How to Grow and Care for Lisianthus (Prairie Gentian)

Lisianthus (Eustoma spp.) are tender perennials or biennials often grown as annuals. Also known as the native plant 'Prairie Gentian', they return yearly, from northern Mexico to Colorado and Nebraska. They grow about 1 to 3 feet tall, featuring bell-shaped flowers with flaring lobes that bloom on one or more upright stems. Flower commonly come in white, pink, purple, and cream, and occasionally yellow, apricot, rose, or red. Foliage is dark green, lance-shaped, and slightly fleshy in texture.

Lisianthus is in great demand for bridal bouquets and other special-occasion arrangements. Started with seeds, plants take up to six months to flower so most home gardeners start with commercial nursery plants and grow lisianthus as annuals.

Lisianthus Care

Lisanthus can be somewhat finicky to grow and care for but are worth the effort. They look good in mixed containers and borders and make long lasting cut flowers.

• Plant nursery grown lisianthus seedlings as annuals for best flowering in zones 7 and lower.
• Plant in organically rich soil with a neutral pH.
• Provide 6 to 8 hours of sun daily, and warm, dry conditions.
• Feed regularly with high phosphorous fertilizer.
• Deadhead consistently for repeat blooms.

Light

Plant lisianthus in full sun, where it receives six to eight hours a day. In areas with very hot summers, a little afternoon shade won't hurt but consistent light exposure is key for best flowers and foliage.

Soil

Lisianthus prefers soil rich in organic matter such as manure, compost, or leaf mold. Soil should be well-draining and not remain waterlogged, which can lead to root rot. Raised beds and containers work well.

Lisianthus flowers need a balanced soil pH between 6.5 and 7.0. Soil too acidic or alkaline causes yellowing foliage, less vigor, and fewer blooms.

Water

Provide about 1 inch of water per week to keep plants moist but not soggy allowing soil to dry out slightly in between. Overwatering leads to fungal diseases. Timing can be a challenge which makes drip irrigation a preferred method for establishing a consistent watering schedule.

Temperature and Humidity

Lisianthus is a heat-loving native plant in areas with dry days and warm summer nights. They tolerate heat and mild drought but suffer in areas with high humidity. These plants thrive in temperatures between 60°F and 75°F. and may survive temperatures as low as 28°F. when planted in the ground. Considered hardy only in zones 8 and higher, they are most often grown as annuals in lower zones.

Fertilizer

Feed lisianthus regularly with flower fertilizer that has one and a half times the amount of phosphorous as nitrogen. Apply it according to package directions throughout the plant's growing season. A constant nutrient stream is necessary to produce well-branched plants with abundant blossoms.

Types of Lisianthus

Lisianthus varieties are distinguished by color and size with most blooming in summer. New cultivars are being introduced that continue to bloom into autumn.

• 'Balboa': This variety features more than a dozen flowers per plant, all in shades of blue.
• 'Flamenco': A heat tolerant single flowered series in rose pink, white and yellow.
• 'Maurine': A semi-dwarf, heat-tolerant variety perfect for containers on your deck and patio.
• Sapphire Pink Rim': Compact (5 to 6 inches tall) with white blooms and pink edges.
• 'Echo Blue': This tall variety (up to 34 inches) has dark blue flowers and blooms from midsummer up to frost.

Pruning

Proper pruning of summer bloomers can yield a second flush of flowers in autumn. Start by cutting stems back to the basal rosette after initial bloom. Then pamper plants with regular irrigation and fertilizer and keep them free of weeds. Look for a second flowering around mid-September.

Propagating Lisianthus

In warm-winter zones where lisianthus is perennial, it is sometimes propagated by dividing the root ball in winter. You need a shovel, sharp cutting tool and trowel.

1. Begin by cutting back the stems and foliage to just above ground level.
2. Use a shovel to dig up the entire plant, keeping as many roots as possible including the long tap root.
3. Divide the root ball into sections with a sharp knife or trowel and include some greenery or buds on each section.
4. Immediately replant the pieces at the same level as in their original location and water thoroughly. New growth should begin within a few weeks.

How to Grow Lisianthus From Seed

Lisanthus grown from seed takes 5 to 6 months to reach mature flowering stage. In zones 7 and lower start seeds indoors in late fall. In zones 8 and higher seeds can be directly sown in the garden in late summer for bloom the following spring. Because germination is light and temperature dependent, it's best to sow seeds indoors for transplanting in the garden. You need trays or small pots, seed starter mix, plastic coverings, grow lights, potting soil and general purpose fertilizer. Follow these steps:

1. Fill trays or small pots with moistened seed starter.
2. Scatter seed on the soil surface. Lisianthus seeds are tiny and often sold as pellets, which are much easier to handle.
3. Cover with plastic and set trays or pots under grow lights. Provide 16 hours of light daily and temperatures between 70°F and 75°F for seeds to germinate.
4. Once they sprout, remove plastic and keep grow lights about one inch above the tops of seedlings. Maintain temperature between 60°F and 75°F, feed weekly with a general purpose fertilizer at half strength, and do not allow soil to dry out.
5. At seven or eight weeks, transplant seedlings into regular potting mix. Monitor and maintain temperature so that it does not exceed 75°F, which can cause seedlings to go into dormancy. Continue with a regular watering and fertilizing schedule.
6. At around five months plants should be around 4 inches tall and can be hardened off for transplant into the garden.
7. Plant out only after all danger of frost has passed in your growing zone.
   

Potting & Repotting Lisianthus

Shorter varieties grow well in containers filled with ordinary potting medium. Colors combine well in mixed containers with dianthus, coreopsis, baby's breath, and snapdragons. In zones where they remain outdoors as perennials, plants require annual repotting, going up one pot size each time.

Plant nursery starts or plugs 3- to 4-inches apart in containers deep enough to accommodate the root ball. Taller varieties require deeper pots and may require staking. Tight placement allows plants to support each other. Terra cotta and clay pots are good material choices.

Overwintering

In zones where lisianthus is perennial, cut back faded flower stalks for continued blooms and reduce feeding during winter months. Zone 7 is transitional where plants may survive if cut back to ground level and covered with a light mulch until spring.

Though challenging, some gardeners find it possible to keep potted lisianthus growing indoors and flowering through winter. The trick is giving them enough bright light, controlled temperatures, and preventing common indoor pests such as mites and fungus gnats. Feed monthly with a weak diluted fertilizer.

Common Pests & Plant Diseases

Fungus gnats are a common pest of lisianthus, and first appear in the seedling stage. Larvae live beneath the soil, feed heavily on roots, and can devastate plants. Avoid overwatering and treat affected plants with a mild insecticide or neem oil. Apply neem oil in cases of spider mite infestation.

Lisianthus are susceptible to plant viruses and stem cankers. Affected plants must be removed and discarded.

How to Get Lisianthus to Bloom

Finicky about growing conditions and care, lisianthus are highly valued as cut flowers with a long vase life.

Bloom Months

Bloom periods depend on climate and variety but in most areas plants flower in June and July with some types putting out a second flush in September or October.

How Long Does Lisianthus Bloom?

Each plant produces multiple flowers. From opening of the first bud to when the last flower fades can take between two and four weeks.

What Do Lisianthus Flowers Look and Smell Like?

Lisianthus flowers can be single or double. Compact varieties are as small as 5 to 6 inches in height, while taller varieties can reach 3 feet. Blossoms are often compared to roses and peonies with multiple petals but lisianthus have no fragrance.

How to Encourage More Blooms

Regular feeding and watering along with adequate light are necessary for abundant blooms. Deadhead spent flowers to encourage more blooms.

Caring for Lisianthus After it Blooms

In growing zones where lisianthus is perennial, cut plants back to the leaves radiating around the base of the plant after the initial bloom. In zone 7, you can try cutting back and mulching to keep lisianthus alive through the colder season.

Deadheading Lisianthus Flowers

Deadhead lisianthus flowers by cutting flower stems at the point where they emerge from two sets of leaves.

Common Problems With Lisianthus

Lack of full flowering is the most common problem but several other issues make lisianthus challenging to grow.

Plants Topple Over

Long stems are often too thin to support double-bloom varieties. Look for grow-through support rings or grids and other decorative stakes.

Cut Flowers Don't Last

Lisianthus can last up to four weeks as cut flowers. Harvest early in the day using sharp scissors to cut just above the basal leaves. Remove leaves below the waterline and trim stem bottoms before placing in the vase. Refresh water every two to three days.