Roselle (Hybiscus sabdariffa L.) production is an opportunity for existing northeastern farmers and recent immigrants to cater to the growing communities of southeastern Asians, Africans and Central Americans who find this crop very appealing. Over 4 years, observation and replicated variety and production systems trials compared commercially available Roselle cultivars and their growth responses in three production systems (bare-ground multi-harvest, plastic mulch multi-harvest, bare-ground single harvest) in order to understand how best to grow this crop in the region. Results indicate that the commercially available cultivars Thai Red and Jamaica Cocktail will produce profitable quantities of leaves, will produce earlier and greater quantities of leaves when grown on black plastic mulch with drip irrigation, and have the potential to produce edible calyces in late August/early September, at least in southern New Jersey, without special protection to enhance earlier production.
Roselle (Hybiscus sabdariffa L.) is an important vegetable in many of the world’s tropical cuisines, especially throughout southeastern Asia, western Africa, and Central America. Most parts of the plant are used in various forms, from the leaves cooked as greens to the fleshy calyx used in soups and stews, as well as a colorant for a popular red drink in Mexico. A rapid increase of many of these ethnic groups in communities throughout the Northeast has created opportunities for both existing farmers and recent immigrants to grow this produce specifically for these new consumers.
Traditionally, young Roselle shoots and leaves are picked from each plant and it is allowed to re-sprout for multiple harvests, in contrast to current leafy greens production on commercial farms in southern New Jersey which consists of multiple plantings at much higher populations for once over harvest at a younger stage followed by immediate replanting. While observation plots at Rutgers indicated Roselle responds well to production on plastic mulch with drip irrigation, the optimal production and management system to grow Roselle greens in this region has not been determined. An additional challenge for Roselle production in the Northeast is the short frost-free season. Producing quality calyxes for consumption before a frost kills this tender tropical plant has not yet been achieved. Over 4 years, observation and replicated variety and production systems trials compared commercially available Roselle cultivars and their growth responses in three production systems (bare-ground multi-harvest, plastic mulch multi-harvest, bare-ground single harvest).
The Objectives/Performance Targets for this project included:
- Concurrent replicated production system and cultivar evaluation field trials to be conducted at the Morris Gbolo farm in Galloway Township, NJ and at the Rutgers Agricultural Research and Development Center (RAREC) – Upper Deerfield, NJ.
- Roselle plots will be monitored for insect and disease outbreaks to observe any significant or unusual pests.
- Yield potential will be determined by measurements of time to harvest; total fresh weight of leaves and shoots; and fresh weight of calyces (if possible).
- Project results will be disseminated through a variety of audience appropriate media including, potentially:
- update reports in the weekly Rutgers Plant and Pest Advisory Newsletter,
- plot observation during RAREC open house/grower twilight/industry field days,
- presentations at regional winter grower meetings, such as the Atlantic Coastal Ag Conference (NJ), or other grower conferences,
- submission for publication in an appropriate journal such as HortTechnology, and
- highlighted in an updated page for Roselle on the worldcrops.org website.
Concurrent production system and cultivar evaluation field trials were to be replicated at Morris Gbolo’s farm in Galloway Township, NJ and at the Rutgers Agricultural Research and Development Center (RAREC) – Upper Deerfield, NJ. Limited availability of seed prevented replicating the plots at the RAREC in 2011-2013, while a move to a new farm prevented Mr. Gbolo from hosting the 2014 trial.
In 2011, a smaller than planned demonstration trial was established on the Atlantic County, NJ farm operated by Mr. Morris Gbolo, to compare traditional multiple-harvested plantings on both bare ground and plastic mulched plots. Approximately 80 Roselle plants were transplanted into either a single bare ground or plastic mulched, flat-bed plot on 7/15/2011. The single row demonstration plot was planted alongside several beds of previously seeded Roselle that Mr. Gbolo had obtained from another seed source. The plots were irrigated as needed with overhead sprinklers.
A demonstration trial consisting of side-by-side 200 feet long flat beds with or without black plastic mulch and drip irrigation was established at Mr. Gbolo’s farm in 2012. Roselle var. Red Roselle/Thai Red seeds planted on 3/31/2012 in 48-count cell trays filled with commercial peat-lite mix. Seedlings were grown in a greenhouse for 8 weeks. Seedlings were transplanted by hand into the field beds on 6/12. Rows were spaced 4 feet on center and plants were placed 18 inches apart within the each row. Five sub-plots consisting of 3 plants each were randomly placed in each row to compare season-long multiple-harvesting of young leaves and shoots. The plots were irrigated as needed via drip irrigation under the plastic mulch while overhead irrigation was applied to the bare ground plots.
A full production trial was established in 2013 which included 6 planting x cultivar treatments in a split-plot (bare ground vs. plastic mulch), randomized block layout replicated five times was established the Gbolo farm. Roselle varieties Red Roselle/Thai Red and Jamaica Cocktail (Baker Creek Seeds), as well as a single rep of saved Thai Red seed supplied by a California gardener were included in this 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 but yields were not measured.
A final trial was conducted at the Rutgers Agricultural Research and Development Center – Upper Deerfield, NJ in 2014, but not at Mr. Gbolo’s because he moved to a new location and was not able to accommodate a trial this year. Roselle varieties Red Roselle/Thai Red and Jamaica Cocktail (both from Baker Creek Seeds) were direct seeded into plots 15 feet long and 5 feet wide in a 4×4 Latin Square to compare cultivars and harvest system for yield differences. A 4 feet long subplot was harvested either by complete removal of the plants followed by reseeding, or by stripping the leaves from the plants and allowing regrowth.
Due to excessive rains in August and early September (Tropical Storms Irene and Lee and other smaller storms) of 2011, plants grown in the plastic mulched bed began to succumb to root rots that eventually killed most of those plants, limiting the harvest period and overall yields.
Over 4 harvests, from early August through mid-September, 2012, there were no significant differences in yields of leaves and shoots between the bare ground and plastic mulched plots. Slightly faster growth on plastic mulched plots supported by higher first harvest yields, as well as earlier and greater abundance of flowers on the plastic mulched plots, was observed over the entire planting. However, variation across the plots did not support the apparent greater production, and over the full season, the differences between production systems were negligible.
However, the 2012 season produced a bonus when in early September, the Roselle plants in all plots began to blossom and produced the fleshy calyces that are prized by some ethnic groups, especially Mr. Gbolo’s community from Liberia.
In the 2013 trials, 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.
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 it would be done on a commercial greens farm, the yields would be slightly higher than the mulched plots.
Again in 2013, all transplanted Roselle plants began to blossom and produce fleshy calyces toward the end of August, despite the later planting date without any late season extension techniques (high/low tunnels, hot caps, etc.).
The 2014 trial produced variable results that are difficult to interpret. The first harvest of the ‘young’ greens by cutting whole plants and reseeding produced good yields, but was confounded by not separating the edible leaves from the tough, woody stems. The latter added significant weight to the yields, and made it difficult to make comparisons to the plants left whole and only stripped of the leaves and young edible shoots. Secondly, replanting those plots after the first harvest proved to be unsuccessful, due to poor germination and/or growth in the heat of early August. Seedlings were barely 4 inches tall at the second harvest date. Per comments under ‘Further Work Needed’, this trial should be repeated
Following the preliminary trial in 2011, the following observations were made:
- seed quantity and availability of named varieties are limiting factors to increasing production of Roselle, and
- Roselle var. Thai Red does not show any tolerance to root diseases and/or to being grown in wet soils, indicating raised bed production would likely improve production in poorly drained soils.
The second season’s trial in 2012 yielded the following observations:
- seed quantity and variety continue to be limiting factors to increasing production of Roselle,
- Roselle var. Thai Red grows well on both bare ground and on black plastic mulched beds producing an equivalent of 6882 and 7653 pounds of leaves and shoots per acre, respectively, 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.
2013 conclusions included:
- 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 in southern NJ without season extending techniques continued to show promise. 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 greater interest to wholesale grower-shipper, but this technique needs verification with additional research using proper field production methods.
Lessons learned from the 2014 trial were:
- to maximize leaf production, proper timing of harvest is critical. The literature indicates once over harvesting of young stems at 6, 10 and 14 weeks (leaving 3-4 inches of stems in the field to regrow, rather than replanting) will optimize yields of young tender shoots, but our once over harvest at 8 weeks produced too much hard woody stems that needed to be removed thus reducing harvest weight significantly.
- new plantings direct seeded in early August did not allow enough time to produce a harvestable crop.
- plantings direct seeding as late as July 1 still produced flower buds in early Sept indicating there is likely a photoperiod reaction initiating flowering. Further study would help determine optimum planting times to produce the best sized plants to maximize flower production.
Education & Outreach Activities and Participation Summary
A draft fact sheet on Roselle production is under final review and updating based on a thorough search of the literature, as well as the results of the 2012-2014 trials. The update will be published on the SARE-funded worldcrops.org website pending approval (http://www.worldcrops.org/crops/Roselle.cfm).
Three years of trials were summarized and presented at the 2014 Annual Meeting of the Northeast Branch of the American Society of Horticultural Science (Jan 7-8, 2014, Philadelphia, PA – powerpoint presentation available in Project Products section). The abstract for that presentation was published in HortScience as:
VanVranken, R.W., V. Marbey, and M. Gbolo. 2014.Potential for Roselle (Hibiscus sabdariffa L.) as an Alternative Vegetable Crop for Mid-Atlantic Growers. HortScience 49(9):S7. (Abstr.) archived at: http://hortsci.ashspublications.org/content/49/9/suppl/DC1
2014 Roselle trial plots were discussed and opened for observation during a grower tour of the Rutgers Agricultural Research and Development Center – Upper Deerfield held on Aug. 21. About 25 visitors viewed the plots and were offered Roselle salad to taste. Most of those who did try it liked the flavor, but some were not pleased with the sour taste.
Results of this project will also be presented in a Specialty/Ethnic/Leafy Greens and Herbs session of the State Vegetable Conference at the 2015 New Jersey Agricultural Convention and Trade Show on Tues, Feb. 3, 2015, in Atlantic City.
2012 results showed Roselle var. Thai Red grew well on both bare ground and on black plastic mulched beds producing an equivalent of 6882 (275 25-pound boxes) and 7653 (306 25-pound boxes) pounds of leaves and shoots per acre, respectively, over multiple harvests throughout the season. If an entire acre of Roselle could be marketed successfully, per Mr. Gbolo’s PYO market, it would equate to a gross income of $6882-$7653. In that production season, the yield increase would not cover the added cost of using black plastic mulch.
However, in 2013, both Roselle varieties Thai Red and Jamaican Cocktail grew even better on both bare ground and on black plastic mulched beds (averaging minimally >500 25-pound boxes/acre). While no differences were seen between cultivars, black plastic mulch provided a 70% increase in yield over bare-ground production with an equivalent of over 850 25-pound boxes (vs. ~500 boxes/acre on bare ground) of leaves and shoots which would make the black plastic investment worthwhile.
To date, the project PI is aware of only a few farmers (<5) who are growing Roselle for sale in the region. Mostly, these are ethnic farmers growing for their own community, but a couple of enterprising traditional American farmers have found a successful niches catering to ethnic consumers with Pick-Your-Own specialty crops. One key observation made during this project is that leafy greens should be offered as a compliment rather than the mainstay of such a PYO operation because there is a much greater income potential in denser crops such as eggplants, i.e. sold by weight, a container of eggplants will weigh significantly more than the same container full of leafy greens like Roselle.
Areas needing additional study
Morton (1987. Roselle. P. 281-286. In: Fruits of warm climates. J. F. Morton, Miami, FL.) describes cultivation “for herbage purposes” by direct seeding into hills 3-6 ft apart in rows 5-10 ft apart, then harvesting stems be cutting off entire plants at 6 weeks leaving 3-4 inches of stem to re-grow, followed by 2 more harvests at 4 and 8 weeks later. Then every 2 of 3 rows are removed, leaving the third row for calyx production.
Morton’s description is similar to what was proposed for this project but was never exactly developed. Bare ground, direct seeding at higher densities with cultivation similar to spinach and other greens shows potential for quicker and greater production of marketable shoots and leaves, per extrapolation of bare ground plantings in the 2013 trial. This would be of interest to wholesale grower-shippers, but definitely needs verification with additional research using proper field production methods before is can be recommended.
It also appears that production of the prized fleshy calyx of the Roselle blossom may be possible in southern NJ without season extending techniques, but it may also be possible to increase calyx production with earlier plantings under protected culture, or to produce them at cooler sites further north. However, the later planting date without any late season extension techniques (high/low tunnels, hot caps, etc.) may indicate the literature is correct in that there is an interaction with day length inducing flowering that will occur no matter how old/large the plants are. This would need further research to verify.