Calathea
Calathea are popular houseplants prized for their leaves with graphic patterns a
1. Introduction
Calathea are popular houseplants prized for their leaves with graphic patterns and vibrant colors. Belonging to the Marantaceae family, they are native to the tropical forests of South and Central America. Their care requires a certain level of attention, particularly regarding humidity and light, which makes them suitable plants for experienced gardeners or enthusiasts of tropical plants.
This guide covers all aspects of Calathea, including biological, historical, cultural, commercial, and health-related aspects, with practical advice for both amateurs and professionals.
2. Biology and Classification
2.1. Taxonomy and Family
- Kingdom: Plantae
- Clade: Angiosperms
- Clade: Monocots
- Order: Zingiberales
- Family: Marantaceae
- Genus: Calathea
- Common Species:
- Calathea orbifolia (round leaves)
- Calathea lancifolia (narrow, elongated leaves)
- Calathea makoyana (peacock-shaped leaves)
- Calathea rufibarba (velvety leaves)
- Calathea zebrina (striped leaves)
- Calathea crocata (known for its bright orange flowers)
Source: Wikipedia - Calathea
2.2. Morphological Characteristics
- Habit: Herbaceous perennial plant, often acaulescent (without a visible stem), with leaves emerging directly from the ground via petioles.
- Leaves:
- Shape: Variable depending on the species (oval, lanceolate, round, arrow-shaped).
- Color: Green with complex patterns (stripes, spots, marbling) in light green, dark green, purple, pink, or silver.
- Texture: Some species have velvety leaves (C. rufibarba), while others are smooth and glossy.
- Movement: The leaves fold up at night (nyctinasty), a phenomenon related to light and humidity.
- Flowers: Relatively inconspicuous in most species, but some, like C. crocata, produce bright orange inflorescences. The flowers are generally small and grouped in spikes.
- Roots: Underground rhizomes that store nutrients.
2.3. Physiology and Ecological Needs
- Photosynthesis: Plants are C3 (unlike C4 or CAM plants, they do not have a mechanism for concentrating CO₂).
- Humidity: Requires high atmospheric humidity (70-90%) to prevent leaf desiccation.
- Light: Prefers indirect and subdued light (ideally 1,000–2,000 lux). Direct light can burn the leaves.
- Temperature: Optimum between 18°C and 25°C. Avoid drafts and temperatures below 15°C.
- Substrate: Well-drained soil, rich in organic matter (a mixture of peat, perlite, and compost).
3. History and Discovery
3.1. Geographical Origin
Calathea plants are native to the humid tropical forests of South and Central America, including:
- Brazil (Amazon region)
- Colombia
- Costa Rica
- Peru
- Ecuador
These regions offer a warm and humid climate, which is conducive to their growth.
3.2. Discovery and Introduction to Europe
- The first Calathea species were described by European naturalists in the 19th century, during scientific expeditions to South America.
- The genus Calathea was established by Augustus Pyramus de Candolle in 1821.
- Calathea plants became popular as houseplants in Europe and North America in the 20th century, thanks to their decorative foliage.
3.3. Historical and Cultural Uses
- Utility plants: Some species were used by indigenous peoples for their fibers (leaves of Calathea lutea used to make baskets).
- Traditional medicine: Certain varieties were used for their anti-inflammatory properties or to treat headaches (limited use, poorly documented scientifically).
- Ornamental plants: Today, they are primarily cultivated for their aesthetic value in interiors and tropical greenhouses.
4. Care and Maintenance
4.1. Ideal Growing Conditions
| Parameter | Optimal Value | Tolerance |
|---|---|---|
| Light | Indirect (1,000–2,000 lux) | Light shade (avoid direct sunlight) |
| Temperature | 18–25°C | 15–30°C (avoid <10°C) |
| Humidity | 70–90% | Minimum 50% (risk of drying out below) |
| Substrate | Airy mix (peat, perlite, compost) | Slightly acidic pH (5.5–6.5) |
| Watering | Keep the substrate moist (but not overly wet) | Allow the surface to dry slightly between waterings |
4.2. Watering and Water Quality
- Soft Water: Calatheas are sensitive to lime and chlorine. Use water that is:
- Rainwater (ideally)
- Filtered or demineralized
- Tap water left standing for 24 hours (to evaporate the chlorine)
- Frequency: Water when the top centimeter of the substrate is dry. Avoid standing water in the saucer (risk of root rot).
4.3. Fertilization
- Period: Spring and summer (active growth period).
- Fertilizer: Use a liquid, balanced fertilizer (NPK 10-10-10 or 20-20-20) diluted by half every 2–4 weeks.
- Winter: Reduce or stop fertilization.
4.4. Propagation
4.4.1. Division of Clumps (most common method)
- Period: Spring or early summer.
- Procedure:
- Remove the plant from its pot and carefully separate the rhizomes with the roots.
- Each division should have at least 2–3 leaves and healthy roots.
- Replant in fresh substrate and maintain high humidity.
- Success Rate: High if humidity conditions are maintained.
4.4.2. Stem Cuttings
- Period: Spring–summer.
- Procedure:
- Take a healthy stem with at least 2 nodes.
- Place in water or a moist substrate (perlite + peat).
- Maintain at 20–25°C with high humidity.
- Success Rate: Variable depending on the species.
4.4.3. Seed Propagation (rare for hybrids)
- Period: Spring.
- Procedure:
- Sow the seeds in a moist mix (peat + sand).
- Maintain at 25–30°C with high humidity.
- Germination may take several weeks.
- Note: Rarely used in commercial cultivation (Calatheas are often propagated by division).
Source: RHS - Propagating Calathea
4.5. Pruning and General Care
- Cleaning the leaves: Gently wipe with a damp cloth to remove dust (Calatheas are sensitive to mineral deposits).
- Removing dead leaves: Cut off yellow or damaged leaves at the base.
- Repotting: Every 2–3 years or when the roots come out of the pot.
5. Common Diseases and Problems
5.1. Water-Related Problems
| Problem | Causes | Solutions |
|---|---|---|
| Brown leaf tips | Lack of humidity, hard water | Increase humidity, use soft water |
| Root rot | Overwatering, poor drainage | Reduce watering, improve drainage, treat with a fungicide (e.g., Bordeaux mixture) |
| Dry leaf edges | Too dry air, lack of water | Mist regularly, use a humidifier |
5.2. Light-Related Problems
| Problem | Causes | Solutions |
|---|---|---|
| Pale leaves | Lack of light | Move closer to a window (indirect light) |
| Leaf scorch | Direct sunlight | Shade with a cloth or move |
5.3. Pests
| Pest | Symptoms | Treatments |
|---|---|---|
| Spider mites (Tetranychus urticae) | Fine webs, yellowing leaves | Increase humidity, use an acaricide (e.g., neem oil, insecticidal soap) |
| Scale insects (Diaspididae) | White, cottony masses, sticky leaves | Clean with a cotton swab dipped in 70% alcohol or use a systemic insecticide |
| Thrips (Thripidae) | Silver streaks, deformed leaves | Yellow sticky traps, insecticides (e.g., spinosad) |
| Aphids (Aphidoidea) | Sticky leaves, deformation | Spray with water, insecticidal soap |
5.4. Fungal and Bacterial Diseases
| Disease | Symptoms | Treatments |
|---|---|---|
| Gray mold (Botrytis cinerea) | Brown spots, gray mold | Remove infected parts, improve ventilation, treat with a fungicide |
| Leaf spots (Cercospora) | Brown or yellow spots on leaves | Remove affected leaves, avoid moisture on leaves |
6. Commercial Aspects
6.1. Popular Varieties and Their Characteristics
| Variety | Description | Price (approximate) |
|---|---|---|
| Calathea orbifolia | Round leaves, light green with concentric patterns. | €30–80 |
| Calathea lancifolia | Narrow, elongated leaves, dark green "V" patterns on light green. | €20–60 |
| Calathea makoyana | Peacock-shaped leaves, purple and green patterns on a light background. | €25–70 |
| Calathea rufibarba | Fuzzy leaves, dark green with red veins. | €35–90 |
| Calathea zebrina | Striped leaves, green and yellow patterns. | €20–50 |
| Calathea crocata | Green leaves, bright orange flowers (rare in indoor cultivation). | €40–100 |
| Calathea medallion | Round leaves with dark green, medallion-shaped patterns. | €30–75 |
| Calathea velvet | Velvety leaves, dark green with light veins. | €45–120 |
6.2. Where to Buy?
- Specialized nurseries (e.g., Pépinières du Val d'Erdre, Truffaut).
- Online stores:
- Plantes pour tous
- Bakker
- Amazon (pay attention to the quality of the plants).
- Plant markets (e.g., Marché aux fleurs de Paris, tropical greenhouses).
- Garden centers and hardware stores (e.g., Jardiland, Leroy Merlin).
6.3. Prices and Market
- Average price: Between €20 and €120 depending on the variety and size.
- Growing market: Calathea plants are becoming increasingly popular in Europe and North America, especially thanks to social media (Instagram, TikTok) which showcase their decorative foliage.
- Professional demand: Used in hotels, offices, and indoor green spaces for their tropical aesthetic.
7. Uses and Multifunctionality
7.1. Indoor Plant
- Decoration: Ideal for modern interiors, offices, and greenhouses.
- Air Purification: Like all plants, it contributes to the absorption of CO₂ and the humidification of the air (less effective than plants like Spathiphyllum or Sansevieria, but appreciated for its aesthetics).
7.2. Use in Landscaping (Tropical Zones)
- Ground Cover: Certain species (Calathea lutea) are used as ground cover in tropical gardens.
- Understory Plants: Suitable for shaded and humid areas of tropical gardens.
7.3. Other Uses
- Fibers: The leaves of Calathea lutea are used to make baskets and mats in Central America.
- Traditional Medicine: Some communities use the leaves for their anti-inflammatory properties (usage limited and poorly documented scientifically).
8. Sources and References
9. Appendices
9.1. Maintenance Calendar
| Month | Recommended Actions |
|---|---|
| January | Monitor humidity, avoid drafts |
| February | Check watering (reduce in winter) |
| March | Start fertilization, divide if necessary |
| April | Repot if needed, possible propagation |
| May | Increase watering, monitor for pests |
| June | Active propagation, monitor for diseases |
| July | Maintain humidity, protect from direct sunlight |
| August | Regular fertilization |
| September | Prepare for winter (reduce watering) |
| October | Clean leaves, check overall condition |
| November | Monitor temperature (avoid <15°C) |
| December | Reduce watering, avoid sudden changes |
9.2. Quick Diagnostic Chart
| Symptom | Probable Cause | Quick Solution |
|---|---|---|
| Leaves curling | Lack of water or dry air | Mist, increase humidity |
| Yellow leaves | Overwatering or lack of light | Adjust watering, move the plant |
| Fine webs under leaves | Spider mites | Increase humidity, treat with soap |
| Brown spots on leaves | Sunburn or fungal disease | Shade, treat with fungicide |