An exponential growth in global population is expected to reach nine billion by 2050, demanding a 70% increase in agriculture productivity, thus illustrating the impact of global crop production on the environment and the importance of achieving greater agricultural yields. Globally, the variety of high-quality microgreens is increasing through indoor farming at both small and large scales. The major concept of Controlled Environment Agriculture (CEA) seeks to provide an alternative to traditional agricultural cultivation. Microgreens have become popular in the twenty-first century as a food in the salad category that can fulfil some nutrient requirements. Microgreens are young seedlings that offer a wide spectrum of colours, flavours, and textures, and are characterised as a “functional food” due to their nutraceutical properties. Extensive research has shown that the nutrient profile of microgreens can be desirably tailored by preharvest cultivation and postharvest practices. This study provides new insight into two major categories, (i) environmental and (ii) cultural, responsible for microgreens’ growth and aims to explore the various agronomical factors involved in microgreens production. In addition, the review summarises recent studies that show these factors have a significant influence on microgreens development and nutritional composition.

Microgreens are gaining prominence for their high nutritional value, rapid growth cycle, and suitability for controlled-environment agriculture (CEA). Among key agronomic factors, seed density critically influences both yield and microbial safety, and it also impacts production cost. This study evaluated: (1) the effects of various seed densities on the yield and microbial load of cress (Lepidium sativum L.), rocket (Eruca sativa), and pea (Pisum sativum L.); and (2) the influence of supplemental UV-A radiation on the biomass, microbial load, and phytochemical profile of pea microgreens. The study found that fresh biomass increased with increasing seed density across all species up to a threshold, achieving maximum yields at 12 seeds/cm² for cress and rocket and 2 seeds/cm² for pea. However, higher seed densities were also associated with increased levels of total aerobic bacteria (TAB), Enterobacteriaceae, and fungi, which could pose an increased risk of microbial hazards concerning food safety, e.g., TAB in cress increasing from 7.04 ± 0.09 to 7.94 ± 0.17 log₁₀CFU/g as seed density increases from 6 to 14 seeds/cm². Initially white light supplemented with UV-A recorded a lower yield (11 g) compared to white light (13 g), but the final biomass was comparable under both lights, with microbial load remaining stable at ~3.8–4.2 log₁₀ CFU/g. A temporary increase in carotenoids exhibited significantly higher levels (2.00± 0.29 µg/mg DW) under white light supplemented with UV-A radiation compared to white light alone (1.48 ± 0.23 µg/mg DW). However, these increases were not maintained throughout the growing period. These results indicate that optimising seed density in these species is vital for balancing productivity and food safety, and continuous UV-A exposure did not lead to sustained higher phytochemical levels or reduced microbial load compared with white light alone.