Cryptanthus (Earth Stars): How to Grow and Care in Terrarium?

Cryptanthus, commonly known as Earth Stars, are a genus of bromeliad plants that are native to eastern Brazil. With their compact size and colorful leaf markings, Cryptanthus make excellent choices for terrarium culture. Here is a complete guide on how to grow and care for these dazzling plants in an enclosed terrarium environment.

What are Cryptanthus (Earth Stars)?

Cryptanthus are a genus of around 250 species of evergreen, perennial flowering plants in the Bromeliaceae (bromeliad) family. They earned the common name “Earth Stars” from their striking foliage that spreads out like a star against the ground.

The foliage of Cryptanthus varies from green to brown, red, orange, yellow and purple, often with contrasting bands, stripes or mottling. The undersides of the leaves are usually colored bright red or purple. Mature Cryptanthus reach a size of 3-6 inches in diameter and grow in a rosette pattern with the leaves emerging from the center.

Small white or blue flowers may occasionally emerge from the centers of the rosettes. However, Cryptanthus are primarily grown for their decorative foliage as opposed to the relatively insignificant flowers.

Native to the coastal mountains and rainforests of southeastern Brazil, most Cryptanthus species are terrestrial, growing on the forest floor rather than on trees. They tend to thrive in shady, humid environments in their native habitat.

How to Choose Cryptanthus for Terrarium?

With so many Cryptanthus species available, it can be daunting to select the right ones for your terrarium. Consider the following factors when choosing Earth Stars for an enclosed environment:

Size: Select petite Cryptanthus varieties that can comfortably fit inside a terrarium. Larger species may outgrow the space. Good terrarium choices include C. bivittatus, C. fosterianus, and C. zonatus.
Color: Choose Cryptanthus with vivid foliage colors like red, orange, pink or yellow to create a striking contrast against the green backdrop of a terrarium. Popular picks include C. pink starlite and C. beuckeri.
Moisture Needs: Some Cryptanthus require more moisture than others. High humidity-loving species like C. warasii and C. sinuosus are ideal for terrariums. Avoid super drought-tolerant varieties.
Light Requirements: Select shade-loving Cryptanthus that can thrive under the lower light conditions inside a terrarium. Avoid full sun lovers like C. acaulis.
Hybrids: Cryptanthus hybrids and cultivars bred specifically for container culture, like the Cryptanthus Earth Angel series, are great terrarium candidates.

What are the Preferred Growing Conditions for Cryptanthus in Terrariums?

Cryptanthus housed in terrariums require the following optimized growing conditions to maximize their health and appearance:

Temperature

Cryptanthus prefer warm temperatures between 60-80°F (15-26°C). Avoid exposing them to temperatures below 50°F (10°C) which can damage the foliage. Maintain the terrarium in a warm, indoor location away from cold windows, doors or drafts.

Lighting

Though bright light will bring out the best leaf colors, most Cryptanthus cannot tolerate direct sunlight inside a terrarium. Provide 50-75% shade by using a sheer curtain or keeping them a few feet away from a bright window. Indirect natural lighting is ideal. Fluorescent growing lights can supplement lower indoor light.

Humidity

Humidity is key! Cryptanthus demand very high, constant humidity levels of at least 60-80% to replicate their native rainforest environment. Anything below 40% can quickly damage their foliage. Always keep the terrarium covered and frequently mist the plants to boost moisture levels.

Watering

Water Cryptanthus whenever the top 25% of the potting mix has dried out, usually once or twice a week. Pour water directly into the potting medium until it drains from the drainage holes below. Avoid letting plants sit in stagnant waterlogged soil.

Air Circulation

Stagnant, stale air can encourage fungal rot and decline. Improve air flow by gently stirring the air once a day with the terrarium open, or use a small battery-powered fan if the container is large enough.

Potting Media

Use an organic, peat-based potting mix amended with orchid bark, perlite or pumice to provide good drainage and aeration. Live moss makes an attractive top-dressing.

Fertilizer

Apply a balanced liquid fertilizer like 20-20-20 diluted to 1/4 strength once a month during active growth periods. Excess fertilization can damage roots in an enclosed terrarium.

How to Plant Cryptanthus in a Terrarium?

Planting Cryptanthus in a terrarium is easy. Follow these simple steps for proper arrangement and acclimation:

Choose Shallow Pots

Select wide, shallow pots no more than 2-3 inches deep. This prevents roots from suffocating in cramped quarters. Plastic pots are fine, just watch for condensation buildup on the insides in humid conditions.

Use an Open Potting Mix

Fill pots about 3/4 full with the recommended porous potting media. Do not pack it down tightly. Leave 1/4 inch headspace below the rim so the mix can dry out between waterings.

Remove Rhizomes from Old Mix

Carefully loosen old potting mix clinging to the roots and rhizomes before repotting. Keep the rhizome intact and do not damage thick, fleshy roots.

Plant at Same Depth

Arrange plants in pots at the same depth they were growing at previously. Burying crowns or rhizomes too deeply leads to rot. Plant just deep enough to anchor.

Allow Time to Acclimate

Keep freshly planted Cryptanthus drier than usual for 2-3 weeks until established. Slowly transition to higher humidity and moisture levels for the enclosed terrarium environment.

Top Dress with Moss

Add an attractive top layer of live sheet moss around plants if desired once acclimated. This helps lock in humidity and prevent soil erosion during watering.

How to Provide Proper Ongoing Care for Cryptanthus in Terrariums?

Caring for terrarium-grown Cryptanthus is focused on maintaining ideal humidity, light and air circulation conditions inside the enclosed container:

Monitor Humidity Regularly

Check humidity levels several times a week with a hygrometer. Mist plants daily or use a pebble tray to keep relative humidity consistently between 60-80%.

Allow Medium to Partially Dry

Water thoroughly only after the top portion of the potting mix starts to dry out. Sticking your finger 1-2 inches into the soil is a good gauge. Never let plants sit in soggy mix.

Open Lid for Air Exchange

Remove the terrarium lid for 30-60 minutes each day to allow for air exchange and circulation. This prevents excess moisture buildup inside.

Provide Bright Indirect Light

Situate terrarium near a bright window filtered by a sheer curtain. Rotate every few days to distribute light exposure evenly. Supplement with fluorescent grow lights during darker months.

Look for Pest or Disease Issues

Inspect closely for common pests like scale, mealybugs and spider mites which thrive in confined humid conditions. Also watch for signs of fungal or bacterial diseases.

Divide When Overcrowded

Gently divide and repot when the foliage of multiple plants start to overlap inside the terrarium. This prevents moisture-related diseases.

Remove Flowers and Offsets

Nip off any flowers as they appear to conserve the plant’s energy. Also carefully remove baby plantlets or “offsets” to prevent overcrowding.

Fertilize Sparingly

Apply diluted liquid fertilizer just once every 4-6 weeks. Overfeeding can burn roots and leaves in a restricted environment. Flush soil occasionally to prevent salt accumulation.

What are the Best Companion Plants for Cryptanthus Terrariums?

Here are some pleasing companions to pair with Cryptanthus in high-humidity terrariums:

Tropical Foliage Plants

Choose small tropicals like nerve plants, polka dot plants, prayer plants and baby’s tears for contrasting leaves and texture. Avoid aggressive spreaders.

Moss

Cushiony sheets of mood moss make the ideal terrarium carpeting around Cryptanthus pots. Keep them moist and they’ll thrive. Popular types include Java, sheet, and cushion moss.

Air Plants

Miniature Tillandsia air plants like T. baileyi, T. balbisiana, and T. streptophylla combine well with Cryptanthus both visually and culturally.

Creeping Ferns

Delicate creeping ferns like rabbit’s foot fern, maidenhair, and button fern intermix nicely and share the preference for humidity.

Miniature Orchids

Compact orchids that relish humidity like Bulbophyllums, Neofinetias and Aerangis match the scale and growing conditions of Cryptanthus. Mount them on natural wood.

Avoid larger, more demanding orchid varieties and houseplants that require much drier conditions. Select all terrarium-bound plants with similar light, watering, humidity and temperature needs.

Are Cryptanthus Suited to Open or Closed Terrariums?

Cryptanthus adapt quite flexibly to both open and closed terrariums depending on the ambient humidity of your indoor environment:

Open Terrariums

In dry indoor settings, an open terrarium design provides better airflow and allows more frequent air exchange through the unsealed entry. This may help reduce fungal disease. Open terrariums require more frequent misting however.

Closed Terrariums

In naturally humid climates or rooms, a completely sealed “Wardian case” type enclosed terrarium better contains the needed high humidity levels for healthy Cryptanthus. Ensure the seal has proper ventilation.

Modifications Possible

Terrariums can be modified over time too. For example, a closed terrarium may need increased ventilation openings as plants mature and fill in space. Or you can switch an open design to closed during drier weather.

Adapt the terrarium style to create the ideal microclimate based on your environment. Monitor Cryptanthus health and make changes to enclosure ventilation as needed.

What Basic Supplies are Needed to Grow Cryptanthus in Terrariums?

Growing Cryptanthus in terrariums is relatively simple. You only need a few basic supplies:

A clean glass container such as a large jar, apothecary jar or fish bowl. Size it appropriately for selected plants.
Small but deep pots, preferably with drainage holes, to plant each Cryptanthus specimen.
An organic, porous potting mix amended with orchid bark or perlite for aeration.
Sheet moss or small pebbles for top-dressing around pots.
Distilled water or rainwater. Tap water may leave mineral deposits on glass.
A hygrometer to monitor humidity levels inside the enclosed environment.
Optional sheer curtain to provide bright shade if placing terrarium near a sunny window.

Avoid overcrowding the container. Select 1-3 small Cryptanthus in 3-5 inch pots as suitable for most tabletop terrariums. Larger specimens need more root room.

What are the Troubleshooting Tips for Growing Cryptanthus in Terrariums?

Growing Cryptanthus in terrariums comes with some unique challenges. Here are some troubleshooting tips for common problems:

Declining Health

If plants show signs of decline like softened or rotting leaves, poor color or slow growth, the main culprits are usually improper moisture levels or insufficient lighting.

Leaf Spotting

Discolored or spotted foliage can indicate bacterial or fungal infection in the persistently moist environment. Improve air circulation and drainage to clear up diseases.

Weak Leggy Growth

If new leaves emerge small and stunted or on long petioles, it indicates insufficient light. Provide brighter filtered exposure or supplemental grow lights.

Failure to Bloom

Lack of flowering is natural as Cryptanthus won’t bloom readily in low light. But also watch for overheating or abrupt location or temperature changes which can disrupt flowering.

Pest Infestations

Spider mites, scale and mealybugs thrive in the high-humidity of terrariums. Isolate plants and treat with horticultural oils or insecticidal soap sprays if pests are detected.

With good air flow, stable temperatures, filtered light, regulated humidity and proper watering, Cryptanthus thrive beautifully in terrarium culture. Make adjustments promptly when issues emerge to maintain healthy growth.

How to Design an Attractive Cryptanthus Terrarium Display?

When designing the layout of your Cryptanthus terrarium, follow these design tips for creating an artful display:

Use Contrasting Colors

Select Cryptanthus with brightly contrasting bicolor foliage, like orange and green, to create striking color combinations. Vivid red or yellow plants also stand out nicely against greens.

Complement Shapes

Pair Cryptanthus with diverse leaf shapes and textures. For example, fluffy ball-shaped Cryptanthus looks great next to fine, grassy Tillandsias.

Choose a Neutral Background

Keep the container interior neutral colored, either transparent or tinted black or gray. This prevents competing with the colorful plants.

Highlight Unique Container

Display intricately shaped or artistic terrariums like hanging glass bubbles or geo-shaped containers to show off the design along with the plants.

Include Natural Elements

Incorporate found objects from nature like smooth stones, shells, seed pods or bark pieces. Miniature figurines also add whimsy.

Light from Above or Side

Illuminate the terrarium display with either top-down or side lighting to highlight colors and textures. Use grow lights or small LEDs.

Bring out the inherent beauty of Cryptanthus through thoughtful terrarium design principles. Artfully combine colors, forms, lighting and materials to create a unique living work of art.

Can the Terrarium Environment Fully Substitute the Natural Habitat of Cryptanthus?

While terrariums allow us to successfully grow moisture-loving Cryptanthus as houseplants, they cannot fully replicate the plants’ natural habitat in the following ways:

Light Duration

Outdoors, Cryptanthus receive much brighter light and longer photoperiods. Replicate this as much as possible indoors to maximize growth and coloration.

Air Movement

Terrariums restrict air flow compared to the constant breezes and circulation of the plants’ native rainforests. Provide periods of ventilation to refresh stale air.

Root Space

Containers restrict root development. Repot frequently into fresh mix in the same small pots or replate divisions to prevent root-bound stress.

Nutrient Cycling

The closed system of a terrarium cannot mimic the natural breakdown and recycling of leaf litter and organic debris on a forest floor.

Biodiversity

The ecosystem of a terrarium is far less complex than the diverse mosses, plants, microbes and fauna of a rainforest soil biome.

Terrariums offer only an approximation of a Cryptanthus’ native habitat. Provide the most optimal artificial conditions possible to ensure health and vigor.

What are the Key Takeaways of Growing Cryptanthus in Terrariums?

Here are the key tips to remember when cultivating Cryptanthus in high-humidity terrarium environments:

Select small, shade-loving varieties with vibrant bicolor foliage.
Plant in shallow pots using loose, well-draining potting media.
Acclimate plants gradually to higher consistent humidity levels.
Provide bright, indirect light for at least 8-10 hours daily.
Allow potting mix to partially dry out between thorough waterings.
Improve air circulation and exchange daily.
Monitor for pests and diseases frequently.
Repot or divide when overcrowded.
Fertilize very lightly 1/4 strength every 4-6 weeks.
Combine with small tropical foliage plants, mosses and air plants.

With the right species, cultivars and care tactics, growing Cryptanthus Earth Stars successfully in home terrariums is an achievable and enjoyable endeavor for both novice and expert gardeners alike!