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Seacost Marshelder (Iva imbricata Walter [Asteraceae]), a dominant Atlantic and Gulf region seashore plant, is a broad-leaved plant with a potential for building and stabilizing foredunes in the South Atlantic coast of the United States, and is recognized as an important food for beach mice. Two experiments were conducted where nursery liners were potted as stock plants and produced at four rates of fertility using Osmocote Plus (15N:9P2O5: 12K2O; 8–9 m formulation) applied as a top dress at 5.5, 11.0, 15.0, and 21.0 g/3.7-L container. The experiment was arranged as a CRD with 12 single-plant replicates of each fertility rate. Stock plant growth, cutting production, and subsequent rooting characteristics (percent rooting, root number, length) were evaluated for cuttings harvested at each of four harvests (30-day interval). Stock plant height increased as fertility rate increased for all harvests. After the first harvest, plant height did not differ among fertility rates above 5.5 g. Growth indices demonstrated that a 21.0-g application of fertilizer was necessary to increase stock plant size. The number of cuttings produced per stock plant increased linearly with increasing rate of fertility for all harvests. Cutting weight of individual cuttings increased linearly with an increase in fertilizer rate for harvests one and two, but cutting weight did not differ thereafter. The rooting response differed depending on the time of harvest. Percent rooting decreased with an increase in fertility rate for harvests two and three. Increased fertility rate did result in a decrease in root number for harvest one, but no further decrease was evident thereafter. Root length did not differ among harvest dates or fertility rates.
Seacoast marshelder (Iva imbricata) is an important coastal species contributing to building of foredunes along the Gulf of Mexico coastal regions. Hurricane activity disrupts natural regeneration, and the need for successful nursery production of sufficient plants for restoration warrants development of efficient propagation and production practices for restoration efforts. The objectives of these experiments were to investigate the effects of stock plant fertility on cutting production of seacoast marshelder and to evaluate the rooting qualities of cuttings harvested from hedged stock. Stock plants were established in 1-gal containers using a pine bark substrate amended with 6 lb/yard3 dolomitic limestone. Plants were fertilized with 15N–3.9P–10K controlled-release fertilizer (Osmocote Plus, 8- to 9-month formulation at 21 °C) applied as a top dressing at the recommended full label rate of 11 g per pot and 5.5, 15, and 21 g per pot (12 pots each) using a completely randomized design. Cuttings were collected and stock plants hedged on a regular interval [Expt. 1 (May to August) and Expt. 2 (August to November)]. Hedging of stock plants reduced height to 20 cm after each successive harvest of cuttings, but stock plant growth index increased with each successive harvest. Stock plant growth and cutting production increased as fertility rate increased, but responses were not consistent across harvest times. This trend was also true for rooting percentage and measures of root quality. Seacoast marshelder stock plant size increased as fertility increased to 15 g but not at 21 g. Inconsistencies in rooting responses across the production period were evident and were attributed to seasonal growth effects. An inverse relationship between rooting percentage and fertility rate was evident from May through July suggesting high levels of fertility should be avoided because rooting percentage, root number, and root length were reduced as fertility rate increased during that time. Conversely, higher fertilizer rates had a neutral to positive effect on rooting of seacoast marshelder during the months of August through November.
Because of its weedy nature, extensive use in the landscape, numerous cultivars, and history as an invasive plant in other countries, butterfly bush (Buddleja) was an appropriate candidate to evaluate for seed production and germination in Florida. Seed production was quantified for 14 butterfly bush taxa planted in western Florida (Milton) and central southern Florida (Fort Pierce). Each of the 14 taxa evaluated produced seed. In Fort Pierce, japanese butterfly bush (B. japonica) had the greatest capsule weight and `Gloster' butterfly bush (B. lindleyana) had the second greatest capsule weight as compared to other taxa. In Milton, `Gloster' had the greatest capsule weight and japanese butterfly bush and `Nanho Alba' butterfly bush (B. davidii var.nanhoensis) had the second greatest capsule weights as compared to other taxa. The shape and number of seed capsules per infructescence varied with cultivar. Seeds were cleaned and germinated in germination boxes with and without light at 20/10, 25/15, 30/20 and 35/25 °C (68.0/50.0, 77.0/59.0, 86.0/68.0 and 95.0/77.0 °F). Regardless of temperature or cultivar, light was required for germination. At each temperature, `Nanho Blue' butterfly bush (B. davidii var. nanhoensis) and `Moonlight' butterfly bush (B. × weyeriana) had highest germination rates (63-74%) as compared to other taxa.
Plant growth, visual quality and flowering were assessed for 14 butterfly bush (Buddleja) taxa planted in western Florida (Milton) and central southern Florida (Fort Pierce). In both locations, `Violet Eyes' butterfly bush (B. weyeriana × B. lindleyana), `Honeycomb' butterfly bush (B. × weyeriana), `Moonlight' butterfly bush (B. × weyeriana), and `Sungold' butterfly bush (B. × weyeriana) generally had the greatest growth index and shoot dry weight of all cultivars. In Fort Pierce and Milton, flower dry weights of `White Profusion' butterfly bush (B. davidii), `Nanho Alba' butterfly bush (B. davidii var. nanhoensis), and `Dartmoor' butterfly bush (B. davidii × B. davidii var. nanhoensis) were among the highest as compared to other cultivars at each site, although in Milton, `Gloster' butterfly bush (B. lindleyana), japanese butterfly bush (B. japonica) and `Honeycomb' butterfly bush also had high flower dry weights. Peak plant performance varied by month, cultivar and location. At 12 weeks, plant form and color were above average for each cultivar with the exception of `Black Knight' butterfly bush (B. davidii), lindley's butterfly bush (B. lindleyana), and `Gloster' butterfly bush in the Fort Pierce location only. After 24 weeks at each location, visual quality was above average for `Black Knight', `Dartmoor', `Gloster', `Honeycomb', `Violet Eyes', and japanese butterfly bush. Peak flowering times varied with cultivar and location. At 24 weeks, flowering of `White Profusion', `Nanho Alba', `Nanho Blue', and `Nanho Purple' butterfly bush grown in Fort Pierce was 25% to 40% less than that of the same cultivars grown in Milton. At 24 weeks, `Dartmoor' had the most flowers in both locations, covering 75% of the plant canopy.