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Rudbeckia 'Denver Daisy' (Denver Daisy black-eyed Susan) care

Rudbeckia hirta 'Denver Daisy'

Also called Denver Daisy black-eyed Susan, Bicolour brown-eyed Susan.

RHS H6USDA 3-9Mildly toxic to petsIndoor 45-60 cm tall

Watering rhythm

7-10days

When the top 3-4 cm of soil is dry, roughly every 7-10 days

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Light

Direct sun (at least 4-6 hours)

Soil

Well-drained loamy or average garden soil

Humidity

30-60%

Temp

10-30°C

Pet safety

Mildly toxic to pets

Mature size

45-60 cm tall

Care at a glance

Light

Rudbeckia 'Denver Daisy' needs sun on the leaves, not just bright ambient room light. Full sun (6-8 hours) is essential for the best bicolour expression and sturdy stems. Plants in partial shade produce fewer flowers with duller patterning. A south or west-facing windowsill in the northern hemisphere is the default; anywhere else, expect the plant to stretch and pale out within a season.

Watering

Water rudbeckia 'denver daisy' when the top 3-4 cm of soil is dry, roughly every 7-10 days. The actual day count varies with pot size, light, and season — the finger test (or lifting the pot to feel its weight) is more reliable than a fixed calendar. Empty any drainage saucer afterwards so the pot isn't sitting in water. Drought-tolerant once established. Water deeply but infrequently. Avoid overhead watering to keep foliage dry and reduce disease risk.

Soil and pot

Rudbeckia 'Denver Daisy' grows best in well-drained loamy or average garden soil. Tolerates poor, dry conditions but performs best in well-drained loam. pH 6.0-7.0. Avoid heavy, compacted, or waterlogged soils. A pot with a working drainage hole is non-negotiable for this species — even free-draining mix will turn soggy in a closed planter. If you love the look of a decorative pot without a hole, use it as a cachepot around an inner nursery pot you can lift out to water.

Humidity and temperature

Rudbeckia 'Denver Daisy' sits happiest at around 30-60% humidity and 10-30°C (50-86°F). Not humidity-sensitive. Good spacing and airflow are sufficient to prevent powdery mildew in typical garden settings. If you keep the room above 10 year-round and avoid placing the plant near a cold draught, a hot radiator, or an air-conditioning vent, you have already handled the two biggest indoor stressors.

Fertilising

Feed rudbeckia 'denver daisy' sparingly. Apply a balanced slow-release granular fertiliser at planting. A mid-season liquid feed with a balanced formula can extend blooming. Avoid excessive nitrogen. Skip fertiliser entirely on a stressed, recently-repotted, or actively wilting plant — fertiliser salts make damage worse, not better. Wait for a round of healthy new growth before resuming a feeding rhythm.

Common problems

Below are the issues we see most often on rudbeckia 'denver daisy' in the Growli community. Each is annotated with the most common cause so you know where to start.

  • Powdery mildew — White powdery coating on leaves in still, humid conditions. Improve airflow and water at the base.
  • Aphids — Soft growth attracts aphids; treat with insecticidal soap or water jet.
  • Slugs — Target low foliage and stems; protect with grit or iron phosphate pellets.
  • Root rot — Caused by poor drainage. Amend soil before planting if waterlogging is a risk.
  • Floppy habit — In rich soils or shade, stems may flop. Grow in full sun with minimal feeding.

Companion plants

Rudbeckia 'Denver Daisy' pairs well with Salvia farinacea, Agastache foeniculum, and Gaillardia aristata. These are species with similar light and water needs, so you can group them in the same room or on the same shelf and water as a batch.

Propagation

Sow seeds indoors 6-8 weeks before the last frost at 18-21°C, pressing lightly onto the surface. Light is required for germination. Harden off and transplant after the last frost. Propagation is the cheapest, most satisfying way to expand a collection — and it doubles as insurance against losing a mature plant to an accident. Take a backup cutting once the parent is established and healthy.

Toxicity to pets

Rudbeckia 'Denver Daisy' is mildly toxic to pets. Rudbeckia hirta is not individually listed on the ASPCA toxic plants database. Mild gastrointestinal irritation is possible in dogs or cats if the plant is eaten. Treat as mildly toxic as a precautionary measure. If you keep cats, dogs, or curious children in the house, weigh placement carefully — a high shelf or a hanging planter is enough for casual safety. For severe ingestion incidents, call your local vet and the ASPCA Animal Poison Control Center (in the US, 888-426-4435).

Pet-safety status is sourced from the ASPCA Toxic and Non-Toxic Plant List, which catalogues the most-asked-about plants for cats, dogs, and horses.

Rudbeckia 'Denver Daisy' care — frequently asked questions

What is the common name for Rudbeckia hirta 'Denver Daisy'?

Rudbeckia hirta 'Denver Daisy' is most commonly called Rudbeckia 'Denver Daisy', but it is also known as Denver Daisy black-eyed Susan, Bicolour brown-eyed Susan. The names refer to the same species, so care instructions for Rudbeckia 'Denver Daisy' apply identically to anything sold as Denver Daisy black-eyed Susan.

How much light does rudbeckia 'denver daisy' need?

Rudbeckia 'Denver Daisy' grows best in direct sun (at least 4-6 hours). Full sun (6-8 hours) is essential for the best bicolour expression and sturdy stems. Plants in partial shade produce fewer flowers with duller patterning.

How often should I water rudbeckia 'denver daisy'?

Water rudbeckia 'denver daisy' when the top 3-4 cm of soil is dry, roughly every 7-10 days. Drought-tolerant once established. Water deeply but infrequently. Avoid overhead watering to keep foliage dry and reduce disease risk. The finger-test (or lifting the pot to feel its weight) beats a fixed weekly calendar because pot size, light, and season all change how fast the soil dries.

Is rudbeckia 'denver daisy' toxic to cats and dogs?

Rudbeckia 'Denver Daisy' is mildly toxic to pets. Rudbeckia hirta is not individually listed on the ASPCA toxic plants database. Mild gastrointestinal irritation is possible in dogs or cats if the plant is eaten. Treat as mildly toxic as a precautionary measure.

What USDA hardiness zone does rudbeckia 'denver daisy' grow in?

Rudbeckia 'Denver Daisy' is rated for USDA zone 3-9 (often grown as an annual) and RHS hardiness H6. Outside that range, grow it as a container plant that overwinters indoors before the first hard frost.

Rudbeckia 'Denver Daisy' deep-dive guides

Every aspect of rudbeckia 'denver daisy' care, each with its own calibrated guide:

Featured in these plant shortlists

Rudbeckia 'Denver Daisy' qualifies for 4 curated Growli shortlists — each one filtered objectively from our structured plant-care library, so the selection is consistent and checkable:

Related guides

Rudbeckia 'Denver Daisy' is also commonly called Denver Daisy black-eyed Susan or Bicolour brown-eyed Susan.