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Plant care

Red Tower Ginger (Spiral Flag) care

Costus barbatus

Also called Spiral Flag, Red Pinecone Ginger, Barbados Costus.

RHS H1cUSDA 10-12Mildly toxic to petsIndoor 1.2-2 m tall

Watering rhythm

5-7days

When the top 2-3 cm of soil is dry, approximately every 5-7 days in the growing season; every 10-14 days in cooler months

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Light

Bright indirect light (just back from a sunny window)

Soil

Rich, loamy, well-draining tropical mix

Humidity

65-85%

Temp

18-32°C

Pet safety

Mildly toxic to pets

Mature size

1.2-2 m tall

Care at a glance

Light

Bright but filtered. Red Tower Ginger burns within days in unfiltered south-facing summer sun, and stops growing within months in deep shade. Grows best in bright indirect light or filtered sun. Can tolerate 2-3 hours of gentle morning direct sun outdoors. Insufficient light reduces bract production and causes stretched, weak stems. If you only have a south window, set the plant back 1.5 m or hang a sheer curtain — both knock the intensity down into the right range.

Watering

Watering red tower ginger: when the top 2-3 cm of soil is dry, approximately every 5-7 days in the growing season; every 10-14 days in cooler months. The number that matters isn't the day of the week — it's how dry the top 2-3 cm of the pot feels. A finger in the soil tells you more than a watering app. After every watering, tip the saucer. Keep soil consistently moist but not waterlogged throughout the growing season. Reduce watering in winter when growth slows. Ensure containers have adequate drainage to prevent rhizome rot.

Soil and pot

Red Tower Ginger grows best in rich, loamy, well-draining tropical mix. Use a blend of quality potting compost, perlite (20%), and coarse bark chips for moisture retention with aeration. High organic matter content supports the vigorous growth habit. 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

Red Tower Ginger sits happiest at around 65-85% humidity and 18-32°C (64-90°F). Thrives in high humidity replicating its Central American rainforest origins. Mist foliage daily, use a humidifier, or place on a pebble tray. Very dry air causes brown leaf edges and reduced flowering. If you keep the room above 18 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 red tower ginger sparingly. Feed with a balanced liquid fertiliser every 2 weeks from spring through late summer. A high-potassium feed applied monthly supports bract development and overall plant health. 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 red tower ginger in the Growli community. Each is annotated with the most common cause so you know where to start.

  • Brown leaf tips — Caused by low humidity or fluoride in tap water; raise humidity and switch to rainwater or filtered water.
  • Scale insects — Check the undersides of leaves and stem nodes; remove manually and treat with horticultural oil.
  • Leggy growth — Insufficient light causes stems to stretch; move to a brighter position or supplement with a grow light in winter.
  • Root rot — Excess moisture with poor drainage; repot into free-draining mix and reduce watering frequency.
  • No bracts developing — Typically linked to insufficient warmth or light; ensure minimum 20°C and a brightly lit position.

Companion plants

Red Tower Ginger pairs well with Heliconia psittacorum, Alpinia purpurata, Strelitzia reginae, and Etlingera elatior. 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

Divide rhizomes in spring or take stem cuttings with 2-3 nodes in summer. Cuttings root readily in moist perlite or propagation mix at 22-25°C. Division is faster for establishing large plants. 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

Red Tower Ginger is mildly toxic to pets. Costus barbatus is not listed in the ASPCA Toxic and Non-Toxic Plants database. The Costus genus in Costaceae has limited pet-toxicity documentation; as a precaution, classify as mildly-toxic. Seek veterinary advice if a pet ingests any part of the plant. 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.

Red Tower Ginger care — frequently asked questions

What is the common name for Costus barbatus?

Costus barbatus is most commonly called Red Tower Ginger, but it is also known as Spiral Flag, Red Pinecone Ginger, Barbados Costus. The names refer to the same species, so care instructions for Red Tower Ginger apply identically to anything sold as Spiral Flag.

How much light does red tower ginger need?

Red Tower Ginger grows best in bright indirect light (just back from a sunny window). Grows best in bright indirect light or filtered sun. Can tolerate 2-3 hours of gentle morning direct sun outdoors. Insufficient light reduces bract production and causes stretched, weak stems.

How often should I water red tower ginger?

Water red tower ginger when the top 2-3 cm of soil is dry, approximately every 5-7 days in the growing season; every 10-14 days in cooler months. Keep soil consistently moist but not waterlogged throughout the growing season. Reduce watering in winter when growth slows. Ensure containers have adequate drainage to prevent rhizome rot. 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 red tower ginger toxic to cats and dogs?

Red Tower Ginger is mildly toxic to pets. Costus barbatus is not listed in the ASPCA Toxic and Non-Toxic Plants database. The Costus genus in Costaceae has limited pet-toxicity documentation; as a precaution, classify as mildly-toxic. Seek veterinary advice if a pet ingests any part of the plant.

What USDA hardiness zone does red tower ginger grow in?

Red Tower Ginger is rated for USDA zone 10-12 (indoor-only in most US homes) and RHS hardiness H1c. Outside that range, grow it as a container plant that overwinters indoors before the first hard frost.

Red Tower Ginger deep-dive guides

Every aspect of red tower ginger care, each with its own calibrated guide:

Featured in these plant shortlists

Red Tower Ginger qualifies for 3 curated Growli shortlists — each one filtered objectively from our structured plant-care library, so the selection is consistent and checkable:

Related guides

Red Tower Ginger is also known as Spiral Flag, Red Pinecone Ginger, and Barbados Costus.