Lisianthus have burst onto the scene relatively recently as popular potted plants. It’s probably been only in the last ten years they’ve been available at all, and really only the last five since they’ve become more widely available. Lisianthus are sold as blooming potted plants, alongside such stalwarts as kalanchoe and gloxinia. Properly grown, they feature large, delicate looking flowers in a variety of colors, and will bloom profusely from a busy plant for several months.
Although growers are still experimenting with the best ways to cultivate lisianthus, they are frequently available year-round, although they do best in the early spring months before it gets truly warm. Like other potted plants, lisianthus are not really designed to survive as permanently potted houseplants. Instead, they are frequently discarded once the bloom has faded. If you’d like to keep yours, be prepared for a somewhat difficult challenge and reduced vigor for the next season.
- Light: Lisianthus thrive in bright, indirect light. They dislike intense heat, which can actually reduce flowering, so do not expose them to harsh summer sun in July and August. In winter, more light is permissible.
- Water: During the growth season, water frequently, letting the soil dry out between waterings. Do not let them experience drought-like conditions. Plants will benefit from being misted regularly to improve humidity.
- Soil: A rich, peat-based potting soil with excellent drainage is beneficial. Poor drainage can rot their roots, so make sure the plant is never left in standing water.
- Fertilizer: Feed with a weak liquid fertilizer throughout the growing season. Cut fertilizer back to once a month or so in the winter.
Lisianthus are still new enough on the potted flower scene that few home growers have experience propagating them. They can be grown from seed, but their size can be surprising in this case: they will want to grow somewhat larger than you’re used to before flowering. They can also be grown from stem-tip cuttings from new plants. It’s best to take cuttings in the spring.
Repot in the early spring, when new growth emerges. Most people, however, do not keep lisianthus from one season to the next.
There is only one species regularly scene in the trade: L. russelianus. This plant is sometimes labeled the prairie gentian. Within this one species, growers have developed numerous cultivars in different colors, so look for the color you like best. All cultivars have the same growing requirements, so don’t treat any one plant different from others.
Lisianthus are not particularly difficult to nurse through a single growing season, but significantly more difficult to keep alive over the long term. To make the plants more attractive to indoor gardeners, most lisianthus are treated with growth retardants during nursery production. They are also pruned for maximum buds so the flower will be more impressive.
When shopping for lisianthus, look for a plant with a multitude of unopened buds so you’ll have more flowers. Remove dead and dying flowers to increase the length and intensity of the bloom. The downside here, of course, is that the plants rarely have the stamina and vigor to survive and thrive for another season. In terms of pests, lisianthus are especially susceptible to fungus gnats, which can spread fungal disorders. They are also vulnerable to mealybugs, aphids, and mites. Signs of infestation include tiny webs on plants, clumps of white "powdery" residue, or visible insects on the plant. Treat infestations as soon as possible to prevent them from spreading to the rest of your collection. As always, start with the least toxic treatment option first, only progressing to more serious chemicals if your initial efforts fail.