Allen Owings, Regina Bracy, Yan Chen and Roger Rosendale
Groundcovers continue to be popular landscape plants in the southeastern United States. The two most popular groundcovers in Louisiana are liriope and monkey grass (also called mondograss). Monkey grass is closely related to liriope.
Many new liriope and monkey grass varieties have been released by wholesale nurseries over the past 10 years. Most of these have not been tested under landscape growing conditions in the Southeast. Growers and landscapers want improvements over existing varieties in terms of growth habit, disease resistance (primarily to anthracnose fungus that causes spotting and browning of leaf blades), uniformity in sun and shade performance, and winter aesthetics.
Over the past few years, the LSU AgCenter has evaluated seven new varieties and three standard varieties grown in Louisiana for seasonal landscape performance by measuring visual quality, plant height, plant spread, flowering characteristics and disease presence. A landscape evaluation of new liriope and monkey grass varieties was initiated at the LSU AgCenter Hammond Research Station (USDA hardiness zone 8B) in fall 2007. New liriope varieties evaluated were Cleopatra, New Blue, Marc Anthony, Emerald Goddess, Super Blue and Odom’s Big Blue. A new monkey grass, Crystal Falls, also was included. Standard liriope varieties included for comparison were Big Blue, Evergreen Giant and Jeanerette. New varieties
Marc Anthony is a new release from Plant Development Services Inc. (PDSI), of Loxley, Ala. It is an improved variegated- foliage variety with new foliage originating as golden yellow and green. Foliage becomes white and green when mature. Lavender blooms peak in midsummer. It is reported to reach 16 inches tall, is recommended for USDA hardiness zones 5-9 and is recommended for full sun to partial shade.
Cleopatra, another new release from PDSI, is a clumping liriope with foliage spreading up to 15 inches. In midsummer, lovely lavender spikes rise from the dark green foliage to create a wonderful accent. It is reported to reach a height of 24 inches and is recommended for USDA hardiness zones 5-9 for full sun to partially shaded locations.
New Blue, a new liriope from PDSI, sports a truly clumping growth habit and deeper foliage (dark green) and bloom (lavender) colors. New Blue is reported to reach heights of 15 inches. It is recommended for USDA hardiness zones 5-10 in full sun to partial shade.
Emerald Goddess from Rode Groundcovers in Florida is a liriope with lavender flowers. The mature height is 12-15 inches. It is faster-growing than most other varieties. It is reported to have superior resistance to common fungal and bacterial plant pathogens. Dark green foliage is retained in winter. Floral display is advertised to have better intensity, height, uniformity and duration than other liriope varieties. It is recommended for USDA hardiness zones 5-10.
Super Blue, a new selection from Big Blue, has much more vigorous growth than other Big Blue selections. This variety is available from KPS Sales, Apopka. Fla.
Other liriope varieties included in this study are Jeanerette (a commonly sold variety in Louisiana), Odom’s Big Blue (a new selection of Big Blue from Country Pines Nursery in Forest Hill, La.) and Big Blue (obtained from Doug Young Nursery in Forest Hill, La.). Evergreen Giant, commonly used in Louisiana landscapes, also was included. The new monkey grass included in this study was Crystal Falls from Head Ornamentals in Seneca, S.C.
Other new liriope varieties available but not included in these studies include Supergreen from PDSI and Mayan Blue from KPS Sales. Research study
One-gallon containers of these varieties were planted in late fall 2007 in a randomized design with two replications of five plants each. Spacing was 18 inches between plant centers. Beds were located in full sun in a fine sandy loam soil amended with fine pine bark. Plants were mulched to a depth of 2 inches with baled pine straw, and mulch was refreshed twice a year to maintain depth of coverage. Plants were fertilized with 12-6-6 fertilizer at the recommended rate in early spring and midsummer 2008. A drip irrigation system was used as needed to prevent drought stress. No insecticides or fungicides were applied. Weeds were controlled with selective hand removal, spot applications of the herbicide glyphosate and pre-emergent applications of the herbicide pendimethalin. All these practices were continued in the 2009 evaluation season.
Twice-monthly visual quality ratings were taken on plants January through December 2008. Visual quality ratings were based on a scale from 1 to 5 (1=dead, 2=below-average landscape performance, 3=average landscape performance, 4=above-average landscape performance, 5=superior landscape performance) using 0.5 increments. Height measurements from the soil line to the tallest plant were taken in October. Spread measurements representing the average of the widest portion of the plant canopy and the measurement perpendicular to the widest portion were taken in October. Anthracnose ratings based on a scale from 1 to 5 (1=no leaf spotting, 3=moderate leaf spotting, 5=high leaf spotting) were taken in December. Best-performing varieties
The best-performing liriope variety in the 2008 trials was Super Blue; Cleopatra, New Blue and Emerald Goddess were above-average performers. Odom’s Big Blue, Big Blue, Marc Anthony and Jeanerette did not perform as well as the other varieties tested. Evergreen Giant had below-average landscape performance because of root rot (common to this variety) most of the year. Crystal Falls monkey grass had good quality ratings in winter, spring and fall, but quality ratings in the summer were low because of sun scorch damage to the foliage. Super Blue was the tallest variety.
Anthracnose ratings indicated no disease on Super Blue, Emerald Goddess and Evergreen Giant. Slightly susceptible varieties were Odom’s Big Blue and Crystal Falls. Varieties moderately susceptible to anthracnose were Marc Anthony, Jeanerette and Cleopatra. Highly susceptible varieties at the end of 2008 were Big Blue and New Blue.
Allen Owings, Professor, Regina Bracy, Professor and Resident Coordinator, Yan Chen, Assistant Professor, and Roger Rosendale, Research Associate, Hammond Research Station, Hammond, La.
(This article was published in the winter 2010 issue of Louisiana Agriculture.)