'Princess' and 'Prince' Napiergrass

Wayne W. Hanna
(Retired USDA-ARS), Presently: Department of Crop and Soil Sciences, University of Georgia Coastal Plain Experiment Station, Tifton , GA 31793 .

John M. Ruter
Department of Horticulture, University of Georgia Coastal Plain Experiment Station, Tifton , GA 31793 .

Additional index words. Pennisetum purpureum , ornamental grass, grass breeding

Introduction

'Princess' and 'Prince' are dwarf and semi-dwarf, respectively, purple-foliaged napiergrasses ( Pennisetum purpureum (L.) Schum.) being jointly released by the U.S. Dept. of Agriculture and University of Georgia College of Agricultural and Environmental Sciences. These grasses are perennial in USDA hardiness zones 8-10. However, they can be grown as vigorous annuals in more northern zones. These plants flower under short days, therefore, these cultivars will not produce seed where winter temperatures reach freezing (0.0C) or below.

Origin

Seeds of a two napiergrass accessions, designated Anae Roxo CNPGL, were received from CENARGEN/EMBRAPA in Brazil in April 1996. These were grown under quarantine in the greenhouse during the winter of 1996-97. These segregated for a wide variety of green and various shades of purple plants with a range of vigor. The most vigorous purple pigmented plant in each accession, given the Tifton numbers N240 and N241, were selfed. Seeds of these plants were planted in the field in 1997. The progenies from these selfed plants again segregated for color and vigor in the field. Three vigorous plants, from each accession, with different shades of purple pigment development were vegetatively propagated for further evaluation in a napiergrass maintenance nursery in 1998. In 1999, two accessions, N241-5 (dwarf) and N241-8 (semidwarf) were selected for further evaluation. In 2003, we assigned the names 'Princess' to N241-5 and 'Prince' to N241-8.

Description and Performance

In 1999, multi-plant observation plantings were made at the University of Georgia Coastal Plain Experiment Station Dairy Research Center and the National Environmentally Sound Production Agriculture Laboratory. Replicated tests were planted in 2000 at Blairsville (UDSA 6b), Griffin (USDA 7b), and Savannah (USDA 8b)(Table 1) and at Tifton (USDA 8a) in 2001 and 2003 (Tables 2, 3, and 4). All test sites except Tifton were irrigated. Plants in Blairsville and Griffin did not recover in 2001 following temperatures as low as -17ºC. Plants in Tifton and Savannah survived when exposed to low temperatures of -6ºC and -8ºC, respectively.

Height of 'Princess' ranged from 123 to 142 cm and from 65 to 126 cm , whereas, height of 'Prince' ranged from 179 to 218 cm and 94 to 200 cm for the Savannah and Tifton locations, respectively (Tables 1, 2, 3, and 4). The greater growth of both cultivars was observed in 2003 when rainfall during the growing period at Tifton was 807 mm compared to 525 and 459 mm in 2001 and 2002, respectively. The height differences between years were especially evident under the non-irrigated conditions at Tifton.

Both 'Prince' and 'Princess' are quite vigorous and can produce about 40 tillers in one year under non-irrigated conditions (Tables 2, 3, and 4) and twice that many under irrigated conditions (Table 1). Tiller numbers for both cultivars rapidly increase with age of the plant as the circumference of the base of the plant increases (Tables 1, 2, 3, and 4). Diameter of the top canopy can range from 99 to 154 cm for 'Princess' and from 138 to 338 cm for 'Prince" (Tables 1, 2, 3, and 4) depending on age and moisture conditions. 'Princess' is similar to Pennisetum setaceum 'Rubrum' for height and number of tillers under non-irrigated conditions (Table 2), but 'Princess' will produce twice as many tillers under irrigated conditions (Table 1). 'Prince' significantly exceeds 'Rubrum' in all characteristics measured (Table 1). Pennisetum setaceum 'Rubrum' is not reliably cold hardy in USDA zone 8.

'Princess' has significantly longer and narrower leaves than 'Rubrum' (Table 5). 'Prince has significantly longer leaves than 'Princess', but leaf width is similar for the two cultivars.

Both 'Prince' and 'Princess' can be easily propagated by stem cuttings (Table 6). Stem cuttings with two nodes tended to produce the most shoots, although somewhat reduced in vigor, based on three-week plant heights. One or two node cuttings produced the most shoots for 'Prince, but the two-node cuttings were more vigorous.

Initial leaves on 'Prince' emerge with a purple midrib (187B) and mottled purple/green (187C/137B) blade. Later, the leaves emerge purple (187B) from the whorls. 'Prince' has bloom (155C) on the stems, abundant trichomes (1 to 2 mm long) on the sheath, trichomes (up to 4 mm long) 12 cm up the blade margin from the collar, and sparse trichomes (1 mm long) on the adaxial leaf surface. Margins of leaf blades have prominent trichomes (0.2 mm long). The abaxial leaf surface is smooth. Leaf color best fit the greyed-purple group 187B (Royal Horticultural Society).

Initial leaves on 'Princess' emerge green (137B) with purple (187D) margins and purple midrib (187C). The lower blade rapidly become mottled purple/green (187D/137B) and then emerge purple (187C) from the whorl. Stems of 'Princess' have bloom (155C) on the stems, trichomes (0.5 to 1 mm long) on the leaf sheath, trichomes (3 mm long) 5 cm up the margin of the blade from the collar, and sparse trichomes (less than 1 mm long) on the adaxial surface of leaf blade. Leaf margins have inconspicuous trichomes, and the abaxial surface is smooth. Leaf color best fit the greyed-purple group 187B (Royal Horticultural Society).

Culture

Two or three node cuttings with foliage removed root well in 8.3 cm liner pots. Rooting percentages in excess of 90% can be expected under ideal conditions. A well drained substrate and minimal misting increases survival of cuttings. Terminal cuttings have not performed as well as nodal cuttings from the stem (J. Ruter, personal observation). Well rooted liners shifted from 8.3 cm pots to #5 (19.0 liter) containers in mid-April produced salable plants at a commercial nursery in 40 days (J. Ruter, unpublished data). After cutting back, plants were again salable after 57 days. In 19 liter containers using a pine bark-based substrate, paclobutrazol drenches were not economically feasible for reducing plant growth (J. Ruter, unpublished data). Hard pruning to control plant size results in good regrowth.

Helminthosporium leaf spot has been noted on the foliage in the field and under overhead sprinklers in container nurseries, but control has not been necessary. Two-lined spittlebug ( Prosapia bicinta (Say)) has also been noted to feed on the bases of field and container-grown plants. In the field, plants should be cut back in the late winter to remove debris that harbors spittlebugs.

Plants are not recommend for landscape use in areas where a hard freeze does not regularly occur by December 1 (USDA 9-11) since reseeding may be an issue, particularly in humid, subtropical environments.

Availability

A U.S. Plant Patent for 'Princess' and 'Prince' has been applied for on behalf of the U.S. Department of Agriculture, Agricultural Research Service. Contact the authors for more information. There are 215 and 262 three-year-old plants and 582 and 317 one-year-old plants of 'Princess' and 'Prince', respectively, in the breeder nursery at Tifton, Ga. These can be used as the initial propagation stocks.

Literature Cited

Royal Horticultural Society. 2001. RHS colour chart. The Royal Horticultural Society, London .

Table 1. Plant characteristics of purple napiergrass planted in 2000 in Savannah , GA.

Table 2. Plant characteristics of purple napiergrass planted in Tifton , GA.

Measurements taken 11-28-01 , 07-11-02
P.setaceum 'Rubrum' winterkilled during 2001-02.
¹Diameter of arching leaves at top of plant.

Table 3. Plant characteristics of purple napiergrass planted in 2001 adjacent to the Natural Products Laboratory in Tifton , GA.

Measurements taken 11-28-01 , 07-11-02 , and 08-27-03 .

Table 4. 2003 plant characteristics of purple napiergrass planted in 2003 in the RDC Field at Tifton , GA.

Measurements taken 8-27-03 .
¹Diameter of arching leaves at top of plant.

Table 5. Leaf characteristics of purple napiergrass planted in 2001, 2002 and 2003 in Tifton , GA.

^aMeasurements made 11-28-01,
^bMeasurements made 07-11-02.
^cMeasurements made 08-27-03 .

top