So Sweet is a medium-sized hosta and a natural mutation of Guacamole that does well in southeastern Louisiana. (Photo by Yan Chen, LSU AgCenter)

Fragrant Blue is one of a few blue hostas that can grow in southeastern Louisiana. (Photo by Yan Chen, LSU AgCenter)

News Release Distributed 07/22/15

HAMMOND, La. – Shade-loving hostas are ranked the No. 1 herbaceous perennial in the United States, and for good reason, said LSU AgCenter horticulturist Yan Chen.

“The craving for having hostas in the garden is just irresistible for Louisiana gardeners,” Chen said. “And why not? We have plenty of shade under live oaks and magnolia trees.”

More than 2,500 registered cultivars provide beautiful foliage in many colors, shapes and sizes. They come in blue, yellow, green and variegated colors with smooth, puckered, wavy, round, sword-shaped and heart-shaped leaves. Hostas can be as small as less than an inch long and as large as more than a foot-and-a-half wide, Chen said.

“You can find them in all combinations,” Chen said. “No other perennials can compete with hosta in diversity.”

The challenge with growing hostas in the Deep South is that hostas need a cold winter to go into deep dormancy so that their energy is reserved for a successful return in the spring, Chens said. And during summer, Hostas need a cool night breeze to revive them from the heat they endure during the day.

“However, our winter is often too mild and our summer nights are too humid to give them a break,” she said. After being planted in a Southern garden, many varieties that thrive in the North may do well for the first year. But they won’t continue growing as they should and will simply vanish after a winter or two.

Chen conducted a variety trial at the LSU AgCenter Hammond Research Station to evaluate more than 70 hostas from species or hybrids of H. plantaginea, H. fortunei and H. sieboldians, including selections by local growers.

She evaluated plants for growth vigor (increase in size) and visual quality during summer as well as the percentage of return in spring. The top 10 varieties selected from 2009 to 2014 are Iron Gate Delight, Fragrant Bouquet, Guacamole, Stained Glass, So Sweet, Krossa Regal, August Moon, Royal Standard, Albo Marginata and Fragrant Queen.

Most of these reliable varieties are hybrids of H. plantaginea, a species originating from Southeast Asia, and have better heat tolerance and less chilling requirements, Chen said.

“Gardeners just beginning their adventure with hostas should try these cultivars, which have established and returned reliably in our shade garden,” she said. “We also have had Cathedral Windows and Fragrant Blue in our garden for two years, and they have come back reliably this year.”

Varieties that are less successful include Blue Angel, Blue Mouse Ear, Hadspan Blue, Mini Blue, Moon River, Paradigm, Paul’s Glory, Sea Thunder, Samual Blue, Wheaton Blue, Lakeside Paisley Print and Praying Hands.

“These either grow too slowly or have problems overwintering,” Chen said. “However, you can plant them in a container in combination with other annuals and then leave the pot outdoors during the winter.”

As long as you keep the soil moist, those varieties should come back in the spring just fine, she said. This is because roots in containers experience lower temperature than those in the ground, which helps deep winter dormancy.

“In the landscape, hostas love to be planted at a location with light shade,” Chen said. “Some, such as the golden yellow ones, can tolerant full sun in the morning as long as the soil is moist.”

Because of their thick roots, hostas don’t like to stand in water. Chen suggests the best results come from planting them in a raised bed with loose, moist, well-drained soil and a lot of organic matter, such as composted cow manure.

Hostas will benefit from a slow-release complete fertilizer applied in early June and organic fertilizer such as cottonseed meal or blood meal applied in August to get ready for winter, she said.

Hostas are generally low maintenance, although they have a few problems, Chen said.

“The first is a type of small rodent, either a shrew as we have caught in our garden, or a vole, which is a little bigger than a shrew,” she said. Both burrow beneath the mulch and may chew on the plant crown. To combat these rodents, mix either sharp gravel or a slate product called VoleBloc with the soil as you fill in around the roots at planting to prevent them from burrowing around the plants.

Another problem many gardeners have with hosta is slugs and snails, which leave holes in leaves. “Using pine straw instead of bark-type mulches will help reduce this problem because snails and slugs don’t like to slide over pine needles,” Chen said. In addition, tougher or thick-leaved hosta varieties such as Halcyon and Elegans are not as attractive as soft and thin-leaf varieties.

“We are adding more cultivars to our hosta collection every year,” Chen said. “Visit our garden or website for more information.”