A 31-day DLI dataset from August 2026 showing how daily light exposure changed over time, including a high-DLI period, a sharp one-day drop, and the month’s lowest value. The data helps illustrate why a single PAR reading may not represent the full daily light environment.
Read MoreZucchini (Cucurbita pepo L.) is a fast-growing greenhouse crop capable of producing a large canopy and repeated harvests in a relatively short period. That rapid growth can make environmental problems difficult to diagnose. A zucchini plant may continue producing large leaves even while fruit production is limited by low solar radiation, excessive temperature, poor pollination […]
Read MoreEggplant (Solanum melongena) is a warm-season crop with a long production cycle, a large leaf canopy and substantial demand for light and water once fruit production begins. That can make greenhouse management appear simple: more light + warm temperatures + CO₂ = more yield Research shows that the crop is more complicated than that. Greenhouse […]
Read MoreKomatsuna (Brassica rapa var. perviridis), often called Japanese mustard spinach, is a fast-growing leafy Brassica widely cultivated in Japan. Its upright leaves, relatively short crop cycle and suitability for hydroponic production make it attractive for greenhouses and plant factories. But fast growth does not mean that Komatsuna has one simple environmental recipe. Light intensity can […]
Read MoreTatsoi is a low-growing Asian leafy vegetable in the Brassica rapa group, recognizable by its dark green spoon-shaped leaves and compact rosette. Its appearance can make it seem unusually tolerant. The plant stays close to the substrate, develops thick petioles and often continues looking healthy under cool conditions. But visual appearance alone does not tell […]
Read MoreSorrel (Rumex acetosa) is a perennial leafy vegetable known for its distinctive sour flavor and ability to regrow after cutting. Because the plant is hardy and can tolerate a wide range of outdoor conditions, it is easy to assume that greenhouse sorrel needs only moderate light, water and basic climate control. Research shows a more […]
Read MoreWhat Research Actually Supports About Light, CO₂, Head Formation, Tipburn, Bolting and Water Napa cabbage, also called heading Chinese cabbage, is usually classified as Brassica rapa subsp. pekinensis. Unlike bok choy or many other leafy greens, its commercial product is not simply a collection of large leaves. The crop must develop a: compact leafy head. […]
Read MoreWhat Research Actually Supports About Light, CO₂, Water, Tipburn and Leaf Quality Bok choy, also called pak choi, is a fast-growing leafy vegetable belonging to Brassica rapa subsp. chinensis. It often appears forgiving. Large green leaves and thick petioles can develop quickly, which makes it tempting to manage bok choy with a simple recipe: more […]
Read MoreWhat Research Actually Supports About Light, Glucosinolates, CO₂, Water and Shelf Life Broccoli microgreens are young seedlings of Brassica oleracea var. italica, usually harvested around the cotyledon stage or shortly after the first true leaf begins to emerge. They are often described as easy to grow. They germinate quickly, have a short crop cycle and […]
Read MoreWhat Research Actually Supports About Light, CO₂, Tender Growth, Water and Shelf Life Pea shoots and pea microgreens are young seedlings of Pisum sativum harvested long before the plant reaches reproductive maturity. They are often described as easy crops because they: But there is no scientifically established PAR, CO₂ and VPD recipe that guarantees: tender […]
Read MoreButterhead lettuce is valued for: soft leaves, compact heads, tender texture, and high fresh-market quality. But in controlled-environment production, the biggest challenge is not simply producing enough leaf area. It is producing: high biomass without excessive tipburn. Direct research with green butterhead lettuce shows that increasing: PPFD DLI CO₂ or: temperature can accelerate growth. But […]
Read MoreRomaine lettuce (Lactuca sativa var. longifolia) is recognizable by its upright growth habit, elongated leaves and prominent midribs. Compared with loose-leaf lettuce, a mature romaine plant can look structurally robust. But that appearance does not mean romaine simply benefits from: more light more CO₂ and: drier air. Direct romaine research shows clear tradeoffs. Increasing Daily […]
Read MoreWhat Research Actually Supports About Light, CO₂, Glucosinolates, Water, Flavor and Shelf LifeMustard greens, commonly Brassica juncea, are fast-growing leafy Brassicas valued for their distinctive peppery flavor. They can be harvested as: baby leavesmature leafy greensrepeated cut greenssprouts or microgreensBut these production stages are not physiologically identical. There is no scientifically established stage-by-stage combination of: […]
Read MoreWhat Research Actually Supports About Light, Photoperiod, CO₂, Water Stress and Aroma Tarragon (Artemisia dracunculus L.) is a perennial aromatic herb valued for its narrow leaves and distinctive volatile profile. But “tarragon” is not always one identical crop. For culinary production, French tarragon is especially important. True French tarragon is normally propagated vegetatively because its […]
Read MoreTraditional PAR covers wavelengths from: 400 to 700 nm But plants do not suddenly stop responding to photons at exactly 700 nm. Research over the past several years has shown that far-red photons between approximately 700 and 750 nm can contribute to photosynthesis when they are supplied together with shorter-wavelength photons. This has led researchers […]
Read MorePlants outdoors rarely receive light from only one direction. Some photons arrive directly from the sun. Others are scattered by the atmosphere and clouds before reaching the plant. Still others reach leaves after reflecting from the ground, walls, greenhouse surfaces or nearby objects. These components are commonly described as: direct light diffuse light and: reflected […]
Read MoreAn outdoor PPFD curve does not always form a smooth arc from sunrise to sunset. On a clear day with an unobstructed sensor, photosynthetic photon flux density usually rises as the sun climbs higher, remains high around the middle of the day, and then declines toward sunset. But on another day, the graph may look […]
Read MoreA PAR meter shows: 650 µmol/m²/s Is that enough light for the plant? That number alone cannot answer the question. A PPFD measurement tells you the photosynthetic photon flux density at one location and one moment. But plants experience light continuously. Sunlight changes with clouds, solar angle and shade. Grow lights turn on and off. […]
Read MoreA PAR meter gives the correct reading under a 450 nm blue LED. It also gives the correct reading under a 660 nm red LED. Does that prove the meter is accurate? No. Matching a reference at two wavelengths can be a useful diagnostic check, but it does not demonstrate accurate PPFD measurement across the […]
Read MoreThe McCree Curve is one of the most frequently referenced graphs in plant-lighting discussions. It is often used to support statements such as: “Plants mainly use red and blue light.” or: “Green light is inefficient for photosynthesis.” Those statements are too simple. The original McCree research was designed to investigate how the photosynthetic response of […]
Read MoreGrow-light specifications often include three similar-looking units: µmol/s µmol/J µmol/m²/s They may look almost interchangeable, but they describe three different things. The simplest way to remember them is: µmol/s = how many photosynthetic photons the fixture produces µmol/J = how efficiently the fixture produces those photons from electricity µmol/m²/s = how many of those photons […]
Read MoreWhy are most leaves green? Why do plant-light discussions so often focus on blue and red wavelengths? And if chlorophyll absorbs green light less strongly, does that mean green photons are wasted? The answers begin with two closely related pigments: chlorophyll a and chlorophyll b These pigments are central to light harvesting in higher plants. […]
Read MoreIf two light sources deliver the same radiant power, but one puts more of that energy into red wavelengths, will it produce a higher PAR meter reading? Under carefully controlled conditions, it can. The reason comes from basic photon physics: Longer-wavelength photons carry less energy per photon. Therefore, the same amount of radiant energy can […]
Read MorePlant labels often describe light with familiar terms: Full sun Part sun Part shade Shade A PAR meter, meanwhile, may display: 350 µmol/m²/s or: 1,200 µmol/m²/s At first, these can look like two competing ways to describe the same thing. They are not. Full sun is a horticultural description of how long a location receives […]
Read MorePlant-light terminology can be confusing because PAR, PPFD and DLI are often used as though they mean the same thing. They do not. PAR defines a wavelength range. PPFD measures photosynthetic photon flux arriving at a surface at a particular moment. DLI measures how many of those photons accumulate over an entire day. Understanding that […]
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