Growing tropical milkweed (Asclepias curassavica) indoors extends the plant’s life, providing host material for monarch butterflies outside their natural season and protecting plants from frost. This practice allows for a continuous supply of foliage for monarch caterpillars and year-round blooms in controlled environments. Bringing these plants indoors supports their growth and productivity by circumventing harsh weather.
Essential Indoor Care Requirements
Light
Tropical milkweed needs abundant light indoors, ideally at least six hours of direct sunlight daily. A south-facing window is beneficial for maximizing natural light exposure. If natural light is limited, supplement with a grow light for healthy growth and successful blooming. Insufficient light results in leggy, stretched growth and reduced flower production.
Watering
Keep the soil consistently moist but not waterlogged, allowing the top inch to dry slightly between waterings. Factors like pot size, soil composition, and indoor humidity levels influence watering frequency. Adequate drainage holes are essential to prevent water accumulation and root issues. Water thoroughly until water drains from the bottom, then discard any excess.
Soil and Potting
Tropical milkweed thrives in a well-draining potting mix that also retains some moisture. A quality potting mix designed for flowering plants, or a blend with perlite or sand, provides necessary drainage and aeration for healthy root development. The pot must have drainage holes to prevent water retention. Choose an appropriate pot size to provide sufficient root space and avoid excessive moisture.
Temperature and Humidity
Maintain a consistent indoor temperature between 65-80°F (18-27°C), reflecting its warm-climate origins. It is sensitive to sudden temperature fluctuations and cold drafts, which can cause stress. While tropical milkweed tolerates average indoor humidity, it benefits from higher levels, ideally between 50-70%. Increase humidity by placing the pot on a pebble tray or using a room humidifier.
Fertilizing
Fertilize indoor tropical milkweed during its active growing season, typically spring and summer, to support vigorous growth and flowering. Apply a balanced, diluted liquid fertilizer with an NPK ratio such as 10-10-10 every four to six weeks. Avoid fertilizing during dormancy or low light, which can lead to nutrient buildup and potential root damage. Over-fertilization can result in excessive foliage at the expense of blooms.
Ongoing Maintenance
Pruning
Pruning tropical milkweed maintains its shape, encourages bushier growth, and promotes continuous flowering. Deadhead spent flowers to encourage new blooms. Trim leggy stems to maintain a compact form, especially for indoor plants with limited space. For perennial tropical milkweed, a significant cutback to about six inches in late fall or winter encourages a fresh flush of growth.
Repotting
Repotting becomes necessary when the plant outgrows its current container, typically indicated by roots circling the pot or stunted growth despite adequate care. The best time for repotting is at the beginning of the active growing season, usually in spring. Select a container only one size larger than the current one to prevent overwatering. Carefully remove the plant, gently loosen any circling roots, and place it in the new pot with fresh, well-draining soil mix, ensuring the plant is at the same depth as before.
Common Pests and Problems
Indoor Pests
Indoor tropical milkweed can attract common houseplant pests, with aphids being a frequent concern. Aphids are small, pear-shaped insects often found clustered on new growth and undersides of leaves, causing distorted foliage and a sticky residue called honeydew. Milkweed bugs, characterized by their orange and black markings, may also appear, though they generally cause minimal damage to the plant. For control, a strong stream of water can dislodge aphids, or insecticidal soap can be applied, ensuring thorough coverage.
Troubleshooting Common Issues
Yellowing leaves can indicate either overwatering, leading to root problems, or underwatering, where the plant lacks sufficient moisture. It can also signal a nutrient deficiency, suggesting a need for balanced fertilization during the growing season. Leggy growth, characterized by stretched stems and sparse foliage, is a direct result of insufficient light exposure. A lack of flowering often stems from inadequate light, but it can also be due to insufficient nutrients or the plant entering a natural dormancy period. Adjusting light exposure, reviewing watering practices, and providing appropriate fertilization can help resolve these common issues.