Harvest time is one of the key factors for obtaining high-quality cherry tomatoes. This parameter depends on environmental conditions and tomato variety. In plant factories with artificial lighting (PFALs), it is possible to control environmental conditions to enhance tomato production and quality. Since the ripening status of tomato fruit is correlated with cumulative temperature (CT), and the temperature inside PFALs can be easily controlled, CT could be used as an alternative method to predict tomato harvest time. In this study, three experiments were conducted to determine the optimal CT for harvesting high-quality cherry tomatoes in a PFAL. The experiments aimed to (1) evaluate the yield and quality of cherry tomatoes as affected by different harvest times based on CT (ranging from 900 to 1400 °C), (2) comparatively evaluate the yield and quality of cherry tomatoes that were still on the plant and off the plant (in storage) based on the same CT levels (i.e., 1100, 1200, and 1300 °C), and (3) investigate the fruit-cracking percentage during the ripening stage based on CT levels. The results showed that the fruit harvested at lower CTs exhibited higher hardness values, while those harvested at higher CTs had a higher sugar content. The on-the-plant treatment resulted in a higher yield and sugar content compared with the off-the-plant treatment, indicating that harvesting tomatoes early would come at the expense of a certain yield and sweetness. Moreover, the fruit-cracking percentage tended to increase with increasing CT, possibly due to the fast fruit growth rate and increased internal turgor pressure. These results indicated that producers can use CT as an index to predict the harvest time, thereby optimizing profits in cherry tomato production.

Calendula is an edible flower with highly beneficial bioactive compounds for human health. Environmental factors such as light influence flower yield and quality. Calendula is cultivated under controlled environments in plant factories with artificial lighting (PFALs), which enhance its productivity. However, electricity is the main operating cost, with fees based on the time of use in some countries. This study aimed to investigate the effects of lighting patterns on calendula growth and yield. Two varieties of calendula seedlings were cultivated in a PFAL and subjected to six different lighting patterns, i.e., 6 h/6 h, 12 h/12 h, 6 h/2 h, and 18 h/6 h (light/dark) and two continuous lighting patterns with varying light intensities (24 h-200 and 24 h-400). The results indicated that plants cultivated under the 6 h/2 h, 18 h/6 h, 24 h-200, and 24 h-400 conditions showed a more rapid appearance of the first flower bud than those cultivated under the 6 h/6 h and 12 h/12 h conditions. The number of flowers and the fresh and dried weights tended to increase with a longer photoperiod. Interestingly, the total carotenoid content (TCC) of “Citrus Orange” increased under 6 h/6 h and 12 h/12 h conditions compared with the others. For “Orange Gem”, continuous lighting (24 h) increased the total phenolic content (TPC) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity in flowers compared with the 6 h/6 h 12 h/12 h, and 6 h/2 h treatments. The energy use efficiency (EUE) under the 24 h-200 condition was the highest in terms of flower yield and secondary metabolite production. These results suggest that lighting patterns can be used to modulate the growth and flowering of calendula and to maximize EUE.

The consumption of edible flowers is gaining global popularity due to their culinary appeal, vibrant colors, and health-promoting compounds. Traditional production methods—including wild collection, open-field cultivation, and greenhouse systems—offer limited control over environmental factors, often resulting in inconsistent yield, quality, and safety. To address these limitations, plant factories with artificial lighting (PFALs) have emerged as a promising technology for producing high-quality edible flowers year-round in controlled environments. This review explores the evolution of edible flower cultivation, from conventional methods to PFALs, and highlights key environmental factors—light, temperature, and nutrient management—that influence growth, flowering, and phytochemical profiles. Special attention is given to how light intensity, spectrum, and photoperiod affect morphogenesis and metabolite accumulation, and how nutrient solution composition, particularly nitrogen form and EC levels, modulates flowering and plant health. While recent studies have demonstrated the potential of PFALs in cultivating species such as calendula, nasturtium, and marigold, research remains limited for many commercially relevant species. The review identifies current challenges, such as high operational costs and knowledge gaps in species-specific protocols, and outlines future research directions aimed at improving efficiency, optimizing quality, and expanding market viability. PFALs offer a transformative opportunity for the edible flower industry by integrating precision agriculture with consumer demand for safe, functional, and visually appealing food products.

Calendula (Calendula officinalis L.), an edible and medicinal flower, faces challenges in yield uniformity and quality stability under open-field cultivation. Plant factories with artificial lighting (PFALs) are highly controlled systems that enable year-round production, efficient resource use, and consistent crop quality, making them promising for the cultivation for calendula. To optimize calendula cultivation in PFALs, this study investigates the effects of far-red (FR) light and nutrient solution modification on calendula growth, flowering, and nutrient use efficiency (NUE). The experiment was conducted using a dwarf calendula cultivar, ‘Orange Gem’. After transplanting, seedlings were subjected to a 2 × 3 factorial design comprising white (W) and end-of-day far-red (EOD-FR) lighting, in combination with three ammonium (NH₄⁺) levels (1/3×, 1×, and 3× of the Enshi formula). The EOD-FR lighting and the increase in the NH₄⁺ level resulted in taller plants and earlier first flower appearance. The shoot fresh and dry weight, the number of flowers, and the flower yield also increased under the higher NH₄⁺ concentration, regardless of the light treatment. The 3× NH₄⁺ treatment tended to enhance the nutrient absorption, leading to the highest nutrient use efficiency (NUE) based on the flower yield. These findings suggest that the application of EOD-FR lighting and high NH₄⁺ in nutrient solution can improve calendula productivity and resource-use efficiency in PFALs.

Optimizing lighting in plant factory with artificial lighting (PFAL) is essential for balancing lettuce growth and quality. Rapid plant growth in PFAL often induces physiological disorders, especially tipburn, which is associated with calcium deficiency in newly emerging leaves. This study aimed to evaluate the effects of different proportions of green light substitutions on tipburn incidence and the growth of romaine lettuce cultivated in a PFAL. Plants were grown under different proportions of green light at a total light intensity of 200 µmol m⁻² s⁻¹, consisting of 40% (G40), 60% (G60), 80% (G80), and 100% (G100) green light. The results showed that increasing the proportion of green light significantly reduced tipburn incidence from 49% to 25%, while shoot fresh weight declined by 7% and 25% when green light substitution increased to 80% and 100%, respectively. Net CO₂ assimilation of outer leaves remained similar among G40, G60, and G80 but declined by approximately 13% under 100% green light (G100). Higher proportions of green light markedly increased calcium accumulation and chlorophyll content in the inner leaves. These results suggest that higher proportions of green light may improve the inner-leaf light environment, enhance inner-leaf physiological function, and thereby reduce tipburn incidence. Substituting 60% green light achieved a good balance between growth performance and tipburn reduction. This approach offers an effective method to mitigate tipburn and improve lettuce quality in PFALs.