Source: AUBURN UNIVERSITY submitted to
ACCELERATED FLOWERING, CHILLING REQUIREMENTS, AND GROWTH REGULATION OF HERBACEOUS PERENNIALS
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
TERMINATED
Funding Source
Reporting Frequency
Annual
Accession No.
0186273
Grant No.
(N/A)
Project No.
ALA012-030
Proposal No.
(N/A)
Multistate No.
(N/A)
Program Code
(N/A)
Project Start Date
Oct 1, 2000
Project End Date
Sep 30, 2006
Grant Year
(N/A)
Project Director
keever, G. J.
Recipient Organization
AUBURN UNIVERSITY
108 M. WHITE SMITH HALL
AUBURN,AL 36849
Performing Department
HORTICULTURE
Non Technical Summary
Herbaceous perennials are the most popular group of plants today, but there are numerous production problems limiting the availability of quality plants. This project will address various cultural and environmental limitations to the widespread availability of high quality herbaceous perennials.
Animal Health Component
85%
Research Effort Categories
Basic
15%
Applied
85%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
2042120102010%
2042120106010%
2052120102030%
2052120106050%
Goals / Objectives
Determine 1) effectiveness of night-interrupted lighting on flowering of herbaceous perennials produced outdoors in the southern U.S., 2) chilling requirements for shoot emergence and vigor in hosta, 3) potential benefits of plant growth regulators in container production and landscape performance of herbaceous perennials.
Project Methods
1) expose numerous herbaceous perennials to night-interrupted lighting outdoors in nurseries beginning 2/1, 2/15, 3/1, 3/15 or keep under natural photoperiod. Determine time to flower, flower counts,plant size and quality at first flower. 2) chill different cultivars of hosta at 4C for 2-16 weeks before forcing at 20C in greenhouses. 3)treat herbaceous perennial with different plant growth regulators, including retardants and branching agents, to control size, improve quality, and accelerate production.

Progress 10/01/00 to 09/30/06

Outputs
This project has resulted in the publication of more than 30 refereed journal articles targeting the nursery industry. More importantly, it has 1) provided nurserymen with information critical to the use of night-interrupted lighting outdoors in the accelerated production of long-day herbaceous perennials; 2) determined the chilling requirements for growth of hostas which has allowed growers and homeowners to determine southern extremes for growth of these herbaceous perennials; 3) established numerous protocols for the use of plant growth retardants and branching agents in the production of herbaceous perennials; and 4) developed a system for the accelerated production of tree-form crapemyrtles. In 2006 alone three publications with crapemyrtles demonstrated that 1) tree shelters reduced flowering, increased height growth and resulted in visibly straighter, more upright trunks with minimal lateral shoot development, all desirable attributes in tree-form crapemyrtle production; 2) coppicing resulted in visually straighter and less branched shoots which were more uniform in diameter than non-coppiced plants; and 3) reduced production light levels accelerated height growth and shoot length while reducing flowering. Caliper was reduced or not affected by production under shade, and by the end of the second season of production during which all plants were grown in full sun, plants had regained caliper lost during prior shade production.

Impacts
Progressive nurserymen are constantly looking for ways to produce crops more efficiently. Plant growth regulators (PGRs)and alternate environmental conditions and cultural practices offer growers viable options to traditional methods of producing quality plants. While hand pruning is the most widely practiced method of controlling plant size and promoting branching, PGRs like B-Nine, B-Nine/Cycocel tank mixes and Sumagic can be highly effective in controlling shoot elongation of herbaceous perennials. Benzyladenine (BA)and thidiazuron (TDZ)can greatly stimulate new shoot formation in herbaceous and woody nursery crops with minimal labor input. Growing crapemyrtles under reduced light or in tree shelters or coppicing plants during dormancy can accelerate tree-form production and improve plant quality.

Publications

  • Brooks, K.M., G.J. Keever, J.L. Sibley, and J.E. Altland. 2006. Growth response of crapemyrtle to coppicing and production light level. J. Environ. Hort. 24:149-154.
  • Brooks, K.M., G.J. Keever, J.L. Sibley, and J.E. Altland. 2006. Growth response of crapemyrtle to production light level and supplemental fertilizer. J. Environ. Hort. 24:192-196.
  • Keever, G.J., J.R. Kessler, and J.C. Stephenson. 2006. Night-interrupted lighting accelerates flowering of herbaceous perennials under nursery conditions in the southern United States. J. Environ. Hort. 24:23-28.
  • Brooks, K.M., G.J. Keever, J.E. Altland, and J.L. Sibley. 2006. Growth and flowering of crapemyrtle in response to tree shelters. J. Environ. Hort. 24:155-159.


Progress 01/01/05 to 12/31/05

Outputs
Growth retardants B-Nine (daminozide) and Cycocel (chlormequat chloride)are often applied in combination because of a reported synergism. Results from applying spray tank mixes of all combinations of 0, 2500, 5000, or 7500 B-Nine and 0, 1000, 1500, or 2000 ppm Cycocel to 'Moonbeam' coreopsis and 'Goldsturm' rudbeckia showed B-Nine alone more effective in controlling height than Cycocel or B-Nine/Cycocel tank mixes, without any phytotoxicity. Multiple applications of B-Nine/Cycocel, Sumagic (uniconazole), Cutless (fluorprimidol), and Atrimmec (dikegulac sodium) suppressed shoot elongation of common periwinkle over 30 weeks of greenhouse production. However, Atrimmec severely injured plants and Cutless suppressed shoot counts. The cytokinin benzyladenine (BA) promoted new shoot formation in hosta when applied as a crown drench or spray, crown + foliar spray, root immersion, and root + crown immersion,thus providing growers with methods of application other than the typical foliar spray. BA application number, frequency and concentration effects on shoot formation and injury in two Indian hawthorn cultivars were determined. Foliar injury increased as application number and concentration increased and interval decreased. Plants with recently broken buds were highly sensitive to BA application and injury was severe, but decreased at more advanced stages of development.

Impacts
Plant growth regulators (PGRs)offer growers alternatives to traditional methods of producing quality plants. While hand pruning is the most widely practiced method of controlling plant size and promoting branching, PGRs like B-Nine, B-Nine/Cycocel tank mixes and Sumagic can be highly effective in controlling shoot elongation of herbaceous perennials. benzyladenine (BA)can greatly stimulate new shoot formation in herbaceous and woody nursery crops with minimal labor input.

Publications

  • Keever, G.J., J.B. Clark, and T.A. Morrison. 2005. Growth regulation of Vinca minor. J. Environ. Hort. 23:14-16.
  • Keever, G.J. and J.C. Warr. 2005. Response of hosta to method and time of BA application. Plant Growth Reg. Soc. Amer. Quart. 33:4-11.
  • Oates, J.M., G.J. Keever, and J.R. Kessler, Jr. 2005. BA application frequency and concentration effects on two Indian hawthorn cultivars. J. Environ. Hort. 23:37-41.
  • Oates, J.M., G.J. Keever, and J.R. Kessler, Jr. 2005. Developmental stage influences plant response to benzyladenine. J. Environ. Hort. 23:149-152.
  • Amling, J.W., G.J. Keever, J.R. Kessler, Jr., and D.J. Eakes. 2005. Response of 'Moonbeam' coreopsis and 'Goldsturm' rudbeckia to B-Nine and Cycocel. J. Environ. Hort. 23:25-28.


Progress 01/01/04 to 12/31/04

Outputs
Chilling, while not required for Hosta plantaginea and 11 related selections, increased vigor over the 18-week evaluation period. These results will allow growers to schedule chilling to maximize plant growth. Also, we demonstrated H. plantaginea and related selections can be grown in regions where little or no natural chilling occurs. Pruning in the fall, when conditions were conducive to re-growth, increased butterfly bush's susceptibility to cold injury and death, while winter or spring pruning had no effect on cold hardiness. Crown drenches of 2000 or 3000 ppm benzyladenine (BA) applied at either division or establishment were as effective as a foliar spray of 3000 ppm BA and more effective than an untreated control in stimulating shoot formation in hosta. Multiple applications of 1250 to 2500 ppm BA increased shoot development in Indian hawthorn to such an extent little or no mechanical pruning was necessary to produce well-branched, marketable plants. Foliar injury was minimal. Mild fall temperatures followed by a sudden drop below freezing frequently leads to injury of evergreen azaleas. However, freeze tolerances varied widely among cultivars within the Robin Hill, Holly Springs, and Back Acres hybrid groups. Knowledge of how azalea cultivars respond to these conditions will aid in the selection of cultivars for large-scale nursery production in the southern U.S. where these climatic conditions are common.

Impacts
At a time when labor is an ever decreasing resource, the production of high quality woody and herbaceous nursery crops continues to be one of the most labor intensive enterprises in Alabama. The use of plant growth regulators (PGRs) as an alternative to pruning has the potential to greatly reduce labor as well as reduce or eliminate the typical 3 or more week period following pruning when plants are not actively growing. Fruit set in crapemyrtle greatly diminishes further vegetative growth, thus prolonging production. PGRs, such as Pistill, can reduce fruit set and increase vegetative growth and may shorten production. Hosta, the most popular herbaceous perennial in the U.S., is grown from Canada to the Gulf Coast, with tremendous variation in performance. An understanding of how chilling affects growth of hosta and identifying cultivars which grow vigorously with little or no chilling will provide growers and homeowners in warmer regions of the U.S. with cultivars destined to out-perform most hosta species and cultivars.

Publications

  • Warr, J.C., G.J. Keever, R.J. Kessler, Jr., D.A. Findley, and J.W. Amling. 2004. Effect of chilling duration on growth of Hosta plantaginea and 11 related cultivars. J. Environ. Hort. 22:37-40.
  • Warr, J.C., G.J. Keever, R.J. Kessler, Jr., and D.A. Findley. 2004. Time of pruning effects on cold hardiness of butterfly bush. J. Environ. Hort. 22:1-4.
  • Warr, J.C. and G.J. Keever. 2004. Response of hosta to BA crown drenches applied at division and establishment. J. Environ. Hort. 22:129-132.
  • Oates, J.M., G.J. Keever, and J.R. Kessler, Jr. 2004. BA-induced shoot formation in Indian hawthorn. J. Environ. Hort. 22:71-74.
  • Oates, J.M. and G.J. Keever. 2004. Benzyladenine-induced shoot formation in indian hawthorn (Raphiolepis indica). Comb. Proc. Intl. Plant Prop. Soc. 53:342-347.
  • Keever, G.J., C.H. Gilliam, J.W. Olive, J.T. Owen, and V.E. Jackson. 2004. Cold hardiness of Robin Hill, Holly Springs and Back Acres hybrid azalea selections. J. Amer. Rhodo. Soc. 58(1):7-11.


Progress 01/01/03 to 12/31/03

Outputs
Multiple applications of benzyladenine (BA) increased shoot counts of 'Harbour Dwarf' nandina 107 to 480% as the number of weekly applications increased. In response to 5 weekly applications of BA at 0 to 5000ppm, shoot formation increased 10-fold linearly as concentration increased. Pistill (ethephon) was applied to foliarly to 'Tuscarora' crapemyrtle to induce flower abortion and prevent fruit set during production. Flower abortion increased up to 58% as the number of application increased from 0 to 5. Pistill applications every 7, 14, or 21 days (DI)to open flowers during the first floral flush prompted abortion of 81, 51, and 18%, resp., compared to untreated plants. The same Pistill treatments during the second floral flush resulted in 96, 96, 54, and 0% abortion, resp. Plants receiving Pistill at 7, 14, and 21 DI developed 96, 108, and 2 new shoots, compared to 0 for control plants. Chilling of 8 hosta species and cultivars indicated more rapid shoot emergence and subsequent growth as chilling duration increased, but no absolute chilling requirement in any taxa. Species and cultivars varied widely in response to chilling duration. Pruning butterfly bush in the fall before plants were dormant and conditions were favorable for regrowth, increased injury and death. Pruning in winter or spring had no detrimental effects on cold hardiness.

Impacts
At a time when labor is an ever decreasing resource, the production of high quality woody and herbaceous nursery crops continues to be one of the most labor intensive enterprises in Alabama. The use of plant growth regulators (PGRs) as an alternative to pruning has the potential to greatly reduce labor as well as reduce or eliminate the typical 3 or more week period following pruning when plants are not actively growing. Fruit set in crapemyrtle greatly diminishes further vegetative growth, thus prolonging production. PGRs, such as Pistill, can reduce fruit set and increase vegetative growth and may shorten production. Hosta, the most popular herbaceous perennial in the U.S., is grown from Canada to the Gulf Coast, with tremendous variation in performance. An understanding of how chilling affects growth of hosta and identifying cultivars which grow vigorously with little or no chilling will provide growers and homeowners in warmer regions of the U.S. with cultivars destined to out-perform most hosta species and cultivars.

Publications

  • Keever, G.J. and T.A. Morrison. 2003. Multiple benzyladenine applications increase shoot formation in nandina. J. Environ. Hort. 21(3):144-147.
  • Morrison, T.A., G.J. Keever, and C.H. Gilliam. 2003. Response of Lagerstroemia x 'Tuscarora' to multiple applications of Pistill. J. Environ. Hort. 21(3):169-172.
  • Warr, J., G. Keever, J. Amling, D. Findley, and R. Kessler. 2003. Effects of chilling duration on time to shoot emergence and subsequent growth of Hosta. J. Environ. Hort. 21(3):158-161.
  • Warr, J., G. Keever, D. Findley, and R. Kessler. 2002 (publ. 2003). Time of pruning effects on cold hardiness of butterfly bush. Comb. Proc. Intl. Plant Prop. Soc. 52:566-570.


Progress 01/01/02 to 12/31/02

Outputs
Single foliar sprays of up to 4000 ppm thidiazuron (TDZ), a cotton defoliant with cytokinin properties,increased shoot formatiom in two cultivars of nandina with minimal effect on plant size or appearance. Single substrate drenches of up to 2500 ppm TDZ increased shoot formation, but were extremely phytotoxic. Atrimmec (dikegulac sodium) suppressed shoot elongation and promoted branching in Goldflame honeysuckle, a vigorous vine with a twining growth habit. Pistill (ethephon), but not Atrimmec, was effective in causing flower abortion leading to reduced fruit set and promoting branching in crapemyrtle, both beneficial responses in the production of crapemyrtle.

Impacts
At a time when labor is an ever decreasing resource the production of high quality woody and herbaceous nursery crops continues to be one of the most labor intensive enterprises in Alabama. The use of plant growth regulators (PGRs), as an alternative to pruning has the potential to greatly reduce labor, as well as reduce or eliminate the typical 3-week period following pruning when plants are not actively growing. Fruit set greatly diminishes further vegetative growth in crapemyrtle, thus prolonging the production cycle. PGRs, such as Pistill, that reduce fruit set can promote further vegetative growth and may shorten production time.

Publications

  • Keever, G.J. and D.A. Findley. 2002. Thidiazuron increases shoot formation in nandina. J. Environ. Hort. 20:24-28.
  • Bruner, L.L., G.J. Keever, J.R. Kessler, and C.H. Gilliam. 2002. Atrimmec suppresses shoot length and promotes branching of Lonicera x heckrottii 'Goldflame' (Goldflame honeysuckle). J. Environ. Hort. 20:73-76.
  • Fain, G.B., C.H. Gilliam, and G.J. Keever. 2002. Effects of Pistill and Atrimmec on production of Lagerstroemia. Proc. Intl. Plant Prop. Soc. 51:553-557.


Progress 01/01/01 to 12/31/01

Outputs
Night-interrupted lighting outdoors under nursery conditions accelerated flowering of rudbeckia and yarrow, increased flower and flower bud counts in yarrow, scabious and shasta daisy, and increased height in all species compared to plants under natural photoperiod. Benzyladenine (BA) stimulated offset formation at night temperatures of 24C or lower but not at 29C, suggesting that BA will not overcome potential adverse effects of elevated night temperature on offset production and whole-plant growth. Plant growth retardants (PGRs) that controlled Russian sage growth in the greenhouse were less effective when applied to plants grown in containers outdoors under nursery conditions. Cutless, and to a lesser extent B-Nine/Cycocel mixes, provided effective height control of canna lily during nursery production and for at least 30 days after transplanting into the landscape. Control of canna lily with Cutless was effective over a wide range of initial plant heights. Sumagic at 20-60 ppm resulted in severe stunting of canna lily and distorted foliage. B-Nine/Cycocel suppressed shoot growth of pruned, non-flowering shoots and non-pruned, partially flowering shoots of Flame honeysuckle during nursery production. Flower and fruit abortion in crapemyrtle was promoted by Pistill (ethephon) at 1000 ppm, but not by Atrimmec.

Impacts
Night-interrupted lighting outdoors in nurseries in the southern U.S. during late winter and spring promotes earlier flowering of long-day, herbaceous perennials potentially expanding the marketing window and market quality of these plants. Plant growth retardants provide a valuable tool for the successful growth of herbaceous perennials in nurseries.

Publications

  • Bruner, L.L., Keever, G.J., Kessler, J.R., and Gilliam, C.H. 2001. Growth retardant application to Canna x generalis 'Florence Vaughan'. J. Environ. Hort. 19:114-119.
  • Keever, G.J., Kessler, J.R., and Stephenson,J.C. 2001. Accelerated flowering of herbaceous perennials under nursery conditions in the southern United States. J. Environ. Hort. 19:140-144.
  • Schultz, H.C., Keever, G.J., Kessler, J.R., and Dute, R.R. 2001. BA does not reduce detrimental effects of high nighttime temperature on offset formation in hosta. J. Environ. Hort. 19:29-32.
  • Burnett, S.E., Keever, G.J., Gilliam, C.H., and Kessler, J.R. 2001. Growth regulation of Russian sage during greenhouse and nursery production. J. Environ. Hort. 19:24-28.
  • Bruner, L.L., Keever, G.J., Kessler, J.R., and Gilliam, C.H. 2001. Plant growth retardant and initial plant height affect canna lily growth and flowering. J. Environ. Hort. 19:180-183.
  • Bruner, L.L., Keever, G.J., Kessler, J.R., and Gilliam, C.H. 2001. Shoot suppression of Lonicera x heckrottii 'Goldflame' (goldflame honeysuckle) using growth retardants. J. Environ. Hort. 19:203-206.
  • Fain, G.B., Gilliam, C.H., and Keever, G.J. 2001. Response of Lagerstroemia x 'Tuscarora' to Pistill and Atrimmec. J. Environ. Hort. 19:149-152.


Progress 01/01/00 to 12/31/00

Outputs
Chilling requirements of hosta cultivars and accelerated flowering of other herbaceous perennials outdoors under night-interrupted conditions are being determined.

Impacts
(N/A)

Publications

  • No publications reported this period