Previous research indicated that bedding plants can be maintained in landscape soils allowed to dry to substantially less than field capacity before irrigation; however, canopy size and aesthetic quality were compromised. Continuing this research, Solenostemon scutellarioides (coleus) were grown in drainage lysimeters in an open-sided clear polyethylene-covered shelter to assess growth characteristics and landscape quality when irrigated at various managed allowable deficits. Using tensiometers, plants were irrigated back to field capacity when 30%, 40%, or 50% of plant available water within a soil was depleted. Deficits were evaluated against a control treatment of 1.25 cm daily irrigation. Additional plants were grown in a companion open field plot. Growth indices, biomass, irrigation volumes, and landscape quality ratings were recorded. No differences in final height, growth index, shoot or root dry weights, total biomass, or shoot-to-root ratios were found among treatments for either lysimeter or companion field plots. Landscape quality was comparable among treatments. However, total irrigation volume applied was significantly greater for the control treatments than deficit irrigation treatments. On average, irrigation volumes were 4.75-fold greater for daily irrigation in comparison to other treatments.
Sloane M. Scheiber and Richard C. Beeson
Sloane M. Scheiber* and Richard C. Beeson Jr.
Petunia `Midnight' were grown in drainage lysimeters in an open-sided clear polyethylene covered shelter to evaluate growth responses in response to alternative irrigation strategies. Three irrigation methods were evaluated: tensiometer-controlled automatic irrigation system, regularly scheduled irrigation utilizing an automated controller, and human perception of plant irrigation need. Drainage lysimeters (250 L) were backfilled with native sand field soil to simulate landscape conditions and managed with Best Management Practices. Following establishment, lysimeters irrigated by an automated controller were irrigated 1.3 cm daily. Tensiometer-controlled lysimeters were irrigated when plant available water (2.5 kPa to 1.5 MPa) had declined to 70% or less, and were irrigated back to field capacity. Canopy growth indices and leaf gas exchange measurements were evaluated relative to irrigation strategies. Actual evapotranspiration was calculated for each replication. Daily irrigation resulted in significantly higher assimilation rates, transpiration rates, and final shoot dry weights than the other treatments tested. Assimilation rates and transpiration rates were significantly higher for tensiometer-controlled irrigation than the human judged treatment, but no differences were found in final shoot dry mass.
Carol D. Robacker and Sloane M. Scheiber
Abelia ×grandiflora is a drought-tolerant, pest-resistant, flowering shrub that has long been used as a foundation plant. Interspecific hybridization has produced seedlings with an assortment of morphological traits, allowing for development of new cultivars with unique or improved qualities. `Raspberry Profusion' and `Lavender Mist', developed at the University of Georgia, are seedling selections of `Edward Goucher' × Abelia chinensis. `Raspberry Profusion' is a very heavy and very early bloomer. Panicles are large and showy with fragrant pink flowers and raspberry-colored sepals. Flowering begins in early May and becomes very heavy by early June. The bright-colored sepals remain on the plant throughout the summer. Summer foliage is a medium to dark green color. In a pot, `Raspberry Profusion' blooms early and heavily. `Lavender Mist' is a heavy bloomer, with clusters of fragrant lavender flowers beginning in mid-June, and continuing into autumn. Sepals are a straw-green color at the base, becoming rose at the tips. Summer foliage is gray-green. `Lavender Mist' performs well in a pot, forming a gray-green mound contrasting with the lavender blossoms scattered around the plant. Leaves on both cultivars are glossy, particularly from mid-summer through autumn. Both plants tend to be mostly deciduous in the winter. Laboratory evaluations of cold hardiness in Griffin, Ga., during Winter 2003–04 revealed a mid-winter hardiness of –18 °C to –21 °C for `Raspberry Profusion' and –15 °C to –17 °C for `Lavender Mist'. These plants develop into dense compact shrubs following pruning and establishment in the landscape.
Carol D. Robacker and Sloane M. Scheiber
Abelia ×grandiflora is a hardy shrub in the landscape, surviving heat and drought with few pest problems. However, improved cultivars with better form, the ability to retain foliage during drought, and unique flowering and foliage characteristics are in demand. `Plum Surprise' is a new cultivar of Abelia that was developed at the University of Georgia in response to these needs. `Plum Surprise' is a seedling selection from the cross `Edward Goucher' × `Francis Mason'. It forms an unusual weeping, spreading mound with fine-textured foliage. In March and April, foliage is yellow-green with scattered red/purple leaves. In late spring, the foliage becomes emerald green, changing to a lighter green throughout the summer. New stem growth is red. The most striking features of `Plum Surprise' are the fall and winter foliage color and the evergreen habit of the cultivar. As autumn progresses, the outer shoots and leaves transform to red/purple or crimson, while the inner foliage is bright emerald green. Foliage is glossy in the winter, and a deep purple or burgundy color. `Plum Surprise' is a relatively light bloomer, with flowers scattered individually or in pairs. The flowers appear white, but on close examination have a purple blush with a pale yellow throat. `Plum Surprise' is noteworthy for its heat and drought tolerance. In both the summers of 2002 and 2005, when check cultivars had lost 50% to 80% of their foliage, `Plum Surprise' exhibited little leaf drop. `Plum Surprise' performs well in a pot under nursery conditions. The foliage cascades down over the pot, making an attractive appearance in both form and color.
Sloane M. Scheiber, Jennifer Hitchcock, Sudeep Vyapari, and Lance Osborne
A series of video clips and narrated PowerPoints were developed to aid in the presentation of common horticultural techniques. To determine the most effective format for delivery of horticultural subject matter, video clips and PowerPoints were developed for three topic areas and presented to two target audience groups. Target audiences consisted of Master Gardeners (Orange and Osceola County, Fla.) and future horticulture professionals (UF Environmental Horticulture students enrolled in Landscape Plant Establishment). Upon completion of viewing both media formats, participants were asked to complete a survey. Eighty-six percent of participants completed and returned surveys. Data were sorted and analyzed for calculation of mean percent for each response sought. Results of the survey indicated that, depending upon the topic, a higher proportion (66% to 93%) of Master Gardeners preferred narrated PowerPoints in comparison to video clips. However, 60% to 70% of students preferred video clips to narrated PowerPoints. In reference to the informative nature of both videos and PowerPoints, >67% of all respondents rated both media formats between good and excellent; however, most respondents indicated new information gained was less than 40%. Factoring the costs associated with production (about $1000 per video vs. essentially no cost for narrated PowerPoints) and participant responses, narrated PowerPoints appear the best option for conveying common horticultural practices.
Erin Alvarez, Sloane M. Scheiber, and David R. Sandrock
Water use is the most important environmental issue facing the horticulture industry. As a result, many water management districts are recommending native plants for their putative low-water requirements. Numerous textbooks and trade journals claim native plants use less water than non-natives; however, previous research found no difference in water use efficiency in the field between native and non-native species. Furthermore, recommendations of ornamental grasses for use as low-maintenance and low-water-requiring landscape plants have recently escalated. This study evaluated non-native Miscanthus sinensis `Adagio' and the native Eragrostis spectabilis for irrigation requirements and drought response in a landscape setting. To simulate maximum stress, both species were planted into field plots in an open-sided, clear polyethylene covered shelter. Each species was irrigated on alternating days at 0, 0.25, 0.5, or 0.75 L for a 90-day period. Growth index and height were recorded at biweekly intervals, and final shoot and root dry masses were taken at completion of the study. Significant treatment and species effects were found for height, growth index, shoot dry weight, and biomass. Plants receiving 0.75 L of irrigation had the greatest growth, and non-irrigated plants grew significantly less. Comparisons between species found growth was greatest among Eragrostis spectabilis plants for all parameters.
Sloane M. Scheiber, Richard C. Beeson, and Heather Bass
Native plants are often promoted as an approach for water conservation in urban landscapes. However, information regarding plant water needs is based primarily upon anecdotal observations of plant performance. Direct comparisons between native and introduced species using physiological measures of plant water stress are unavailable to support or refute such recommendations. Ligustrum japonicum and Myrica cerifera, representing an introduced and native species, respectively, were transplanted into a fine sand soil to evaluate establishment rates and growth characteristics under two irrigation regimes. Each species was irrigated either daily or every 3 days and received 1.3 cm of irrigation per event for 8 months after transplant. Predawn, midday, and dusk water potentials were recorded on three consecutive days monthly, with cumulative stress intervals calculated. Height, growth indices, shoot dry mass, root dry mass and leaf area were also recorded. Water potential was significantly influenced by day of water stress level. On days without irrigation, water stress was generally greater and affected growth. Myrica irrigated daily had the greatest growth, yet plants receiving irrigation every 3 days had the least growth and greater leaf drop. In contrast, for Ligustrum there were no differences between irrigation regimes in growth responses except for growth index.
Sloane M. Scheiber, Richard C. Beeson Jr., and Sudeep Vyapari
Root ball slicing is often recommended for root-bound woody ornamentals to promote new root development during establishment in the landscape. It is a common practice among gardeners, but not necessarily landscapers, to disrupt root-bound annuals during transplant. However, little if any evidence exists for such practices. Therefore, this study evaluated the effect of root ball condition of annual bedding plants on landscape establishment and growth. Begoniasemperflorens were transplanted from 0.72-L (#1) containers into field plots in an open-sided clear polyethylene covered shelter and managed with Best Management Practices. Three root ball conditions were evaluated: non root-bound (6-week-old plants), root-bound (10-week-old plants), and root-bound with the bottom 1 cm of the root ball removed. Shoot and root dry masses and growth indices were collected weekly for 12 weeks and evaluated relative to root ball condition by linear regression analysis. Nonroot-bound plants had significantly greater biomass, growth indices, height, and root dry weights than the other treatments tested. No significant differences were found between root-bound and manipulated root-bound plants for any parameter examined. The data indicate that the practice of disrupting root-bound plants has no benefit on establishment or growth of annual bedding plants in the landscape.
Sloane M. Scheiber, Maria Paz, Edward F. Gilman, Kimberly A. Moore, Sudeep Vyapari, and Richard C. Beeson Jr.
Landscape water consumption has become a prime target for water conservation and regulation. Imposing water restrictions during landscape establishment is detrimental to plants that have not developed sufficient root systems to compensate for transpirational water losses. Generally, municipalities regulate irrigation frequency but not application rate. Application frequency affects establishment rates of shade trees, but the effects on shrub establishment are not well documented. This study evaluated three irrigation frequencies during establishment of Ilex cornuta `Burfordii Nana' and Viburnum odoratissimumin a landscape. To simulate maximum stress, both species were transplanted into field plots in an open-sided, clear polyethylene covered shelter. Each species was irrigated either every 2, 4, or 7 days, and received 9 L of water per plant per event. Predawn, midday, and dusk water potentials were recorded at 28-day intervals and cumulative stress intervals calculated. Water potentials were taken the day prior to irrigation (maximum stress day) and the day of irrigation (minimum stress). Growth indices were also recorded. As days after transplant (DAT) increased, significant declines in cumulative water stress of Ilexwere found among treatments on the day of maximum stress. The 7-day treatment declined at a faster rate than the other treatments tested. No differences were found for Viburnum. No significant differences were found on the day of irrigation as DAT increased. Differences in canopy size were not significant among treatments for either species.
Christine L. Wiese, Amy L. Shober, Edward F. Gilman, Maria Paz, Kimberly A. Moore, Sloane M. Scheiber, Meghan M. Brennan, and Sudeep Vyapari
Irrigation for establishing landscape plants is restricted to the first 60 days after planting by most water management districts in Florida, yet woody plants may require between 6 and 12 months to become established. Survival and growth of shrubs planted into landscapes depend on adequate irrigation until shrubs develop a root system capable of compensating for evapotranspiration losses. This study examined the effect of irrigation frequency on survival, quality, and growth of Ilex cornuta Lindl. & Paxt. ‘Burfordii Nana’ and Pittosporum tobira [Dryand] ‘Variegata’ planted in north (Citra, FL; USDA hardiness zone 8b) and central (Balm, FL; USDA hardiness zone 9b) Florida. Shrubs were planted into the landscape from 11.4-L (#3) containers at 3-month intervals for a total of eight planting dates over 2 years and irrigated every 2, 4, or 8 days with 3 L of water at each irrigation event. Scheduled irrigation was discontinued once roots grew to the canopy edge [12 to 22 weeks after planting (WAP)] and survival, quality, and growth were evaluated from that point through 104 WAP. Ilex cornuta ‘Burfordii Nana’ irrigated every 2 days had greater canopy growth index (52 through 88 WAP), canopy dry mass (52 and 104 WAP), and maximum root spread (20 through 64 and 88 WAP) when compared with shrubs irrigated every 8d in hardiness zone 8b. Pittosporum tobira ‘Variegata’ irrigated every 2 days had greater canopy growth index (12 through 104 WAP), maximum root spread (20 through 28 and 64 through 88 WAP), and canopy dry mass (52 and 104 WAP) when compared with shrubs irrigated every 8 days in hardiness zone 8b. However, there were no differences in shoot or root growth resulting from irrigation frequency for these shrubs planted in hardiness zone 9a. Irrigation frequency did not affect shrub survival or aesthetic quality at either location. Although more frequent irrigation (every 2 days) resulted in greater plant growth in zone 8b, the two shrub species tested survived and grew after planting in hardiness zones 8b and 9a on natural rainfall alone provided they were irrigated during establishment with 3 L every 4 to 8 days until roots reached the canopy edge. Subsequent supplemental irrigation was only needed in the following 18 months when plants showed visible signs of drought stress, which occurred when there was no measurable rainfall for 30 consecutive days.