Evaluating the Yield of Helianthus annuus Microgreens When Treated with Sodium Hypochlorite and Other Factors

Abstract

Microgreens are gaining popularity as a new superfood salad green, but little is known about the best methods for growing each type. The purpose of this study was to investigate the quality and yield of Helianthus annuus (Grey Striped Sunflower) microgreens grown hydroponically in a greenhouse. Variables included the time of soaking and sanitation the seeds, the type of root substrate, and the time to cover seeds during germination. For the experiment, the seeds were weighed and divided into three groups, which were soaked for 24 hours, 8 hours, or 0 hours. Afterward, the seeds were sown into hydroponic channels that were lined with burlap or biofelt mats as the root substrate. Insulation boards were then used to cover the seeds during germination. The channels were uncovered after three days and the seedlings were left to grow until being harvested at 7 days. To harvest, the substrate was shaken vigorously by hand to remove the seed hulls and stunted or unsprouted seeds. After cutting the microgreens, samples were measured for length to determine growth rate and were counted for the percentage of microgreens with the seed hull still attached. The microgreens and unsprouted seeds that fell during shaking were collected and weighed as well. This procedure was repeated for a second experiment, with an additional quick soak of the seeds in a 100 ppm sodium hypochlorite solution (diluted household bleach) for sanitation, to prevent mold. The cover time was increased to promote even the length of the microgreens and efficient removal of the seed hull from the cotyledons.

The results demonstrated that the type of root substrate had little effect on yield or the percentage of microgreens that fall during shaking. There was also no large distinction between the germination rates of the microgreens whose seeds were soaked for different times. In addition, mold growth was observed on all of the root substrates, except during the second trial where the seeds were sanitized before soaking, which allowed for a noticeable increase in germination rate and a decrease in mold growth. The results of these experiments show that sanitizing seeds is important for growing Grey Striped Sunflower microgreens in a hydroponic system. Soaking the seeds is not necessary, and covering the seeds during germination for several days does not help with consistent lengths or removal of the seed hulls.