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Jaworski C.A., and S.C. Phatak. 1990. Cuphea glutinosa selections for flowering ornamental ground cover in southeast United States. p. 467-469. In: J. Janick and J.E. Simon (eds.), Advances in new crops. Timber Press, Portland, OR.

Cuphea glutinosa Selections for Flowering Ornamental Ground Cover in Southeast United States

Casimir A. Jaworski and Sharad C. Phatak


  1. INTRODUCTION
  2. EVALUATION STUDIES
  3. CONCLUSION
  4. REFERENCES
  5. Table 1
  6. Table 2

INTRODUCTION

The genus Cuphea (Lythraceae) containing about 260 species, is native in the area from Mexico through Brazil, with two species found in the eastern United States (Graham and Kleiman 1985). Much research interest has centered on cuphea because its seeds have a high content of medium chain triglycerides (MCT) (Earle et al. 1960 Graham et al. 1981, Wilson et al. 1960). The MCT include caprylic acid (C8), capric acid (C10), lauric acid (C12) and myristic acid (C14). These MCT are used in soaps and detergents, high energy foods, plasticizers, lubricants, and health foods (Thompson 1984).

An alternative use of some Cuphea spp. may be as a landscape or ornamental plant. Plants for special use in the landscape must cover bare ground, prevent erosion, add variety, tie-in different plants or add color (Georgia Cooperative Extension Service 1978, Plant Genetics and Germplasm Institute 1975). The cigar plant [C. ignea (DC)] is presently grown as an ornamental. Several selections of C. glutinosa, (Cham. & Schldl.), native to Brazil (Graham et al. 1981) have been identified with unique and desirable ornamental characteristics such as excellent ground cover and flowerings, and may have potential as ornamental ground cover for the southeastern United States. Cuphea procumbens x C. llavea hybrids have also been suggested as potential ornamental plants (Thompson et al. 1987).

EVALUATION STUDIES

Two hundred and twenty C. glutinosa plants representing 4 different introductions were transplanted to the field in May 1986. Only 25 of these plants were sill living after the 1986-87 winter and they were assigned Georgia (GA) selection numbers 1 through 25. Plants which can overwinter would have greater adaptability for a permanent landscape. The lowest temperature in the 1986-87 winter was -6°C.

Two tests were conducted on C. glutinosa during 1987-88; for environmental adaptation, and evaluation for desirable ornamental characteristics. The environmental adaptation test consisted of full sun and level soil, full sun and 30% slope, full shade (90% summer shade) under hardwood trees, and full shade (90% summer shade) under pine trees. All treatments had 10 replications of 5 cm plugs of rooted stems and seedlings of plant selection GA 16. Transplanting was on June 18, 1987. Plants were irrigated and fertilized as needed. Plants were evaluated for ground cover diameter and height, number of flowers, flower rating for attractiveness, and overall rating for growth and flowering 103 days after transplanting.

The 25 overwintering C. glutinosa selections were evaluated under full sun and level soil. Ten 5 cm plugs of rooted stems and seedlings of each Georgia selection were transplanted on June 24,1987. Plants were evaluated for ground cover diameter and height, leaf color, flower number and rating, and overall rating for growth and flowering 100 days after transplanting and were evaluated again during May and June of the following year.

C. glutinosa stems and leaves higher than 5 cm above the ground were usually killed by the cold weather while the stems and leaves next to the ground, and which completely cover the soil remained attractive and green throughout the winter. The lowest temperature in the 1987-88 winter was -7°C. The plants blossomed from early April until the first autumn freeze, about mid-November at Tifton Georgia. Flowers are light purple and have 1 to 6 petals per flower. For 6 petal flowers, the 4 ventral petals are about 0.8 x 0.2 cm while the 2 dorsal petals are 0.6 x 0.4 cm. Leaves are 1.5-2.0 x 0.5 cm. C. glutinosa survived overwintering and may be propagated by rooting of the stoloniferous shoots, by underground stolons and by seeds.

C. glutinosa will not tolerate shade, but requires full sun for optimum growth (Table 1). Growth was significantly reduced on the 30% slope, but this was probably due to weed competition. We believe that plant growth on 30% slope would have been much better if the site had been free of grass and broadleaf weeds at time of planting.

The 25 overwintering C glutinosa selections exhibited many differences in ground cover, leaf color, plant height, flowering, number of petals per flower and overall appearance (Table 2). Selection of GA 21 was based on overwintering, superior ground cover, short height superior leaf color, 6 petal flowers and superior flowering number and color. The selection of GA 23 was based on its overwintering, superior ground cover, relative tall plant fair to superior leaf color, 6 petal flowers and superior flowering number and color. GA 20 was selected for overwintering, good ground cover, medium height, fair to superior leaf color, 6 petal flowers and superior flowering. These 3 C. glutinosa selections have value as ornamental ground cover in commercial and residence landscaping. These 3 selections may also have value for erosion control and beautification along highways and as potted plants. The erosion control comes from the ground being completely covered with a dense mat of shoots near the soil.

CONCLUSION

We have made selections out of a total of 220 Cuphea glutinosa plants (GA 21, GA 23 and GA 20) with potential landscape or ornamental use for the southeast United States. These plants are adapted only to full sun and produce a large mass of purple flowers for seven months of the year. In addition to overwintering, natural propagation is by rooting, of stoloniferous shoots, by underground stolons and by seeds.

REFERENCES


Table 1. Preliminary effect of four environments on the growth and flowering of Cuphea glutinosa, plant selection GA 16, 1987.z

Plant Size Flowers Overall
Environmental treatment Diameter (cm) Height (cm) (No./225 cm2) Visual (rating)y Visual (rating)x
Full sun and level soil 52aw 13a 15a 4a 8a
Full sun, 30% slope 16b 8b 1b 2b 3b
Full shade, hardwood 3c 4c 1b 1c 1c
Full shade, pine 3c 3c 0b 1c 1c
zEvaluated September 27, 1987.
yScale: 1 to 5, with 5 as superior in flowering and attractiveness.
xScale: 1 to 10, with 10 as superior in growth and flowering.
wMean separation within columns by Waller-Duncan K ratio t test.


Table 2. Growth and flowering of Cuphea glutinosa selections under fun sun.

Fall 1987z Spring 1988
Plant Flowers Overall Plant Flowers
Georgia selection code Diameter (cm) Height (cm) Leaf colory (rating) (No./225 cm2) Visual (rating)x Visual (rating)w Height (cm)v (No./225 cm2)u (No. petals)t
GA 21 50as 11.7efghi 5.0a 28efg 2.9hi 8.7b 24.7ghi 61bc 6.0a
GA 23 51a 19.7a 3.0de 63a 4.9a 9.9a 40.5a 27g 6.0a
GA 20 42b 13.4bcde 3.1d 45c 4.2bcd 7.9cd 30.9c 42ef 6.0a
GA 1 34c 10.1ijkl 3.1d 19ijkl 3.9cde 5.8f 23.8ij 71a 6.0a
GA 2 36c 10.0ijklm 3.0de 21hij 3.8de 6.3ef 23.8ij 53d 6.0a
GA 3 36c 13.6bcd 3.0de 29ef 4.3bc 6.7e 31.0c 8hi 6.0a
GA 4 29de 12.6cdefg 2.1ij 17ijklmn 2.2kl 3.4h 27.2d 1j 1.4c
GA 5 45b 11.6fghi 4.2b 25fgh 4.2bcd 7.6d 24.0hij 51d 6.0a
GA 6 16i 8.3m 2.3hi 16jklmn 2.2kl 2.3j 22.7jk 3ij 1.8c
GA 7 20h 9.1klm 2.4gh 20hijk 2.4jk 2.4ij 25.2fgh 3ij 1.9c
GA 8 35c 12.8cdef 3.8c 33de 4.4b 7.7d 30.8c 5ij 6.0a
GA 9 22gh 10.9ghij 2.8ef 13lmn 1.9l 2.3j 26.8de 1j 1.2d
GA 10 22gh 10.2ijkl 2.6fg 15klmn 2.1kl 2.4ij 24.0hij 2ij 1.9c
GA 11 26def 12.2defgh 2.1ij 21hij 2.0kl 3.2h 26.4def 3ij 1.9c
GA 12 21h 9.3jklm 2.3hi 18ijklm 2.1kl 3.0hi 26.5def 5ij 2.1b
GA 13 30d 11.2fghi 3.9c 23ghi 3.6ef 6.1ef 25.2fgh 55cd 6.0a
GA 14 29de 10.7hijk 4.0bc 23ghi 3.6ef 6.2ef 26.2def 66ab 6.0a
GA 15 24fgh 10.1ijkl 1.9j 12n 1.81 2.4ij 26.4def 3ij 1.8c
GA 16 27def 11.6fghi 4.0bc 28efg 3.5efg 6.1ef 31.6c 44e 6.0a
GA 17 25efg 8.6lm 4.0bc 15klmn 2.7ij 5.0g 19.6l 45e 6.0a
GA 18 38c 14.6b 3.8c 37d 3.7ef 6.6e 31.9c 37f 6.0a
GA 19 23fgh 11.1fghi 2.9de 12n 2.1kl 3.3h 25.7efg 7ij 1.9c
GA 22 50a 10.0ijklm 4.9a 30ef 3.1ghi 8.2bcd 22.4k 56cd 6.0a
GA 24 52a 10.6hijk 5.0a 33de 3.3fgh 8.4bc 23.7ij 52d 6.0a
GA 25 28de 14.0bc 2.0j 54b 4.3bc 5.1g 34.4b 14h 6.0a
zOctober 2, 1987.
yScale: 1 to 5, with 5 as superior in glossy green color.
xScale: 1 to 5, with 5 as superior in flowering and attractiveness.
wScale: 1 to 10, with 10 as superior in growth and flowering.
vMay 27.
uMay 2.
tMay 13.
sMean separation within columns by Waller-Duncan K ratio t test 1% level.


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