Impact of Production System and Cultivar on Yields of Roselle (Hybiscus sabdariffa) Leaves and Calyces
This study is about investigating the production of Roselle in two field treatments and comparing available cultivars for yield and taste. Enough seeds were obtained to conduct a yield trial comparing transplants grown on bare ground vs. black plastic mulch production systems, as well as observations of direct seeding into bare ground plots. Randomized split-plots were established and replicated 5 times. Yields of shoots and leaves from each plot were measured on two dates when plants were at a harvestable size. Once again, in addition to the leaves and shoots harvested, the crops blossomed and produced the prized calyces late in the Fall before the trial was terminated.While commercial suppliers of Roselle seed are still limited, Baker Creek Seed, Mansfield, MO, has expanded their offerings from only the popular Thai Red to also include Jamaican Cocktail. Seeds of both cultivars were purchased for the 2013 production trial.
Cooperating farmer Morris Gbolo also obtained a small supply of seeds of the variety Thai Red from a California gardener. In addition, he had saved a quantity of Thai Red seed purchased from Baker Creek in 2012 for his pick-your-own operation at B and B Farm in Galloway Township, NJ.
In 2013, a full production trial included 6 planting x cultivar treatments in a split-plot (bare ground vs. plastic mulch), randomized block layout replicated five times was established on the Atlantic County, NJ farm operated by Mr. Morris Gbolo. Roselle varieties Red Roselle/Thai Red and Jamaica Cocktail from Baker Creek Seeds, as well as a single rep of Thai Red saved seed supplied by a California gardener were included in this year study. Plots 5 feet wide by 15 feet long were established by laying plastic mulch over the entire plot and then removing the mulch from half of each replicated plot. Plants of each of 4 cultivar-seed source combinations (2012 BkrCrk Thai Red, CA Thai Red, 2013 BkrCrk Thai Red and 2013 BkrCrk Jamaican) were started in a poly greenhouse approximately 8 weeks before transplanting into either bare ground or plastic mulched plots (15 plants/plot). The 2013 Thai Red and Jamaican were also direct seeded into bare ground plots on the same date as transplanting. Leaves and shoots of all plants (entire plots) were harvested beginning when the plants were approximately 18 inches tall. The main stems of all plants were left to regrow for multiple harvests. In addition to multiple harvests, edible calyces were produced on all transplanted plots.
The draft fact sheet on Roselle production is under review and updating based on a thorough search of the literature conducted by research technician, Victoria Marbey, as well as the results of the 2012 and 2013 trials. The update will be published on the SARE-funded worldcrops.org website in early 2014. Ms. Marbey is also a Liberian and a graduate student at Stephenson University in Maryland. Her summer work on this project exposed her to agricultural field research, while her own background and experience provided valuable insight into uses and importance of Roselle and other African crops.
A summary of the three years of trials were submitted and approved for presentation at the 2014 Annual Meeting of the Northeast Branch of the American Society of Horticultural Science (Jan 7-8, 2014, Philadelphia, PA).
Plots were harvested by stripping all leaves and shoots from all plants in each plot on Sept 10 and Oct 25. There was a significant increase in yields of leaves and shoots in the plastic mulched plots over the bare ground plantings, especially in the second harvest which contributed to a significantly higher total yield in the plastic mulched plots. (Graph 1)
Direct seeding a single row/plot at a higher density (3 seeds/ft vs 1 transplant/ft) produced a significantly lower yield than transplants planted at the same time. However, if extrapolated to 3 rows/plot, as would be done on a commercial greens farm, the yields would be slightly higher than the mulched plots. Testing 3 rows/plot would be needed to verify this potential. (Graph 2)
Again in 2013, all transplanted Roselle plants began to blossom and produce fleshy calyces. The later planting date without any late season extension techniques (high/low tunnels, hot caps, etc.) may indicate there is an interaction with daylength and/or temperature inducing flowering that was not anticipated.
- Roselle Yield Potential – Transplants on Black Plastic Mulch vs. Bare Ground
- Roselle Yield Potential – Transplants vs. Direct Seeding (Extrapolated)
Impacts and Contributions/Outcomes
The impacts of this project following this third season are the following observations:
- Roselle varieties Thai Red and Jamaican Cocktail both grow well on both bare ground and on black plastic mulched beds. No differences were seen between cultivars, but in 2013, black plastic mulch provided a 70% increase in yield over bare-ground production with an equivalent of over 850 25-pound boxes of leaves and shoots per acre over multiple harvests throughout the season.
- Producing the prized fleshy calyx of the Roselle blossom may be possible in southern NJ without season extending techniques. It may be possible to increase calyx production with earlier planting under protected culture or using protected culture to extend the harvest period later into the fall.
- For pick-your-own, plastic mulch improves yields and provides cleaner picking conditions for customers
- Through extrapolation, bare ground, direct seeding and higher density cultivation similar to spinach and other greens shows potential for quicker and greater production of marketable shoots and leaves. This would be of interest to wholesale grower-shippers. However, this technique needs verification with additional research using proper field production methods.
Rutgers Cooperative Extension – Atlantic County
6260 Old Harding Hwy
Mays Landing, NJ 08330
Office Phone: 6096250056