Hellebores (Helleborus spp.) erupt into bloom when most other plants lie dormant, brightening gloomy colder months with their nodding, bell-shaped flowers. They perform best outdoors but will also grow well indoors if the right conditions exist. Hellebores require relatively little hands-on care apart from regular watering and feeding, making them a hassle-free houseplant. They are highly toxic , however, and must be kept out of the reach of curious children and pets.
Climate and Temperature
Few plants tolerate cold as well as hellebores, although they perform best when daytime temperatures are between 65 and 70 degrees Fahrenheit. Most hellebore varieties grow outdoors in U.S. Department of Agriculture plant hardiness zones 4 to 8, but hardiness varies between species with the the Lenten rose (Helleborus orientalis) persisting in USDA zones 4 to 9 and the Christmas rose (Heleborus niger) surviving perennially in USDA zones 3 to 8.
Both the Lenten and Christmas rose respond well to indoor culture, but cultivars such as 'Anna's Red' (Helleborus x 'Anna's Red,' USDA zones 4 to 9) need a chilling, or vernalization, period of four to six weeks between 40 and 45 degrees F to induce blooming.
Hellebores are somewhat fussy about their growing conditions, especially when grown indoors. Choosing the right location, pot and soil will allow a hellebore to live for years rather than just blooming for a single season.
Hellebores perform best when grown in very bright, filtered light. An east-, south- or west-facing window provides the best light level, although the sunlight must be tempered with a sheer curtain or very light shade to keep the plant's leaves from burning. Direct sunlight harms hellebores, so never place them near an unshaded window.
Pot and Soil
The right pot and soil is key to growing hellebores indoors. Both Lenten and Christmas rose have a mature spread of roughly 12 to 18 inches, so select a pot at least 12 inches in diameter and 12 inches deep to provide plenty of room for their vigorous, fleshy roots. Make sure the pot has drainage holes. Hellebores thrive in neutral potting soil with fast drainage and good moisture retention. High fertility isn't necessary, but neither should the soil be very lean and sandy.
Hellebores look better and suffer fewer problems indoors if the ambient humidity is slightly higher than average. One simple and effective means of raising the humidity level immediately surrounding the plant is to place the pot on a tray of moist pebbles. Keep an eye on the tray and add water whenever the pebbles dry out completely. Misting also helps, especially in winter when heating dries out the air.
Place hellebores in a bright, unheated room for four to six weeks in early winter to vernalize them. Provide just enough water to keep the leaves from shriveling. Return the plant to its original growing location after the chilling period.
Hellebores are relatively low-maintenance plants, although their needs vary slightly throughout the year. Provide regular water year-round, keeping the soil slightly moist at all times. In winter, let the soil dry out 1 inch below the surface between waterings to prevent root problems, then resume regular watering when daytime temperatures warm up to 65 degrees.
Fertilizer is key when growing a heavy bloomer such as the hellebore. A balanced fertilizer with an NPK number of 20-20-20 will provide all the macronutrients hellebores need to perform well. Dissolve 1 1/2 teaspoons of water-soluble fertilizer in 1 gallon of water and apply 1 cup of the solution to wet soil every two to three weeks. Reduce feeding by half in winter.
Potted hellebores sometimes develop a crusty white salt buildup on their soil that must be flushed away periodically. The magnesium in a weak Epsom salts solution will help bind to the salts and pull them out. The process is simple but messy, so it's best to do it in a bathtub or outdoors. Dissolve 1 teaspoon of Epsom salts in 1 gallon of water. Slowly pour the solution into the pot, rotating it back and forth, until the liquid drains from the bottom of the pot and all the solution has been used. Repeat the process several times to completely leech the soil.