Chlorosis of Liriope muscari Foliage Effected by Medium and Fertilization

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University of Florida, IFAS,
Central Florida Research and Education Center-Apopka
CFREC-Apopka Research Report RH-92-14

C.A. Conover and R.T. Poole*

Xeriscape^TM landscaping (The National Xeriscape Council Inc., P.O. Box 767936, Roswell, GA 30076-7936) is one organization's term for high quality landscapes designed to conserve water and protect the environment. Designers select site appropriate plants based on soil type, topography, local climatic conditions and intended uses of space. Plants are grouped according to sun or shade requirements and water needs, to conserve water and reduce maintenance time, soil erosion and nutrient runoff. Demand for these "environmentally friendly" landscape plans is growing and plants valued for their hardiness, drought resistance, salt tolerance and/or adaptability to many environmental conditions is expected to increase.

Liriope muscari (Decne.) (liriope or lilyturf), an attractive grass-like perennial, is a drought tolerant plant frequently included in Xeriscape^TM landscaping designs. This ground cover has deep green leathery leaves up to 18 inches long and inch wide. Plants flower for an extended period during the summer, producing white, light blue, lavender or violet blooms, depending on cultivar. Liriope grows well in shaded or sunny locations in warm and temperate climates and is propagated by division of tubers and roots.

Nurserymen growing liriope occasionally experience unexplained crop losses due to chlorosis of foliage. When several cultivars are grown together, severity of chlorosis seems to vary according to cultivar. The following experiments were conducted to determine cause of chlorosis and individual cultivar susceptibility and provide information on use of liriope in the Xeriscape^TM.

Materials and Methods

Experiment 1, a 2 x 2 x 3 factorial test, was initiated 22 April 1987 to test fluoride (F) damage on six cultivars of liriope in different potting media with different dolomite levels. Rooted Liriope muscari were transplanted from small cell packs into 6 inch nursery containers using Vergro Container Mix A (Verlite Co. Inc., Tampa, FL 33680) or a mix composed of (6:3: 1 v/v) Florida sedge peat:pine bark:builder's sand. Both media were amended with 1 lb/yd³ Micromax (Grace Sierra Co., Milpitas, CA 95035), 0 or 10 lb/yd³ dolomite and 0, 5 or 10 lb/yd³ single superphosphate which contains about 1.5 % F. Liriope were grown in full sun and temperatures ranged from 65 to 100ø F. Plants were watered three times per week. Pots were top dressed with 5 g/6 inch pot 19-6-12 Osmocote (Grace Sierra Co., Milpitas, CA 95035) on 22 April and 29 July 1987.

Severity of chlorosis was rated 24 December 1987, based the following scale: 1 = no chlorotic leaves; 2 = slight damage, salable plants; 3 = moderate chlorosis, salable but quality reduced; 4 = severe chlorosis, unsalable plants; 5 = dead plants. Plant quality was also determined on 24 December, when plants were assigned a grade using a scale of 1 = dead, 2 = poor quality, unsalable, 3 = fair quality, salable, 4 = good quality and 5 = excellent quality plant.

Experiment 2, a 3 x 3 factorial test with 5 replications per treatment, was initiated to study effects of fertilizer rate and shade level on chlorosis of several liriope cultivars. Testing began on 26 May 1988 when liners of 'Big Blue', 'Evergreen Giant' and 'Sunproof' liriope were transplanted into 6 inch nursery containers using a container mix composed of (6:3:1 v/v) Florida sedge peat:pine bark:builder's sand. Growing medium was amended with 7 lbs/yd³ dolomite and 1 lb/yd³ Micromax. Liriope were grown under 0, 30 or 60 percent shadecloth. Pots were top dressed with 3.5, 7.0 or 10.5 g/6 inch nursery pot Osmocote 196-12 (3 month release rate fertilizer) on 21 June and 15 September 1988. Potting medium moisture level was checked daily and plants were watered as needed to maintain healthy growth. On 8 December 1988 plants were rated for chlorosis severity and plant quality using the two descriptions in experiment 1.

Experiment 3 was a 4 x 3 factorial test, with 5 replications per treatment, initiated 21 February 1989 to evaluate micronutrients and fertilizer rates. Liners of 'Big Blue' liriope were potted into 6 inch nursery containers using the same mix described in experiment 2, amended with 7 lbs/yd³ dolomite and 0, 2 or 4 lbs/yd³ Micromax. Liriope were grown outdoors in full sun and watered daily. Pots were top dressed with 19-6-12 Osmocote, at rates of 5, 10, 15 or 20 g/6 inch nursery pot, on 21 February, 24 May and 14 September 1989. Plants were rated for chlorosis and plant quality as described above 24 January 1990.

Results and Conclusion

Additions of dolomite or single superphosphate to growing medium did not affect foliage chlorosis or plant quality, making it unlikely that leaf damage could be attributed to fluoride toxicity. Severity of chlorosis and plant grade of 5 of the 6 cultivars tested was affected by growing medium (Figures 1 and 2). Plants growing in Vergro Container Mix A had leaves with more chlorotic areas and received lower plant grades compared to cultivars grown in Florida sedge peat:pine bark:builder's sand. The only plant unaffected by medium, 'Evergreen Giant', had less chlorotic leaves compared to the 5 other cultivars tested. 'Evergreen Giant' was also the only salable quality cultivar produced with Vergro container Mix A.

Results from experiment 2 show foliage chlorosis was less severe and plants received higher quality grades when fertilized at 7.0 or 10.5 g/6 inch pot compared to 3.5 g/6 inch pot (Table 1). Response to shade level varied according to cultivar tested. Best quality 'Big Blue' were grown in full sun, while best quality 'Sunproof' were grown under 60% shade. 'Evergreen Giant' growth was unaffected by shade treatment and good quality 'Evergreen Giant' plants were produced under all shade levels tested.

Plant grade of 'Big Blue' liriope, grown in experiment 3, improved, and foliage developed less chlorosis when fertilizer rates were increased from 5 to 20 g/6 inch nursery pot (Table 2). Plants receiving 4 lbs/yd³ Micromax incorporated into the medium also had higher plant grades and less chlorosis compared to plants in medium containing 0 or 2 lbs/yd³.

Cause of foliage chlorosis of liriope was not determined by these experiments but results of experiment 1 suggest that fluoride is not the causal agent. Symptoms decreased when fertilizer and micronutrient rate increased, indicating that chlorosis may be due to lack of some, still undetermined, essential macro and/or micro nutrients. Foliage of 'Evergreen Giant' developed less chlorosis than other cultivars used in experiments 1 and 2 and also proved to be the most versatile cultivar tested. Acceptable quality plants were grown in both media tested in experiment 1 (Figure 2). Salable 'Evergreen Giant' were also grown in experiment 2 under full sun, 30% or 60% shade using 3.5, 7.0, or 10.5 g 19-6-12/6 inch pot (Table 1).

Figure 1. Chlorosis of 6 Liriope muscari cultivars influenced by growing medium.

Click image for larger view. [121k]
Experiment 1 was initiated on 22 April and terminated on 24 December 1987. Chlorosis severity grade was based on a scale of 1 = no chlorotic leaves, 2 = slight damage, salable plants, 3 = moderate chlorosis, salable but quality reduced, 4 = severe chlorosis, unsalable plants and 5 = dead plants.
Plants were grown in Vergro Container Mix A or a mix of 6:3:1 (v/v) Florida peat sedge:pine bark:builder's sand. Pots were top dressed with 5 g/6 inch pot 19-6-12 Osmocote fertilizer on 22 April and 29 July 1987.
Medium influence on chlorosis severity was significant at P = 0.01 for all cultivars except 'Evergreen Giant', which was not significantly affected by growing medium.

Figure 2. Plant grade of Liriope muscari cultivars influenced by growing medium.

Click image for larger view. [121k]
Experiment 1 was initiated on 22 April and terminated on 24 December 1987. Plants were graded based on a scale of 1 = dead, 2 = poor quality, unsalable, 3 = fair quality, salable, 4 = good quality and 5 = dead plants.
Plants were grown in Vergro Container Mix A or a mix of 6:3:1 (v/v) Florida sedge peat:pine bark:builder's sand.
Pots were top dressed with 5 g/6 inch pot 19-6-12 Osmocote fertilizer on 22 April and 29 July 1987.
Medium influence on plant grade was significant at P = 0.01 for all cultivars tested except 'Evergreen Giant', which was not significantly affected by growing medium.

Table 1. Influence of fertilizer rate and shade level on plant grade and chlorosis of Liriope muscari. Plants grown in 6 inch nursery containers from 26 May until 8 December 1988. Experiment 2.

^zPlants were graded based on a scale of 1 = dead, 2 = poor quality, unsalable, 3 = fair quality, salable, 4 = good quality and 5 = excellent quality plants.
^yChlorosis severity was rated based on a scale of 1 = no chlorotic leaves, 2 = slight damage, salable plants, 3 = moderate chlorosis, salable but quality reduced, 4 = severe chlorosis, unsalable plants and 5 = dead plants.
^xns, *, **: Nonsignificant, significant at P = 0.05 and P = 0.01, respectively.

Table 2. Influence of fertilizer on chlorosis and plant grade of Liriope muscari 'Big Blue'. Plants grown in 6 inch nursery containers from 21 February 1989 until 24 January 1990. Experiment 3.

^zChlorosis severity was rated based on a scale of 1 = no chlorotic leaves, 2 = slight damage, salable plants, 3 = moderate chlorosis, salable but quality reduced, 4 = severe chlorosis, unsalable plants and 5 = dead plants.
^yPlants were graded based on a scale of 1 = dead, 2 = poor quality, unsalable, 3 = fair quality, salable, 4 = good quality and 5 = excellent quality plants.
^xns, *, **: Nonsignificant, significant at P = 0.05 and P = 0.01, respectively.

*Center Director and Professor of Environmental Horticulture (retired 7/96), and Professor of Plant Physiology, respectively, University of Florida, IFAS, CFREC-Apopka, 2807 Binion Road, Apopka FL 32703-8504.

Additional Reading

1. 1.Conover, C.A. and R.T. Poole. 1985. Growth of Calathea makoyana as influenced by media,. fertilizer and irrigation. Nurseryman. Dig. 19(2):68-70.

   2.Marlatt, R.B. 1980. Mineral deficiencies and toxicities. In: Noncontagious diseases of tropical foliage plants. Univ. of Fla. IFAS, Agri. Exper. Sta. Bull. 812 pp 2-18.

   3.Poole, R.T. and C.A. Conover. 1975. Media, shade and fertilizer influence production of Areca palm, Chrysalidocarpus lutescens Wendl. Proc. Fla. State Hort. Soc. 88:603-605.

   4. Servis, R. 1992. Xeriscape^TM -the word. Ornamental Outlook 1(2):24-25.