Hibiscus Flower Roselle Seed

Hibiscus is subtropical/tropical plant, perennial in nature, but typically grown as an annual, and it needs a considerable run of hot days bare usable calyxes and gentle early falls for substantial seed sets. The timing of hibiscus seeding is especially vital in climates with early fall frosts and cold winters. In cold hardiness zones below 9b, starting seeds early in a greenhouse or using a heating mat may be beneficial. Here in Southern California (Zone 9b), we start seedlings in April, transplant them by May, get harvestable calyxes by late July, and gather seed beginning in late October through mid-November.

Seed starting 

We always start our seeds in planting trays/cells, and then transplant. Seeds can be scarified (we gently brush them with a 150-grit sandpaper) prior to planting to improve germination. It's not necessary but it improves germination considerably. Typical germination period is 5-12 days, but experientially I’ve found seeds tend to germinate quicker than that - in some cases I’ve experienced germination in as little as three days.

Soil fertility

Amending the soil with a typical vegetable fertilizer will work fine in most cases - hibiscus seems to be quite flexible to different fertility regimes, but amending the soil with copious amounts of potassium (most especially in soils where it is lacking) increases the vigor of the plants tremendously.

Cultivation



Early growth of the plants are slow, but they really get cranking with substantial warm temperatures. Leaves are edible, harvest calyxes and peel off the immature seed pods - or use a roselle de-seeder tool.

Seed saving

Viable seed is dark brown, and is visible when the calyxes pop open. In most cases we harvest pod by pod with a micro pruner - whole plants can be harvested for seed, but will likely result in immature seed being included in the mix.

References

Ayeni, Albert, Mara Sanders, Andrew Rysanek, and Meredith Melendez. Ultra-Niche Crops Series: Roselle (Hibiscus sabdariffa L.) Production and Marketing in New Jersey. New Jersey Agricultural Experiment Station, Rutgers University, 2023. Accessed October 30, 2024. https://njaes.rutgers.edu/fs1298/.

Morton, Julia F. Roselle (Hibiscus sabdariffa L.). Purdue University Center for New Crops and Plant Products. Accessed October 30, 2024. https://hort.purdue.edu/newcrop/morton/roselle.html.