Anthurium watermaliense aka Black Anthurium

Anthurium watermaliense is a moderately challenging houseplant best suited for growers with some experience. It demands consistently high humidity (60–80%), warm temperatures, and a well-draining aroid substrate — conditions that require more attention than typical beginner plants. However, once its environment is dialed in, it is relatively forgiving and rewards consistent care with impressive dark-spathed blooms and lush foliage.

Anthurium watermaliense typically reaches about 1 meter (3 feet) in height and 80 cm in spread when grown indoors. It grows in a rosette or "bird's nest" form with deeply lobed, heart-shaped leaves measuring 21–60 cm long on petioles that can extend up to 88 cm. Growth rate is moderate, and the plant develops a short stem of up to 25 cm with compact internodes.

Anthurium watermaliense thrives in temperatures between 18–27°C (65–80°F) and can tolerate up to 32°C (86°F). It should not be exposed to temperatures below 15°C (59°F), as cold damage can occur. In regions with cool winters, keep it indoors or in a heated greenhouse. Avoid placing it near cold drafts, air conditioning vents, or heating sources that create temperature fluctuations.

The inflorescence is the plant's most striking feature. It consists of a dark violet-purple spathe — so deeply colored it appears nearly black — and a spadix that emerges white then matures to greenish-yellow or tan. The spadix sits on a distinct stipe (short stalk), which is unusual for its section. After pollination by beetles, the plant produces ovoid yellow to orange berries. The spathe is lanceolate-triangular and typically reflexes and twists as it matures.

Anthurium watermaliense can be propagated by division or from seed. Division is easiest — during repotting, gently separate offsets that have their own root system and at least 2–3 healthy roots. Seed propagation is possible but slow: sow fresh seeds on moist sphagnum moss, maintain high humidity and warmth (21–27°C), and expect germination in 2–6 weeks. Seedlings grow slowly and may take 2–4 years to reach maturity.

Repot Anthurium watermaliense every 2–3 years or when roots begin circling the pot. Choose a container only 5 cm (2 inches) larger than the current one — these plants prefer being slightly rootbound. Terracotta pots with drainage holes work well as they allow the substrate to breathe. Use a fresh chunky aroid mix of orchid bark, perlite, charcoal, and sphagnum moss. Spring is the best time to repot.

Anthurium watermaliense is low-maintenance when it comes to pruning. Remove yellowed, damaged, or spent leaves and faded inflorescences as needed to keep the plant tidy and redirect energy to new growth. Use clean, sharp scissors or pruning shears to prevent infection. Occasional pruning also helps improve air circulation around the plant, reducing the risk of fungal issues.

Anthurium watermaliense can grow outdoors year-round only in USDA zones 10–11, where temperatures stay consistently above 15°C (59°F). Plant it in a shaded or dappled-light location protected from direct sun and wind. In cooler climates, it makes an excellent patio plant in summer but must be brought indoors before nighttime temperatures drop below 15°C. It cannot tolerate frost.

Anthurium watermaliense is native to the premontane and lower montane rainforests of Costa Rica, Panama, and Colombia. It grows terrestrially on the forest floor at elevations from near sea level to approximately 2,500 meters, though most specimens are found below 750 meters. The species was first collected from Central America and brought to cultivation at Watermaal (Watermael) in Belgium, from which it takes its name.

Yellow leaves on Anthurium watermaliense most commonly indicate overwatering or poor drainage, which leads to root rot. Check that the substrate is well-draining and that the pot has adequate drainage holes. Other causes include insufficient light, nutrient deficiency (especially nitrogen), or natural aging of older lower leaves. If multiple leaves yellow rapidly, inspect the roots for soft, brown, mushy tissue — a sign of rot that requires immediate repotting into fresh substrate.

Brown leaf tips or edges on Anthurium watermaliense typically signal low humidity — this species requires 60–80% humidity. Brown patches or scorched areas may result from direct sunlight exposure, which burns the foliage. Crispy brown tips can also indicate underwatering, salt buildup from fertilizer, or exposure to cold drafts. Increase humidity with a humidifier or pebble tray, move the plant away from direct sun, and flush the soil periodically to remove mineral buildup.

Drooping leaves on Anthurium watermaliense usually indicate either underwatering or root rot from overwatering. Check the substrate: if it's bone dry, give the plant a thorough watering. If it's soggy, root rot may be the cause — remove the plant, trim damaged roots, and repot in fresh aroid mix. Temperature stress (below 15°C) and transplant shock can also cause temporary drooping. The plant should recover once conditions stabilize.

The most common pests are mealybugs, spider mites, thrips, and aphids. Spider mites thrive in low-humidity conditions, so maintaining high humidity helps prevent them. Treat infestations with neem oil diluted in water and sprayed on foliage. Root rot is the most common disease, caused by overwatering or poorly draining substrate. Fungal leaf spots can develop in overly wet conditions with poor air circulation. Ensure good drainage and avoid wetting the foliage when watering.

In the wild, Anthurium watermaliense is pollinated by beetles of the genus Cyclocephala. The plant uses protogynous flowering — female flowers on the spadix become receptive first, and only after they finish does the spadix produce pollen from the male flowers. This prevents self-pollination and requires cross-pollination between different plants. In cultivation, hand pollination is possible by transferring pollen between spadices at different stages of development.

Black Anthurium should be watered regularly, allowing the soil to dry out between waterings.

Black Anthurium loves a well-draining soil. Perlite and vermiculite help with drainage, while coco coir adds organic matter, so a good potting soil mix will have all three. You can improve store-bought soil by adding some perlite to it.

To ensure optimal growth, the Black Anthurium prefers bright diffused light for 6-8 hours each day. Insufficient light can result in slow growth and leaf drop, so it's important to find a well-lit location for this plant. Place it near a window, within a distance of 1 meter (3 feet), to enhance its potential for thriving.

The Black Anthurium is not in need of supplementary humidity. Most water is taken in by plants through their roots, thus soil watering is the most efficient way to provide humidity to your plants.

The Black Anthurium should be repotted either when it doubles in size or annually, whichever comes first. Providing new potting soil with all the vital nutrients annually is enough to support the growth of the plant, and thus, there is no need for fertilizer. Remember that plants derive their energy from the sun, not fertilizer.

Ploi's records do not contain confirmed information on the toxicity of this particular plant. In the event of accidental ingestion of plant material with questionable toxicity by you, a family member, or a pet, it is always a good idea to consult a healthcare professional.

During the wintertime, it's common for Black Anthurium to go dormant and their growth may slow down, so waterings should be spaced out more.