Lisianthus flowers have gained a reputation, somewhat unfairly, of being finicky and difficult to grow. In fact, if you just learn the needs of the lisianthus and attend to them, you will be able to successfully grow a flower that commands a high price in bridal bouquets and other special occasion flower arrangements.
Get to Know Lisianthus
Also known as prairie gentian and Texas bluebell, lisianthus plants (Eustoma grandiflorum) are part of the Gentianaceae family.
The plants will grow in all zones as an annual, but you can expect better performance in areas with mild summers. Depending on the variety, the plants will grow from six to 40 inches tall and will spread up to 14 inches.
Lisianthus flowers are most commonly available in cool tones, but you may occasionally see yellow or carmine-red flowering plants for sale. Single or double three-inch blooms (most popular with florists) grow in every variation of pink and purple, as well as white and picotee bicolors. The flowers are attractive in bud as well as in full bloom. Plants usually yield several blooms on each stem. Foliage is dark green and lance-shaped.
How to Plant Lisianthus
Although you can grow lisianthus plants from seed, they aren’t for beginners, and the plants take a very long time to mature into blooming-sized plants when they aren’t cultivated under strictly maintained greenhouse conditions.
Your best bet is to buy plants with buds or flowers already emerging, as even greenhouse growers may sometimes flub and produce plants that favor foliage over flowers.
Lisianthus falls into that small category of flowers that cannot tolerate a very acidic soil pH.
If you don’t maintain a soil pH between 6.5 and 7.0, your lisianthus plants will exhibit yellowing of the leaves and decreased vigor. If soil testing reveals an acidic soil, you can add limestone to increase the alkalinity.
Keep lisianthus plants moist, but never soggy. Overwatering encourages the development of fungal diseases.
The long stems that make lisianthus flowers so elegant in the vase can be a drawback in the garden, as the stems are often too thin to support the double bloomed varieties. Don’t let this discourage you, though, as there are so many beautiful and functional grow-through supports on the market, from nearly invisible support rings and grids to decorative willow or metal cage-like tuteurs.
Lisianthus flowers like a constant nutrient stream to produce well-branched plants with abundant blossoms. Choose a flower fertilizer with 1 ½ times the amount of potassium as nitrogen, and apply it according to package directions throughout the growing season.
Fungus gnats are one of the most common pests of lisianthus and may have traveled with the plants from early in the greenhouse stage. The flying adults aren’t the problem; the larval stage beneath the soil feed heavily on roots and will devastate your plants.
Organic gardeners can use Gnatrol, a biological agent, to control the gnats. Effective chemical controls include Pyrethrum, Diazinon, and Permethrin products.
Garden Design With Lisianthus
Lisianthus flowers are a must for your sunny cutting garden. Buy mature plants as soon as they are available to provide blooms while you wait for your cosmos and zinnia seeds to grow. Grow the dwarf varieties of lisianthus in containers for your deck and patio. The delicate appearance of lisianthus plants seems at home in the cottage garden, alongside other English classics like scented stock and delphiniums.
Lisianthus Varieties to Try
Most lisianthus plants bloom best in early summer, although an increasing number of cultivars are being introduced that continue to bloom through the hottest summer months.
- ‘Balboa’ series: Produces an average of three dozen flowers per plant in shades of blue
- ‘Flamenco’ series: Although gardeners seem to prefer the double flowers over the single flowers, the heat tolerance and ability to grow without staking makes this single blossoming type worth a try.
- ‘Maurine’ series: A semi-dwarf heat tolerant type