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Current nitrogen (N) fertilizer recommendations for landscape-grown ornamentals are based on limited research. The objective of this research was to evaluate plant response of selected warm- and cool-season annuals to N fertilizer applied at five rates in the landscape. Three warm-season annual species [‘Profusion Cherry’ zinnia (Zinnia elegans ×angustifolia), ‘Cora White’ vinca (Catharanthus roseus), and ‘Golden Globe’ melampodium (Melampodium divaricatum)] and three cool-season annual species [‘Telstar Crimson’ dianthus (Dianthus chinensis), ‘Delta Pure Violet’ pansy (Viola wittrockiana), and ‘Montego Yellow’ snapdragon (Antirrhinum majus)] were transplanted into raised beds containing subsoil fill in U.S. Department of Agriculture (USDA) hardiness zone 9a. Slow-release N fertilizer was applied over an 18-week period at an annual N rate of 0, 2, 4, 6, and 12 lb/1000 ft². Trials were replicated a second year. Plant size index (SI), tissue chlorophyll (SPAD), and plant quality were determined every 6 weeks. Shoot biomass and tissue total Kjeldahl N (TKN) were determined at 18 weeks. Regression analysis indicated that all species required N inputs at annual rates exceeding 8 lb/1000 ft² to achieve maximum size, shoot biomass, or SPAD. However, acceptable quality plants were produced at much lower N rates. We suggest application of N fertilizer at a rate of 4 to 6 lb/1000 ft² per year to landscape-grown annuals to maintain acceptable plant quality and growth. We expect fertilization at lower rates (based on aesthetics) can reduce the amount of fertilizer applied and the potential for nutrient losses in runoff or leachate. Future research should address N fertilization needs in higher fertility soils as well as the response of other plant species.

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.

Despite inconsistent reports of nitrogen (N) fertilization response on growth of landscape-grown woody ornamentals, broad N fertilization recommendations exist in the literature. The objective of this research was to evaluate the growth and quality response of three landscape-grown woody shrub species to N fertilizer. Three ornamental shrub species, ‘Alba’ indian hawthorn (Raphiolepis indica), sweet viburnum (Viburnum odoratissimum), and ‘RADrazz’ (Knock Out™) rose (Rosa) were transplanted into field soils in central Florida (U.S. Department of Agriculture hardiness zone 9a). Controlled-release N fertilizer was applied at an annual N rate of 0, 2, 4, 6, and 12 lb/1000 ft² for 100 weeks. Plant size index measurements, SPAD readings (a measure of greenness), and visual quality ratings were completed every month through 52 weeks after planting (WAP) and then every 3 months through 100 WAP. Plant tissue total Kjeldahl N (TKN) concentrations and shoot biomass were measured at 100 WAP. Results of regression analysis indicated little to no plant response (size index, biomass, SPAD) to N fertilizer rate. Shrub quality was acceptable for all species through 76 WAP regardless of the N fertilization rate. However, quality of rose and sweet viburnum fertilized with N at the low rates (<2 lb/1000 ft²) was less than acceptable (<3 out of 5) after 76 WAP. Results suggest that posttransplant applications of fertilizer may not increase plant growth, but that low-to-moderate levels of N fertilization (2 to 4 lb/1000 ft² per year) may help plant maintain quality postestablishment.

The survival of shrubs planted into the landscape depends on sufficient irrigation during the establishment period. Few studies have investigated the effect of irrigation frequency on the posttransplant growth of landscape shrubs. We conducted two studies in U.S. Department of Agriculture hardiness zone 10b over a 2-year period in which we compared canopy growth index (GI), root extension to canopy spread ratio, canopy dry weight, and root dry weight of shrubs irrigated at different frequencies. In the first experiment, wild coffee (Psychotria nervosa) and ‘Lakeview’ orange jasmine (Murraya paniculata) shrubs were planted in Sept. 2004, Dec. 2004, Mar. 2005, and June 2005 and irrigated for 28 weeks after planting (WAP) every 2, 4, or 8 days with 3 L of water per irrigation event. In the second experiment, ‘Macafeeana’ copperleaf (Acalypha wilkesiana) and orange jasmine shrubs were planted in Sept. 2005, Dec. 2005, Mar. 2006, and June 2006 and irrigated for 28 WAP every 1, 2, or 4 days with 3 L of water per irrigation event. Canopy GI and root extension to canopy spread ratio were determined at 28, 52, and 104 WAP. The entire canopy and roots were harvested 52 and 104 WAP to determine dry weight. In Expt. 1, wild coffee and orange jasmine plants irrigated every 2 days had greater GI than plants irrigated every 8 days at 28 WAP, but GI was not different at 52 or 104 WAP. Canopy dry weight at 52 WAP was greater for plants irrigated every 2 days than every 8 days, but there was no difference at 104 WAP. There was no difference in wild coffee or orange jasmine root dry weight or root extension to canopy spread ratio among the irrigation frequencies. In Expt. 2, there were no differences in GI, canopy dry weight, root dry weight, or root extension to canopy spread ratio of copperleaf or orange jasmine irrigated everyday compared with plants irrigated every 2 or 4 days. From the data collected in these studies, it appears that irrigating wild coffee or orange jasmine every 8 days during the first 28 WAP limited canopy growth but not root development. However, after 52 WAP, rainfall events appeared to be sufficient to eliminate any initial effects from irrigation frequency. Our data suggest that wild coffee, orange jasmine, and copperleaf from 3-gal containers can be successfully established in the landscape when irrigated with 3 L of water every 4 days for the first 28 WAP.

There is limited research regarding proper fertilization rates and timing for landscape-grown herbaceous perennials. Most current nitrogen (N) fertilizer recommendations for landscape-grown perennials are based on rates for woody landscape plants or on rates for greenhouse-grown perennials. In addition, most fertilizer guidelines are defined to achieve peak growth, which may not be the best indicator of desirable plant quality. Basing fertilizer input rates on plant quality levels rather than maximum growth may result in a lower fertilizer application rate and a reduction in excess fertilizer available for leaching. The objective of this research was to evaluate the response of landscape-grown herbaceous perennials to N fertilizer applied at five rates. Five herbaceous perennials [bush daisy (Gamolepis chrysanthemoides), ‘New Gold’ lantana (Lantana ×hybrid), ‘Mystic Spires’ salvia (Salvia longispicata ×farinacea), ‘Evergreen Giant’ liriope (Liriope muscari), and ‘White Christmas’ caladium (Caladium bicolor)] were transplanted into raised landscape beds containing subsoil fill in U.S. Department of Agriculture (USDA) hardiness zone 9a. Controlled-release N fertilizer was applied at an annual N rate of 0, 2, 4, 6, and 12 lb/1000 ft² for 96 weeks. Plant size index (SI), tissue chlorophyll, and plant quality were measured every 6 weeks for 96 weeks. Flower cover was determined every 6 weeks from 42 to 96 weeks. Shoot biomass and tissue total Kjeldahl N (TKN) were measured at 96 weeks after planting (WAP). Regression analyses suggested that some species required in excess of 12 lb/1000 ft² N to reach maximum size, chlorophyll content, and shoot biomass. However, plants exhibited quality ratings of good to excellent at annual N rates of 2 to 4 lb/1000 ft² N per year. We suggest that these low to moderate levels of N fertilization (2 to 4 lb/1000 ft² N per year) will provide sufficient N to produce acceptable size and quality herbaceous perennials in the landscape.

Research supporting recommendations for fertilizer needs of landscape-grown vines and groundcovers is lacking. The objectives of our study were to (1) evaluate the quality response of selected vine and groundcover species to nitrogen (N) fertilization at five rates and (2) validate the recommended N fertilizer rates (from the initial evaluation) by monitoring quality of additional landscape-grown vine and groundcover species. Three vine species and two groundcover species were planted in west-central Florida into raised beds containing subsoil fill material in a completely randomized design. Plants were fertilized every 6 weeks with a controlled release fertilizer (20N–0P–0K–23S) at an annual N rate of 0, 2, 4, 6, or 12 lb/1000 ft². Plant aesthetic quality (0–5 scale) was assessed every 6 weeks for 30 weeks after planting. Although quality of some species increased significantly as N rate increased, all plants supplied with at least 4 lb/1000 ft² per year N fertilizer had acceptable quality ratings of 3 or better. Screening of three additional vines and four additional groundcovers fertilized with controlled release fertilizer (42N–0P–0K) at an annual N rate of 3, 5, or 7 lb/1000 ft² confirmed that fertilization with 2 to 4 lb/1000 ft² per year should be adequate to maintain acceptable vines and groundcovers grown in the landscape in west-central Florida.

Recent research suggested that the nitrogen (N) fertilizer rates needed to maintain high-quality landscape plants was lower than rates needed to grow the largest size plants. Our objective was to evaluate the effect of N fertilizer rate on the aesthetic quality of various landscape-grown annual and perennials species. Nineteen cool-season annuals, 20 warm-season annuals, and 4 perennials were planted into raised beds containing subsoil fill material in a completely randomized design in west-central Florida (U.S. Department of Agriculture hardiness zone 9b). Plants were fertilized every 12 weeks with polymer coated, slow-release N (42N–0P–0K) fertilizer at annual N rate of 3, 5, or 7 lb/1000 ft² (annuals) or 1, 3, or 5 lb/1000 ft² (perennials). Plants were rated for aesthetic quality every 6 weeks for a period of 18 weeks (annuals) or 54 weeks (perennials). For most species, quality ratings of plants fertilized with 3 lb/1000 ft² of N per year (annuals) or 1 lb/1000 ft² of N per year (perennials) were not significantly lower than plants receiving higher rates of N annually. Previously reported N fertilizer recommendations for central Florida of 2 to 4 lb/1000 ft² per year should be adequate for maintaining acceptable quality landscape-grown annual and herbaceous perennial plant species.

Growth, flowering, and survival of black-eyed susan (Rudbeckia hirta L.) from three seed sources—northern Florida (NFL), central Florida (CFL), and Texas (TEX)—were evaluated under low input conditions for one growing season at four sites in Florida. Two sites were in American Horticultural Society (AHS) Heat Zone 9 while the other two were in AHS Heat Zones 10 and 11. Growth, onset date of flowering, and number of flowers at peak flowering varied by site. With few exceptions, plants tended to reach peak flowering at about the same time. Flower diameter varied by seed source with TEX>NFL>CFL. While TEX plants were perceived as the showiest, NFL and CFL plants persisted longer under the low input conditions in Florida, and hence provided some evidence of adaptation to regional site conditions.

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.

The survival and quality of shrubs planted in the landscape from containers is dependent on irrigation to ensure the development of a healthy root system. This study determined the effect of irrigation frequency on survival, quality, canopy growth index, root to canopy spread ratio, and dry root and shoot biomass of Viburnum odoratissimum Ker-Gawl. (sweet viburnum) planted in Florida in USDA hardiness Zones 8b (Citra, FL), 9a (Balm, FL), and 10b (Ft. Lauderdale, FL). Sweet viburnum shrubs were planted into the landscape from 11.4-L (#3) containers and irrigated with 3 L every 2, 4, or 8 days. Shrubs were planted on eight dates over a 2-year period (2004 to 2006). Irrigation frequency during the 12- to 22-week irrigation period had no significant effect on sweet viburnum survival or aesthetic quality at any location. In addition, there was no irrigation effect on root spread, root to shoot biomass ratio, or root biomass for shrubs planted in Zones 8b or 9a. However, sweet viburnum irrigated every 2 days had greater canopy growth index at 28 and 104 weeks after planting than shrubs irrigated every 4 or 8 days in Zone 8b and every 8 days in Zone 9a. When planted in Zone 10b, sweet viburnum irrigated every 2 days exhibited greater growth index, shoot biomass, and root biomass than plant receiving irrigation every 4 days. Although more frequent irrigation (every 2 days) resulted in more plant growth in Zones 8b and 10b, sweet viburnum survived and grew after planting under natural rainfall conditions provided they were irrigated with 3 L of water every 8 days during establishment until roots reached the canopy edge in hardiness Zones 8b and 9a and every 4 days in hardiness Zone 10b. Subsequent supplemental irrigation (hand-watering) was only needed after irrigation was ended when plants exhibited visible signs of drought stress and there was no measurable rainfall for 30 consecutive days.