Coneflowers, or Black-eyed Susan are perfect plants for summer and autumn gardens.
Plant Biography
BOTANICAL NAME
Rudbeckia
COMMON NAME
Coneflower, Black-eyed Susan
NATIVE TO
These bright blooms are natively found in Canada and the USA.
DESCRIPTION
These flowers are bright, sunny, and perfect for strongly standing out in summer garden borders. Their daisy-like blooms feature a dark centre, hence the name ‘Black-eyed Susan’. Depending on the variety, the foliage can vary from hairy to smooth. It can also differentiate in colour, between green and grey.
What type of plant is it?
Rudbeckia are diverse when it comes to longevity. There are annual, biennial, and perennial varieties available. Most often in the UK, you will find hardy herbaceous perennial varieties are available.
What colours does Rudbeckia come in?
Whilst this plant is most commonly found in a golden yellow shade, they are also on offer in orange, dark red, and brown. There are also variegated options, combining some of these colours together for a fiery treat.
When do these plants flower?
The flowers take you through the end of summer through to mid-autumn, between August and October. They are the perfect autumnal shades for September and October displays.
Where does it like to grow?
These plants love well-draining soil, and positions with full sun. Some varieties, however, will cope well with light shade. Consider carefully where to position your Rudbeckias based on their ultimate height. Taller varieties will cope well at the backs of borders, whilst shorter varieties are better placed at the front.
Where does it dislike to grow?
Rudbeckias prefer not to sit in overly wet soil or fully shady spots.
Is this plant drought-tolerant?
Yes, these flowers are drought tolerant.
How to grow Rudbeckia successfully
Besides growing them in positions and soils that are well-suited, Rudbeckia are easy and low-maintenance plants to include in your garden.
They are neither particularly hungry nor thirsty plants either, just ensure they are watered well after planting, and during prolonged dry periods.
Annual coneflowers can be sown between February and April at temperatures of 20 to 25 degrees Celsius. Perennial varieties alternatively can be sown between February and July at between 18 and 20 degrees Celsius. Each can be transplanted once large enough to handle in individual pots. Then, harden them off in a cooler container for about 2 weeks before plating out.
Do they require supports?
Some of the taller varieties would benefit from some staking to give them extra support, yes. Otherwise, shorter varieties will cope perfectly well on their own.
Is it good for pollinators?
Yes, Black-eyed Susan flowers are popular with both bees and butterflies.
Is it good for wildlife?
Not only are Rudbeckia great for a variety of pollinators, but they also provide a source of food for birds. Once the seedheads mature, they make a great snack for winged garden visitors.
How to choose the right variety for your garden
If you want to grow Rudbeckias in containers, aim for dwarf annual varieties like Rudbeckia ‘Little Goldstar’. This lovely compact coneflower creates lovely drifts at the front of borders too.
Most coneflower varieties have wonderfully long stems making them perfect choices to add to cut flower displays. A striking dark chocolate-burgundy choice worth growing is Rudbeckia ‘Cherry Brandy’.
Finally, if you want varieties to suit different parts of the border, make sure you check their ultimate heights. For example, Rudbeckia laciniata can grow up to three metres tall, whilst Rudbeckia hirta ‘Toto’ only tops out at 25 cm.
How big will it get
The tallest you can expect taller-growing varieties to reach is approximately three metres or ten feet. However, you can get hold of varieties anywhere from 25 cm tall to this impressive three metres, just check the ultimate heights on the label.
How to plant Rudbeckia
Plant annual varieties after they have been hardened off in a cool location for a couple of weeks, before planting them in their final location. This final planting can be done between late May and early June, once all risk of frost has passed completely.
Alternatively, for perennial Rudbeckias, plant them out in spring between March and early May, into moist soil.
If you choose to grow from bare-root, make sure you plant them as soon as they are delivered. If you cannot plant them immediately due to unfavourable weather, ensure the roots don’t dry out.
Choose positions with full sun, or light shade if necessary. Make sure you dig in some well-rotted organic matter before planting, as Rudbeckias love fertile soil. Your prepared hole should be deep enough to take the rootball. Firm in, and water well.
How to care for Rudbeckia
Rudbeckias aren’t particularly hungry or thirsty plants, but make sure to water during prolonged dry periods. However, if growing in containers, they require your help a little more. Water more regularly, as often as daily if the weather is particularly hot.
Mulching your border Rudbeckias should be enough food each spring. If you have sandier soils, feed in the spring with a general fertiliser.
Container plants would occasionally benefit from some liquid fertiliser like Phostrogen or seaweed feed.
Do they spread?
Perennial varieties can after some time as their rhizomatous clumps grow underground. Rudbeckia laciniata is particularly well-known for growing vigorously this way, so life and divide every two or three years. The same applies to all other perennial Rudbeckias, to ensure they don’t get too congested.
How to keep it looking good
Coneflowers require very little help to keep looking good. Their low-maintenance nature means they will grow well and flower wonderfully with very little help. Regular deadheading of spent flowers will encourage additional blooms during their flowering season.
Does Rudbeckia need deadheading?
Deadheading Rudbeckias is particularly helpful for encouraging repeat flowering throughout the season. Simply remove faded flowers regularly. You can leave the faded flowers, however, for winter interest, and to allow the seedheads to form. This is also a great food source for visiting garden birds.
Does it need pruning, and when should they be pruned?
In the autumn, once all flowering has ceased, cut the growth all the way down to ground level.
How to propagate these plants
There are a couple of ways to propagate Rudbeckia plants. One way which may come naturally as you divide clumps every few years, is to replant any separated clumps as individual plants, and they should grow back strong the next summer.
Coneflowers can also be propagated by seed. First, sow the seeds thinly indoors between March and April in trays of moist compost. Cover lightly with a layer of compost, and cover with glass or a propagator lid to maintain a consistent temperature. You can also sow the seeds outdoors directly in May, onto a prepared seedbed.
What problems can Rudbeckia have?
Relatively trouble-free, you may find they suffer from powdery mildew and aphids.
For powdery mildew, look out for patches of white growing on the leaves. Remove and destroy these, and make sure there is plenty of space between plants to allow air in and reduce humidity. Remove any damaged material and destroy it, to try avoid a recurrence the following year.
Tolerate aphids if you can, and encourage their predators into the garden to deal with them for you. They shouldn’t cause significant damage to your plant either way.
Varieties of Rudbeckia to have
If you want particularly large Rudbeckias in your garden, Rudbeckia ‘Herbstsonne’ is one of the largest you can grow. It reaches an ultimate height of 2 metres, and a spread of 90 cm. Its large centres and bright yellow flowers is perfect for drawing attention to the back of garden borders.
Rudbeckia hirta, which is often grown as an annual in the UK, has many cultivars to suit your preferences. For example, ‘Cherry Brandy’ produces flowers in a delicious shade of chocolate-burgundy to enjoy. I also recommend ‘Cappuccino Bronze’, which has two-toned petals which bleed into yellow towards the tips.
I also find the lighter centre of Rudbeckia ‘Irish Eyes’ very striking, plus they produce some of the largest flowers out of any Black-eyed Susan variety.
Best time of year to buy this plant
You can buy container-grown perennial varieties of Rudbeckia throughout the year from garden centres and nurseries.
The best garden design style for this plant
You will most often find Rudbeckias performing wonderfully in prairie-style plantings, thanks to their autumnal flower shades.
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David Domoney is a Chartered Horticulturalist, Broadcaster, and Author. David has worked with a number of the UK’s leading garden retailers as a plant buyer and strategic consultant. With more than 30 years experience, in horticulture, David is as passionate about plants now as he was when he bought his first plant at a village fete.
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