Cast-iron plants require very simple maintenance: watering when the soil dries out and fertilizing for part of the year. Most mistakes that occur with these plants involve overwatering (they dislike waterlogged soil) or placing them in direct sunlight. With cast-iron plants, a fairly hands-off approach is typically best.
Light
Keep cast-iron plants away from direct sunlight, which can bleach and burn the leaves. If you’re keeping one as a houseplant, a north-facing window is ideal. Set it slightly back from windows that get strong light to avoid direct sun. When growing cast-iron plants outdoors, place them in a shady area with indirect sunlight.
Soil
Cast-iron plants tolerate a wide range of soils, as long as they have good drainage. They prefer organically rich soil with a slightly acidic to neutral soil pH. Outdoors, they can grow in sandy, loamy, and even clay soils. For container plants, simply use a standard quality potting mix.
Water
While these plants have some drought tolerance, they like a moderate amount of soil moisture. Water young cast-iron plants regularly to keep the soil lightly moist but not soggy. Soil that remains wet for too long can cause root rot. Water established plants deeply, and then let the soil dry out a few inches down before watering again. A good general rule is to water when you can stick your finger in the soil and not feel any dampness.
Temperature and Humidity
Cast-iron plants prefer temperatures between 60 and 75 degrees Fahrenheit. They are not hardy to cold, and temperatures that drop below 50 degrees Fahrenheit can damage or kill them. So if you’re growing your plant in a container outdoors, be sure to take it inside well before the threat of frost. Moreover, cast-iron plants like a moderate humidity level, but it’s not a necessity for healthy growth.
Fertilizer
Feed your cast-iron plant once a month with an all-purpose liquid fertilizer during the spring and summer months, following label instructions, or use a slow-release fertilizer in the spring. It’s not necessary to fertilize during the fall and winter months. Only apply fertilizer after watering the plant to avoid burning the roots.
Types of Cast-Iron Plants
There are several varieties of cast-iron plants, including:
‘Variegata’: This cultivar features green leaves with white stripes.‘Asahi’: This variety’s green leaves develop white tips as they grow.‘Hoshi-zora’: This plant’s name translates to starry sky, and its green leaves are speckled with yellow to white dots.‘Lennon’s Song’: The leaves on this variety have light green or yellow stripes.
Propagating Cast-Iron Plants
Cast-iron plants can be propagated by division. Not only does this give you a new plant for less than it would cost at a nursery, but division also prevents mature plants from becoming overcrowded. To start a new plant, take a piece of the rhizome (underground stem) that includes at least two leaves. Plant this piece either in a pot with fresh potting mix or directly in the ground. Keep the soil lightly moist, but ensure that it has good drainage. Also, make sure the new plant stays warm but isn’t in direct sunlight. Once you see new shoots develop, you’ll know your new cast-iron plant has developed its root system and its hardiness. Then, you can begin to treat it like an established plant.
Potting and Repotting Cast-Iron Plants
When growing cast-iron plants in containers, it’s key to use a pot with ample drainage holes. An unglazed clay container also is ideal because it will allow excess soil moisture to escape through its walls. Select a pot that’s just slightly larger than the root ball to start, as these slow-growing plants won’t outgrow their containers quickly. Once you see roots growing out of the soil, you’ll know it’s time to repot your cast-iron plant into something slightly larger. This might not happen for three to five years. Ideally, try to repot in the springtime, and select one container size up. Gently remove your plant from its old pot, and place it at the same depth in the new pot with fresh potting mix.
Common Pests
Cast-iron plants do not often succumb to pest or disease problems, especially when grown in their natural environment. As houseplants, they can be slightly susceptible to common houseplant pests, including mites and scale. Rinsing the foliage can help to dislodge the pests and control a minor infestation. For more severe infestations, consider an insecticidal soap or horticultural oil.
Common Problems With Cast-Iron Plants
Cast-iron plants have very few problems as long as they’re grown in their preferred conditions. But some common issues can arise when the environment isn’t to their liking.
Browning Tips
Brown leaf tips are commonly due to overwatering or underwatering, especially with cast-iron plants grown in containers. Always check the soil moisture before watering, and wait to water until the soil is dry a few inches down. Also, ensure that excess water is able to drain out of the container.
Leaves Turning Brown
Parts of or even entire leaves turning brown on cast-iron plants is often the result of too much sunlight. Check your plant throughout the day to make sure direct sun is never hitting it, and relocate it if necessary. Drafts indoors, especially from air-conditioning vents, and cold temperatures outdoors also can cause browning foliage. Make sure your plant is protected from temperature extremes.
