likely either Septoria or Cercospora. Fungicides can keep a lid on it, but the key is getting these sprays on at the onset of the disease and keeping the leaves treated as long as the weather is ripe for fungal growth.

At this point, it’s no doubt too late for any fungicide to be effective. The time to spray (if you’re a spray-prone gardener) is at the first sign of spotting on the lower or inner leaves.

Plant pathologists recommend weekly sprays to prevent the disease from getting a foothold. Chlorothalonil (Daconil) is a common fungicide that’s effective for this leaf spot disease. Organic gardeners can use copper-based fungicides.

You can do a few other things to discourage a repeat of the disease. One is to rake and remove fallen leaves since that’s a good source of spores to keep the disease active.

You might also try dividing and spacing out your plants a little. Crowded plantings can trap moisture on the leaves that encourage the disease. Airing them out helps the leaves dry better.

If that fails and you don’t want to keep spraying, replace the diseased black-eyed susans with another species, such as daylilies, coreopsis, salvia or gaillardia. Try new black-eyed susans (fresh ones, don’t move your diseased ones) in a different bed, or give the disease about 3 years to die out in the soil and replant with susans then.

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