Everything You Need to Know About Growing Rudbeckias
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Rudbeckias, also known as Black Eyed Susans, are popular perennials (sometimes annuals or biennials) in the Asteraceae (Daisy) family.
The most common varieties delight with long stems supporting yellow petals around dark cones.
Typically reaching around 1 metre, some varieties will surprise and reach over 2 metres.
Rudbeckias are long-flowering and can be enjoyed from mid-summer well into autumn.
In this guide, we’ll explain how to grow perennial rudbeckias but the same advice will apply to annuals and biennial varieties.
We’ll also explain the subtle difference between rudbeckias and coneflowers.
Height: Usually around 1m but sometimes over 2m (6.4′)
Spread: Up to 40cm (3.2′)
Most rudbeckias are hardy herbaceous perennials – they die down to ground level and reappear in the spring. Watch out for rudbeckias with petals in colours other than yellow, these are usually annuals or biennials
Moderate growth rate. Rudbeckias may appear small and might not produce blooms in the first year but should reach full height by year 3
Easy if grown in a suitable location
Rudbeckias cope with the wind in an exposed site but will also thrive in a sheltered spot
Rudbeckias prefer full sun with soil that holds some moisture. They won’t produce as many flowers if grown in shade
UK H4-H6 rating – hardy in most parts of the UK except in the far north
Water & Feed
Rudbeckias thrive in full sun but dislike very dry soil, which ideally should be moist but free draining, especially if potted. There is no need to fertilise rudbeckias but a twice-yearly mulch with compost, leaf mould or similar will help
Rudbeckias are versatile perennials (sometimes annuals!) that can be paired with hundreds of other plants. Consider grouping with coneflowers, ornamental grasses, phlox, anemones and hardy geraniums
Place small plants up to 75cm (30″) apart in the spring, add leafmould, compost or other soil improvers as required. Start seed off indoors up to 10 weeks before the last frost. Bare roots can be planted at any time provided the ground isn’t frozen
Flowering season varies but is usually from mid-summer to mid-autumn. If rudbeckia seeds are sown late, they may not produce flowers in the first year
Get The Most From Rudbeckias: 12 Questions Expertly Answered
How and When are Rudbeckia Plants Sold?
Rudbeckias are sold as:
Seeds: Best sown indoors 10 weeks before the first frost date. If sown late, they may not flower in the first year or will only put on a limited show until year 2.
Plugs: Usually sold in garden centres from just after the first frost up until late summer.
Bare Roots: Usually available to pre-order from December with delivery at the end of winter or the start of spring.
Why Do Gardeners Grow Rudbeckias?
Rudbeckias are prairie plants and are usually grown for these reasons:
- Long stems that rarely break in the wind.
- They are long flowering, often over 2 months.
- Their downward-facing petals and dark cones.
- They mix well with most other plants and are perfect for mid-border spots.
- Rudbeckias are beneficial to pollinators.
How Should Rudbeckias be Planted?
Start off seeds 10 weeks before the first frost date to give them a head start and then plant directly into the soil just after the last frost.
Dig in compost or leafmould and water occasionally, until established.
Slugs and snails should ignore established plants from summer onwards but may nibble on young leaves in spring, so sprinkle a layer of organic slug pellets for the first few months.
Where Should Rudbeckias be Planted?
Rudbeckias will produce more blooms in full sun, and ideally in a spot with some moisture that’s also free-draining.
They dislike full shade and will only put on a limited display in part-shade.
Rudbeckias can be planted in the middle of a border amongst other plants or in pots on a sunny path or patio.
Do Rudbeckias Need Watering and Fertiliser?
Apply a twice-yearly dose of compost or leafmould, worked into the soil, and you can’t go wrong.
There is no need to apply fertilisers unless the soil is very poor.
Rudbeckias are less tolerant of dry soil than coneflowers and although they will survive overly dry conditions, their growth may be stunted.
The best soil is one that’s slightly moist but free draining and never waterlogged.
Do Rudbeckias Set Seed? Are They Invasive?
Rudbeckia cones will harden towards the end of summer and into autumn and then seeds will drop out.
The seeds often germinate easily and rudbeckias are known for spreading but they are rarely invasive in the UK and can be controlled with little effort.
Birds love the seeds, so don’t be surprised if you see rudbeckias popping up at the other end of the garden where birds have dropped the seeds.
What Pests and Diseases Affect Rudbeckias?
Rudbeckias are tough plants that hold up well against diseases and most pests.
Slugs and snails may nibble on young leaves in the spring but they rarely bother by summer.
Powdery mildew and brown leaf spot may affect rudbeckias. Avoid overhead watering and splashing as this spreads diseases.
How Long Do Rudbeckias Flower For?
Rudbeckias usually produce flowers from mid-summer through to autumn.
Can I Grow Rudbeckias in Containers?
Yes, but they may struggle in overly dry soil and heatwaves, so water more frequently and top up with compost throughout the growing season.
Are Rudbeckias Poisonous to Humans or Pets?
Are Rudbeckias Beneficial to Wildlife?
Bees, butterflies and other pollinators love single-flowered rudbeckias (the most common type) and birds will take the seeds, often well into the winter if you leave the cones in place.
How Difficult are They to Grow?
If rudbeckias are grown in full sun, in slightly moist soil, you’ll find them very easy to grow.
Rudbeckias struggle in shade or waterlogged soil and during heatwaves they may wilt.
Caring For Rudbeckias After Flowering
In most parts of the UK, rudbeckias will grow as hardy, herbaceous perennials, meaning they lose their leaves and stems in the winter, die back to ground level and then reappear in the spring.
Prune and Deadhead
Deadhead flowers as they start to fade as this will encourage new flowers to appear and will prolong the flowering season.
Leave the cones on the stems and they will attract birds and set seeds.
There is no need to prune rudbeckias as they will die down naturally.
Feed and Fertiliser
There is no need to apply feed or fertiliser after flowering.
The best time to mulch is in the spring and summer but if grown in very cold climates (below minus 10), a late autumn mulch can protect the roots and crown from frost.
Protect From Winter Wet
Rudbeckias prefer slightly moist but well-drained soil and may struggle in waterlogged ground conditions.
Lifting and Dividing
Rudbeckias spread by rhizomes and by seeds so the area they are grown in can become congested. Consider lifting, dividing and even thinning out such areas every 3-4 years.
Rudbeckias are versatile plants that mix well with hundreds of other plants, inc:
- Bee balm.
- Ornamental grasses.
- Hardy geraniums as a ground cover plant.
Consider these varieties:
Rudbeckia “Goldsturm”: This is one of the most popular rudbeckias. Expect growth up to 60cm and star-shaped petals around a dark central cone. Hardy and versatile, this perennial rudbeckia is the best for beginners.
Rudbeckia “Cherry Brandy”: Best grown as an annual, this half-hardy rudbeckia delights with deep crimson red petals and is long flowering, often opening up from early July and lasting through to the autumn.
Also, consider coneflower/rudbeckia crosses such as “Berlin” as shown on the Dorset Perennials website.
10 Key Points
If you’ve never grown rudbeckias before, consider these 10 points:
- Classic yellow rudbeckias such as R. goldsturm are perennials in the UK while most of the red, orange and darker coloured rudbeckias are half hardy and usually grown as annuals.
- While often grown with coneflowers, rudbeckias are more sensitive to dry soil and prefer some moisture.
- If rudbeckias look stunted or shrivelled, it’s almost always due to overly dry soil.
- The tall stems on rudbeckias look magnificent rising above foliage-heavy plants such as hardy geraniums.
- Rudbeckias are well suited to containers but will require more frequent watering.
- Rudbeckias vary in size with the popular perennial R. goldsturm reaching 60cm while R. laciniata can reach up to 3m.
- Rudbeckias grow in clumps and spread via seed and rhizomes but are never a nuisance although they may need to be divided and thinned out every few years.
- You’ll find that rudbeckias make excellent cut flowers.
- Consider buying established bare root rudbeckias so you reduce plastic waste (no pots) and get them off to an early start.
- Rudbeckias are easy to grow and reliable, they look stunning in any garden and mix well with most plants.
A Quote From Daniel, Our Co-FounderHere is a quote from Daniel, our co-founder:
I currently have R. goldsturm in my borders and although they were slow starters in year one, they are now in full swing and look delightful mixed in with coneflowers. During the recent heatwave (2022) they did wilt and needed extra watering, but otherwise they have been hassle-free. I grow hardy geraniums around the rudbeckias to add low-level interest as rudbeckia flowers are 60cm above the ground.
The Difference Between Coneflowers and Rudbeckias
Coneflowers (Echinacea purpurea) and rudbeckias are two separate genera from the Asteraceae (Daisy) family.
They are very similar and are often grown together.
Visually there are a few differences:
The cones on rudbeckias are usually darker, hence the nickname “Black-Eyed Susans”.
The cones on coneflowers are spiky but on rudbeckias, they are softer.
Coneflower cones are sometimes slightly pointed rather than perfectly rounded.
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More From Hannah Miller:
Hannah Miller wrote this guide to growing rudbeckias which forms part of her Summer Flowering Plants Collection.
Hannah is a keen gardener who is trying to reduce her use of pesticides and move to organic gardening.
She’s also a mother and former NHS administrator with 12 years of experience. She also speaks English, Russian and Ukrainian fluently and enjoys travelling around Europe.
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