Planting rudbeckia: when, where & how

The richly flowering black-eyed Susans are one of the most popular autumn perennials. Get tips on growing and planting rudbeckia in beds and containers.

Rudbeckia, also known as coneflowers or black-eyed Susans, are low-maintenance and long-flowering perennials. Find out all about propagating and planting rudbeckia and which plants make good companion plants.

Planting rudbeckia

When it comes to planting rudbeckia, you can either sow your own rudbeckia seeds or buy young plants from your local garden centre or plant nursery. Read on for more information about planting rudbeckia, including where and when to plant them, ideal growing conditions and how to propagate the flowers.

Where to plant rudbeckia

If you want to grow black-eyed Susans in your garden or on your balcony, you first need to choose a suitable spot. They prefer fresh to moist, nutrient-rich and well-draining soil and like full sun. For more information on the exact requirements of different species, see our article on rudbeckia species. When growing rudbeckia in pots on balconies and terraces, opt for a nutrient-rich soil that retains water well. Our pre-fertilised and completely peat-free Plantura Organic Flower Compost contains essential nutrients that will feed your black-eyed Susans in the early days after planting. It also has a high compost content which retains water well and releases it to the plant roots when needed. To further increase the water retention capacity, mix in some bentonite (clay powder).

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Which location is ideal for planting rudbeckia?

• Sunny, some species also thrive in partial shade
• Fresh to moist, but well-draining soil
• Locations with a good supply of nutrients

Sowing and planting rudbeckia

Perennial coneflowers are available to buy in most nurseries. However, some species and varieties are short-lived and must be propagated annually by seed. Start rudbeckia seeds indoors between February and mid-April or sow directly in the garden once the temperature of the soil rises between April and May. You can use plastic bowls or small pots for starting coneflowers indoors. To do this, loosely sow the rudbeckia seeds into slightly moistened, nutrient-poor growing medium, such as our Plantura Organic Herb & Seedling Compost. Cover the seeds with a thin layer of soil, about 0.5 cm thick. Water carefully and cover with a clear plastic bag to ensure a high level of humidity. Rudbeckia seeds usually germinate after 14 to 21 days when placed on a bright, warm windowsill at 18 to 22 °C. After a few weeks, prick out individual seedlings and transplant them into small pots with nutrient-rich potting soil as soon as they have grown two true leaves.

Sowing rudbeckia seeds:

• Start indoors from February; sow directly in garden from April in nutrient-poor growing soil
• Spread seeds evenly, cover with 0.5 cm of soil, and water
• Germinate in 2 – 3 weeks at 18 – 22 °C in sufficient light and moisture
• Prick out once true leaves have grown and transplant into nutrient-rich potting soil

But when is the ideal time to plant black-eyed Susans? The best time for planting rudbeckia is during the frost-free periods in late autumn from September to the end of October, or from March onwards. Coneflowers that have been started indoors prefer to be planted outdoors around mid-May to June, after the last cold spell. Keep a planting distance of around 25 to 30 cm for annual rudbeckias, and about 60 to 90 cm for bushier, wider growing species.

Before planting rudbeckia, prepare suitable planters or beds. When growing rudbeckia in pots, choose pots with the capacity to hold at least 20 to 30 litres of soil. The bottom five to 10 cm serve as a drainage layer, so fill this portion with gravel, expanded clay or sand before adding the soil and lightly press it down. As long as they have sufficient drainage, smaller containers and balcony boxes are suitable for annual coneflowers too.

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When planting rudbeckia in a bed, remove any weeds beforehand and loosen a large area of soil down to a depth of about one spade. You can also take this opportunity to enrich poor or sandy soil with mature compost to improve nutrient reserves and water retention capacity. Next, dig a large planting hole with a spade or a hand shovel. Plant the black-eyed Susans into the ground, deep enough that the soil reaches the same level as in the pot, then press down lightly and water well.

Tip: Some rudbeckia species, such as Rudbeckia nitida, are particularly susceptible to snails, so it may be necessary to use pest-control methods to ward them off.

Rudbeckia companion plants

Depending on the species, coneflowers can be planted individually or in small groups of three to ten to showcase their rich blooms. Tall and vigorous species such as the giant coneflower (Rudbeckia maxima) or the cut leaf coneflower (Rudbeckia nitida) should be planted individually. Low-growing varieties such as the brown-eyed Susan (Rudbeckia triloba), on the other hand, can be planted in groups and will quickly develop into a beautiful, unobtrusive sea of flowers. When planting rudbeckia in garden beds, it is important to consider which plants they combine well with. Rudbeckia combine well with flowers with staggered flowering times and contrasting colours or, to create a varied perennial bed, you can also plant them with grasses. The following species are suitable rudbeckia companion plants:

• Giant hyssop (Agastache)
• Vervain (Verbena)
• Grasses such as moor grass (Molinia), blue grama (Bouteloua gracilis), switchgrass (Panicum virgatum), quaking-grass (Briza media)
• Aster (Aster)
• Bergamot (Monarda)
• Larkspur (Delphinium)
• Sage species (Salvia)
• Coneflowers (Echinacea)
• Sunflowers (Helenium)
• Cranes-bill (Geranium)

Propagating black-eyed Susans

It is possible to propagate rudbeckia by seed, division or, as with some varieties of Rudbeckia hirta, by rhizome tubers. Dividing rudbeckia is the simplest and most reliable propagation method. Divide the plants in early spring when new shoots appear, from mid-February to the end of March. Use a sharp spade to cut a small section with good roots off, then dig it out and plant it in another suitable location. Alternatively, you can dig the rhizomes of tuber-forming black-eyed Susans up and transplant them without damaging them.

Rudbeckia seeds can be collected in late autumn from September to November. While black-eyed Susan seeds are easy to collect and store, if other species or varieties of rudbeckia are in the vicinity, the seeds will often not have varietal purity. Annual black-eyes Susans begin to wither in late autumn. To collect the seeds, cut off the dry seed heads from the plants that are turning brown and leave to dry indoors at room temperature for a few weeks. The elongated seeds usually fall out of the conical flower heads by themselves. Store the rudbeckia seeds in a dark, dry and cool place.

Aside from rudbeckia, there are many other perennials that bloom until late autumn. See our article for the 10 most beautiful autumn flowers for your garden.