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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.
Survival and subsequent growth of two beach species produced in containers of differing volume and depth were evaluated following transplant on Eglin Air Force Base, Santa Rosa Island, Fla. Rooted cuttings of gulf bluestem (Schizachyrium maritimum) were produced in four container types: 1-gal (gallon), 0.75-gal treepot, 1-qt (quart), or 164-mL Ray leach tube (RLT) containers. Root and shoot biomass of gulf bluestem harvested after 12 weeks in container production were greatest for plants grown in treepot containers and root: shoot ratio decreased as container size increased. Regardless of container size, survival of beach-planted gulf bluestem was 100%. Basal area of plants from standard gallon and treepot containers was similar 11 months after transplant and basal area for plants from treepot containers remained greater than plants from quart or RLT containers. Effect of planting zone [92, 124, 170, and 200 m landward of the Gulf of Mexico (Gulf)] on transplant survival was also evaluated for inkberry (Ilex glabra). Seedling liners of inkberry were produced in 3-gal treepot or gallon containers. Inkberry was taller when grown in 3-gal treepot containers than when grown in gallon containers. Regardless of container size, all inkberry planted 92 m from the Gulf died. Inkberry survival (>75%) when grown in 3-gal treepot containers was two to six times greater than plants grown in gallon containers (15%, 50%, 40%; 124, 170, and 200 m from Gulf, respectively). After 15 months, inkberry grown in 3-gal treepot containers remained larger with 1.5 times the mean maximum height and twice the mean canopy area compared to those grown in gallon containers.
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.
Sandhill milkweed [Asclepias humistrata (Walter)] is important for monarch butterfly [Danaus plexippus (L.)] conservation efforts, yet precise cultivation practices are largely not available. We tested the effects of three fertilizer rates and four substrate types and four container types on the performance of sandhill milkweed during greenhouse production. Seedlings fertilized with a high (0.90 g per 48-cell container) controlled-release fertilizer rate of 15N–3.9P–10.0K (15–9–12 Osmocote® Plus) had reduced performance compared with low and medium fertilizer rates (0.34 and 0.56 g per 48-cell container, respectively). Seedlings grown in large containers (∼175 mL including standard 32-cell liners and tall tree-tubes) outperformed seedlings grown in small containers (∼100 mL including standard 48-cell liners and short tree tubes). A transplant ready plant can be produced for spring within 16 weeks when seeds are sown in early January. Although sandhill milkweed seedlings can be grown under various fertilizer rates and in various containers and substrates, seedlings grown in tall tree tubes in a peat-based mix (Sunshine Mix) outperformed a nursery standard substrate and two wood fiber substrates. We recommend growing plants in a peat-based substrate within tall tree tube containers and applying a medium fertilizer rate.