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 MoreWhat Research Actually Supports About Light, CO₂, Water, Bitterness and Regrowth Turnip greens are the edible leaves of Brassica rapa, but there is no scientifically established PAR, CO₂ and VPD recipe that guarantees tender leaves, mild flavor or stable regrowth. This distinction matters because turnip quality depends on much more than three environmental numbers. Published […]
Read MoreWhat Research Actually Supports About Light, CO₂, Water, Leaf Quality and Hidden Stress Beet greens are the edible leaves and petioles of Beta vulgaris, usually harvested from beet cultivars that may also be grown for their roots. They can look remarkably robust. Broad leaves, colorful veins and thick petioles can make beet greens appear tolerant […]
Read MoreCollard greens (Brassica oleracea var. viridis) are productive leafy Brassicas capable of growing under substantial light, but there is no scientifically established PAR, CO₂ and VPD recipe that applies to every greenhouse and every growth stage. Published collard research gives us useful evidence about: But the evidence does not support simple rules such as: high […]
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 greenhouse crop with a long production cycle, large leaf area and substantial demand for light and water once fruit production begins. That can make greenhouse eggplant appear straightforward: provide strong light, warm temperatures and enough irrigation, and the crop should perform well. Research shows that the reality is more […]
Read MoreChili peppers are often described as heat-loving, high-light crops. That description is broadly useful, but it can lead to a dangerous greenhouse assumption: more light + more heat + more CO₂ = more chili yield. Research shows a much more complicated picture. Light can increase photosynthesis and fruit production. Elevated CO₂ can stimulate growth. Mild […]
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 MoreIceberg lettuce, also called crisphead lettuce, differs from loose-leaf lettuce in one important way: the crop is not simply producing leaves. It must also form a compact marketable head. That makes environmental management more complicated. Conditions that rapidly increase leaf biomass do not necessarily produce the best head formation, and rapid growth can increase the […]
Read MoreEndive (Cichorium endivia) is a cool-season leafy vegetable that includes two closely related forms: curly endive (C. endivia var. crispum) and broad-leaved escarole (C. endivia var. latifolium). Like lettuce, endive responds strongly to light, temperature and water availability. But treating it as simply “another lettuce” can be misleading. Research shows that endive growth, leaf morphology […]
Read MoreLovage (Levisticum officinale) is a perennial culinary herb in the Apiaceae family, related to celery, parsley and dill. It can develop into a very large plant, with strongly aromatic leaves and stems, and this robust appearance can make lovage seem like a crop that simply benefits from more light and stronger environmental inputs. Research does […]
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 MoreFennel (Foeniculum vulgare) is an aromatic crop, but “fennel” can describe plants grown for quite different purposes. Common or leaf fennel is primarily harvested for its feathery foliage, stems and aroma. Florence fennel (Foeniculum vulgare var. azoricum) is grown for its enlarged, bulb-like stem bases. That distinction matters when greenhouse conditions are discussed. A lighting […]
Read MoreLeeks are slow-growing compared with many greenhouse vegetables. But their slow growth does not mean they require a special sequence of: low PPFD → medium PPFD → high PPFD → lower preharvest PPFD. Direct leek research points to a different set of priorities. Light matters. But so do: water supply temperature plant spacing nitrogen cultivar […]
Read MoreBasil microgreens have a short production cycle, but their lighting requirements are more complex than simply choosing the highest possible PPFD. Light can influence: The result also depends on: That is why there is no single scientifically established “best PPFD” for every basil microgreen crop. Recent controlled-environment research has successfully grown basil microgreens across PPFD […]
Read MoreHow PAR, CO₂ and VPD Affect Growth, Stem Length and Crop Quality Radish microgreens grow quickly, but their short crop cycle does not make environmental measurement unimportant. Light intensity, daily light, temperature, humidity and vapor pressure deficit (VPD) can all influence growth. CO₂ is also part of the photosynthetic environment, although current research does not […]
Read MoreWhat Research Actually Supports About Light, CO₂, Temperature, Tipburn, Aroma and Shelf Life Chervil (Anthriscus cerefolium) is a delicate leafy herb valued for its fine foliage and mild anise-like flavor. It is often treated as a lighter version of parsley. Research shows that this comparison is too simple. Chervil has direct crop-specific evidence showing important […]
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 MoreSweet pepper (Capsicum annuum) is a long-cycle greenhouse crop. A healthy plant can have: large leaves thick stems many flowers and still produce: poor fruit set strong week-to-week yield fluctuations or: too many aborted young fruits. That is because sweet pepper yield is not controlled by one environmental number. Fruit production depends on the balance […]
Read MoreWhat Research Actually Supports About PAR, DLI, CO₂, Water, Nutrition and Harvest Quality Wheatgrass is the young vegetative shoot of wheat, most commonly Triticum aestivum L., harvested well before the crop reaches the reproductive stages associated with grain production. Its short production cycle can make it appear simple. Seeds germinate rapidly, leaf blades emerge quickly, […]
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 MoreMustard microgreens grow quickly, develop strong color and have a distinctive pungent flavor. But there is no scientifically established single PPFD, DLI, CO₂ concentration or VPD that can be described as the universal “best” environment for every mustard microgreen crop. Controlled-environment research shows something more useful: Mustard microgreens can grow successfully across a range of […]
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, Water, Stem Strength and Shelf Life Sunflower shoots and sunflower microgreens are young seedlings of Helianthus annuus, normally harvested while the cotyledons are expanded and the first true leaves are only beginning to develop. They look robust. Sunflower shoots have: That appearance can make them seem almost impossible […]
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 MoreMizuna is a fast-growing Japanese leafy Brassica valued for its: mild peppery flavor, deeply serrated leaves, rapid harvest cycle, and ability to regrow after cutting. It is often treated like a generic leafy green. But direct controlled-environment research shows that mizuna responds strongly to: PPFD Daily Light Integral photoperiod spectrum and: temperature. Most importantly, there […]
Read MoreRadish (Raphanus sativus) is one of the fastest vegetable crops to grow. That short crop cycle can make greenhouse radish look simple. But producing: large uniform crisp and: non-hollow storage roots is more complicated than producing a large canopy. Radish responds strongly to: light quantity light spectrum CO₂ root-zone temperature water availability plant spacing and: […]
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, Regrowth, Water, Texture and Shelf Life Green onions, scallions, Welsh onions and Japanese bunching onions are names commonly used for non-bulbing or weakly bulbing Allium fistulosum crops. They are fast-growing leafy Alliums valued for: Their rapid growth can make them appear almost impossible to stress. But there is […]
Read MoreWhat Research Actually Supports About Light, CO₂, Glucosinolates, Water, Flavor and Shelf Life Mustard greens, commonly Brassica juncea, are fast-growing leafy Brassicas valued for their distinctive peppery flavor. They can be harvested as: But these production stages are not physiologically identical. There is no scientifically established stage-by-stage combination of: PAR CO₂ and: VPD that guarantees: […]
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 MoreWhat Research Actually Supports About Light, CO₂, Regrowth, Water, Temperature and Leaf Quality Chives (Allium schoenoprasum L.) are perennial culinary herbs grown primarily for their hollow green leaves. They tolerate repeated cutting and can remain productive for a long period, which makes them look like a simple greenhouse crop. But chives have a more complicated […]
Read MoreSwiss chard is a productive leafy crop, but there is no scientifically established PAR, CO₂ and VPD recipe that applies to every cultivar and every stage of greenhouse production. PAR supplies the photons used for photosynthesis. CO₂ supplies carbon. Temperature and humidity determine the plant-air moisture environment, commonly described using vapor pressure deficit (VPD). These […]
Read MoreArugula (Eruca sativa), also called salad rocket, is a fast-growing leafy crop that responds strongly to light. But there is no scientifically established PAR, CO₂ and VPD recipe that applies to every greenhouse and every growth stage. For arugula, published research gives us particularly useful evidence about: The evidence for one precise arugula-specific VPD optimum […]
Read MoreSage (Salvia officinalis L.) is a Mediterranean aromatic herb that generally performs well under bright conditions, but there is no scientifically established PAR, CO₂ and VPD recipe that applies to every greenhouse and every growth stage. This is especially important for sage because different growers may be optimizing for very different outcomes: The environmental condition […]
Read MoreOregano is a Mediterranean aromatic herb, but there is no scientifically established PAR, CO₂ and VPD recipe that applies to every oregano plant, greenhouse and stage of production. This is especially important because “oregano” can refer to genetically and chemically different plants. Even within Origanum vulgare, different: can produce substantially different essential-oil profiles. One oregano […]
Read MoreThyme is a Mediterranean perennial herb adapted to bright environments, but there is no scientifically established PAR, CO₂ and VPD recipe that applies to every greenhouse, cultivar and stage of production. This is particularly important for thyme because growers may be optimizing for different outcomes: These outcomes do not always peak under the same environmental […]
Read MoreRosemary is a Mediterranean perennial herb that generally performs well under bright conditions, but there is no scientifically established PAR, CO₂ and VPD recipe that applies to every greenhouse and every stage of rosemary growth. This is especially important for rosemary because production goals can differ. A grower may want: Those objectives do not always […]
Read MoreDill is a fast-growing culinary herb, but there is no scientifically established PAR, CO₂ and VPD recipe that applies to every greenhouse, cultivar and stage of production. Light provides the photons used for photosynthesis. CO₂ supplies carbon. Temperature and humidity shape the plant-air moisture environment commonly described using vapor pressure deficit (VPD). For dill, published […]
Read MoreParsley is a leafy culinary herb, but there is no scientifically established PAR, CO₂ and VPD recipe that applies to every cultivar and every stage of greenhouse production. Light supplies the photons used for photosynthesis. CO₂ supplies carbon. Temperature and humidity shape the plant-air moisture environment, commonly described using vapor pressure deficit (VPD). For parsley, […]
Read MoreCilantro (Coriandrum sativum), also called coriander, is often described as a cool-season herb that prefers good light but bolts quickly when growing conditions become unfavorable. That description is useful. But cilantro lighting is more complicated than: “Give it moderate light and keep PPFD below 700 µmol/m²/s.” Controlled-environment research shows that cilantro responds strongly to: PPFD […]
Read MorePeppermint (Mentha × piperita L.) is a fast-growing aromatic herb, but there is no scientifically established PAR, CO₂ and VPD recipe that applies to every greenhouse and every stage of production. This is particularly important for peppermint because plant appearance is only part of the production goal. Growers may be optimizing for: These outcomes do […]
Read MoreSweet basil (Ocimum basilicum) responds strongly to its light environment, temperature, humidity and carbon dioxide supply. However, there is an important limitation when discussing “ideal” PAR, CO₂ or VPD values: There is no single scientifically established PAR, CO₂ and VPD recipe that applies to every basil cultivar, greenhouse and growth stage. Published basil studies use […]
Read MoreGreenhouse spinach is a fast-growing leafy crop, but its performance cannot be explained by light alone. PAR provides the photons used for photosynthesis. CO₂ provides the carbon used to build sugars and biomass. Temperature and humidity determine the plant-air moisture environment, commonly described using vapor pressure deficit (VPD). These variables interact. A spinach canopy may […]
Read MoreKale is a productive cool-season leafy crop, but there is no scientifically established set of PAR, CO₂ and VPD values that applies to every cultivar and every stage of greenhouse production. Light supplies the photons used in photosynthesis. CO₂ supplies carbon. Temperature and humidity shape the plant-air moisture environment, commonly described using vapor pressure deficit […]
Read MoreLettuce is often described as an easy controlled-environment crop because its production cycle is relatively short. That does not mean its environmental requirements can be reduced to one light intensity, one CO₂ concentration and one VPD value. A lettuce seedling, a rapidly expanding plant and a nearly market-ready head do not have identical leaf area, […]
Read MoreGreenhouse strawberries are often managed using a list of environmental targets: a certain light level, a CO₂ concentration, a temperature range and a VPD setpoint. The problem is that strawberries do not respond to these variables independently. CO₂ enrichment can increase photosynthesis and yield, but its benefit depends on temperature and available light. Temperature influences […]
Read MoreCucumbers are fast-growing, high-light crops once they develop a large canopy and begin producing fruit. But there is no single PPFD number that applies to every cucumber plant from germination through harvest. A young plug seedling and a mature greenhouse cucumber differ dramatically in: For that reason, cucumber lighting is better evaluated using: PPFD — […]
Read MoreGreenhouse tomato production is not controlled by light alone. Tomatoes use photosynthetically active radiation (PAR) as the energy source for photosynthesis, CO₂ as the carbon source for building carbohydrates, and the surrounding temperature and humidity determine vapor pressure deficit (VPD), which influences transpiration and stomatal behavior. These factors interact. A tomato canopy may receive strong […]
Read MorePlant growth is often discussed one variable at a time. How much light does the crop need? What CO₂ concentration is best? What VPD should the greenhouse maintain? Those are useful questions, but plants do not experience light, carbon dioxide and atmospheric moisture independently. They experience them at the same time. Light provides energy for […]
Read MoreWhen I first started measuring light for my plant collection, I naturally looked for the simplest tools available. My smartphone was always with me, and I downloaded a few light meter apps that claimed to estimate PAR (Photosynthetically Active Radiation). Many of these apps worked fine for a few measurements, but soon I encountered “premium” […]
Read MoreWhen I first started using a smartphone to estimate light for my plants, I quickly discovered that the camera’s standard settings were not enough. I would point my phone toward a grow light or near a window, and the default camera view would show one set of brightness values. At the same time, a “night” […]
Read MoreWhen I first started experimenting with grow lights for my indoor plants and seedlings, I naturally reached for the tools I already had at hand — primarily my smartphone’s light meter apps and the camera. I assumed that if the phone said a spot was bright, the plants would be getting plenty of usable light. […]
Read MoreFor years I used my smartphone camera and light meter apps to gauge how much light my plants were getting. It seemed straightforward: open the app, point the camera at the light source or plant canopy, and get a number. If the number was high, I assumed the plant had enough light. If it was […]
Read MoreCan a smartphone measure plant light? Yes — but the answer depends on what is being measured and how the phone is used. Modern smartphones contain optical sensors and cameras capable of measuring or estimating light. With suitable software, calibration and measurement methods, a smartphone can be useful for: But a phone displaying a PPFD […]
Read MoreFiddle leaf fig (Ficus lyrata) is usually described as a plant for: bright indirect light. That is good practical advice for many indoor plants. But it is not the whole story. Outdoors in suitable tropical and subtropical climates, Ficus lyrata can grow in: full sun as well as: partial shade. At the same time, an […]
Read MoreSnake plant has one of the strongest low-light reputations of any houseplant. That reputation is justified—but often misunderstood. Dracaena trifasciata, formerly known as Sansevieria trifasciata, can tolerate light conditions that would cause many other houseplants to decline. That does not mean: darkness is ideal or: more light makes no difference. Light influences: growth rate leaf […]
Read MorePothos (Epipremnum aureum) has a reputation for being one of the easiest low-light houseplants. That reputation is partly deserved. Pothos can survive—and even continue growing—under remarkably low indoor photon levels. But: low-light tolerance does not mean light has little effect on the plant. Research shows that photon supply can strongly influence: growth rate total leaf […]
Read More“Bright indirect light” is probably the most common lighting recommendation for Monstera deliciosa. It is also difficult to measure. A location that looks bright to the human eye may provide very little photosynthetic light, while another location near a window may briefly receive extremely high light. PPFD and Daily Light Integral (DLI) provide a more […]
Read MoreKalanchoe is often described as a succulent that likes: bright light and: short days for flowering. Both statements are broadly correct. But they describe two different biological functions. Light quantity affects: photosynthesis, biomass, compactness and flower number. Photoperiod—especially the length of the uninterrupted night—can determine whether some Kalanchoe species initiate flowers at all. This distinction […]
Read MoreAloes are usually described as: sun-loving succulents. That is broadly correct. But the genus Aloe contains hundreds of species with different: growth forms, native habitats, temperature tolerances, and responses to solar exposure. Even within one species such as Aloe vera, research shows that “more light is better” is too simple. Full sunlight can strongly increase: […]
Read MoreSempervivum—commonly called hens and chicks or houseleek—is generally considered a high-light succulent. Strong light can help maintain: compact rosettes short, dense growth and: characteristic foliage color. But that does not mean every Sempervivum requires: 500–800 µmol/m²/s or: 25–32 mol/m²/day. Current research does not establish one universal PPFD or DLI target for the genus. And there […]
Read MoreJade plant (Crassula ovata) is often described as a “bright-light” succulent. That description is useful, but it does not tell you exactly how much light reaches the plant. A south-facing window, an east-facing window and a grow light can all look bright to the human eye while delivering very different photon quantities. This is where […]
Read MoreEcheverias are usually described as: bright-light succulents. That is broadly useful advice. But it does not answer the questions growers increasingly ask: What PPFD does Echeveria need? What DLI keeps a rosette compact? Does stronger light improve red coloration? Does Echeveria need very high light to flower? Research now gives us much better answers than […]
Read MoreGeraniums generally perform best with substantial light. But there is no scientifically supported rule saying that they require: 15–20 mol/m²/day as seedlings then: 20–28 mol/m²/day during vegetative growth and finally: 28–35 mol/m²/day for flowering. Research on geraniums gives us a much more useful picture. Light quantity affects: rooting biomass plant compactness and: flower development. But […]
Read MorePetunias generally perform best with substantial light, but there is no single PPFD or DLI number that applies to every cultivar and every stage of production. Light requirements change with: Research shows that increasing Daily Light Integral can improve petunia branching, biomass and flowering. But it also shows something equally important: Petunias do not need […]
Read MoreThere is no single light requirement for every holly. The genus Ilex includes hundreds of species adapted to different: climates, forest positions, soil conditions, and light environments. For example: American holly (Ilex opaca) is highly shade tolerant and naturally occurs as an understory tree. Yaupon holly (Ilex vomitoria) can tolerate anything from full sun to […]
Read MoreBoxwood is often described as a plant for: full sun part shade or: dappled shade. All of those descriptions can be correct. That is because boxwoods are relatively adaptable evergreen shrubs, and different: species, cultivars, climates, seasons, and planting locations can produce very different results. What is not supported by current research is a rule […]
Read MoreOxalis triangularis, commonly called Purple Shamrock, is valued for its dark purple triangular leaves, delicate flowers and distinctive daily leaf movement. Its light requirement is often described with phrases such as: bright indirect light partial shade or: some direct sun. Those descriptions are useful. But growers increasingly want a more quantitative answer: What PPFD does […]
Read MoreThere is no single PPFD or DLI target for “orchids.” The orchid family includes plants adapted to very different environments. A Phalaenopsis growing beneath filtered tropical canopy light does not have the same light requirement as a higher-light Cattleya. A Paphiopedilum can perform under comparatively modest light, while some Dendrobium groups tolerate substantially brighter conditions. […]
Read MoreAfrican violets are flowering houseplants that can grow and bloom under much lower photon levels than many vegetables, herbs or sun-loving ornamentals. That makes them a useful example of why: more PPFD is not automatically better. An African violet needs enough photons to support: leaf development flower initiation and: continued flowering. But excessive direct sunlight […]
Read MoreBeets are unusual because we can harvest both: the leaves and: the swollen storage organ below the canopy. That makes light interpretation especially interesting. A beet growing under reduced light may still maintain a reasonable-looking leaf canopy while producing a much smaller storage organ. Controlled-environment research has directly demonstrated this response. So the important question […]
Read MoreCarrots develop their edible storage roots underground. But those roots depend on the leaves above ground. The canopy captures light, performs photosynthesis and supplies carbohydrates that support: leaf growth storage-root thickening and: overall biomass accumulation. That means light matters for carrots. But the scientific evidence does not support a universal table saying: seedlings need one […]
Read MoreMicrogreens are not a single crop. Radish, broccoli, arugula, mustard, basil, pea, sunflower, beet and amaranth can all be grown as microgreens, but they differ in growth rate, stem structure, pigmentation, harvest timing and response to light. That makes it difficult to justify one universal PPFD or DLI target for “microgreens.” Published production guidance instead […]
Read MoreFlowering tobacco is usually described as a sun-loving ornamental. That is broadly correct. But it does not mean that Nicotiana requires one exact PPFD or DLI at each growth stage. Common ornamental species such as: Nicotiana alata Nicotiana sylvestris and: Nicotiana langsdorffii can grow in environments ranging from: full sun to: partial shade. Their flowering […]
Read MoreStrawberries need substantial light to support leaf growth, flowering and fruit production. But there is no single PPFD number that every strawberry plant should receive at every stage. Light requirements depend on: For this reason, strawberry light is better evaluated using two measurements together: PPFD — instantaneous photon flux at the canopy and: DLI — […]
Read MoreParsley can grow successfully under a fairly broad range of light conditions. Garden recommendations commonly place it in: full sun to partial shade. But quantitative production research shows that light still matters. Increasing Daily Light Integral can increase: fresh biomass, dry biomass and harvestable yield under some production systems. At the same time, parsley does […]
Read MoreMint is often described as an easy herb that grows in both sun and partial shade. That description is broadly useful. But it does not mean that light has little effect on mint. Research shows that changing photon supply can affect: biomass, branching, leaf structure, essential-oil production and terpene yield. At the same time, there […]
Read MoreBasil is often described as a high-light herb, but there is no single PPFD or DLI value that is ideal for every basil cultivar, production system or growth stage. Sweet basil grown outdoors in full sun experiences a very different light environment from basil grown under LEDs in an indoor farm. Seedlings, harvest-stage culinary basil […]
Read MoreKale is a leafy Brassica crop that can perform well across a relatively wide range of controlled-environment conditions. That does not mean there is one universal PPFD, CO₂ concentration or VPD that should be used from seedling to harvest. As kale develops, leaf area increases, canopy structure changes, total photon interception rises and crop water […]
Read MoreSpinach is a cool-season leafy crop that responds strongly to its light environment, but there is no single PPFD or DLI value that is ideal for every spinach cultivar, production system or growth stage. Spinach grown outdoors in cool spring weather experiences very different conditions from hydroponic spinach grown under LEDs. Temperature, photoperiod, cultivar, spectrum […]
Read MoreGreenhouse lettuce grows quickly, but that does not mean it should simply receive as much light, CO₂ and airflow as possible. Lettuce is a leafy crop with a relatively short production cycle. Its growth responds strongly to daily light, carbon dioxide and atmospheric moisture conditions, but these variables also interact with temperature, cultivar, irrigation, nutrient […]
Read MorePeppers are high-light crops, but there is no single PPFD or DLI number that is ideal for every pepper plant at every stage. Cultivar, plant age, photoperiod, temperature, greenhouse transmission, canopy density and production goals all affect how much light a pepper crop can use. For that reason, PAR and DLI are most useful as […]
Read MoreCucumbers are fast-growing, light-demanding plants, but there is no single PPFD or DLI value that applies to every stage of growth. A young cucumber seedling has very different light requirements from a mature greenhouse vine carrying multiple fruits. Cultivar, photoperiod, temperature, greenhouse transmission, canopy density and production system all influence how much light a cucumber […]
Read MoreTomatoes are high-light crops, especially once they develop a large canopy and begin producing fruit. But there is no single PPFD number that is correct for every tomato plant at every stage. A seedling in a propagation tray, a young transplant, and a mature fruiting greenhouse tomato have very different: For that reason, tomato lighting […]
Read MorePlant growth is often discussed one measurement at a time. A grower checks PPFD and asks whether the light is strong enough. Another looks at DLI and asks whether the crop received enough light during the day. A greenhouse operator checks CO₂ concentration and asks whether more carbon dioxide would improve photosynthesis. All three measurements […]
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 MoreNot every plant needs the same amount of light. A PPFD or DLI value that strongly limits one species may still support another. This is why some plants can maintain healthy foliage and continued growth in locations that would be unsuitable for: tomatoes, peppers, high-light succulents, or other strongly sun-adapted plants. But the explanation is […]
Read MoreA plant receives its recommended Daily Light Integral, but the PPFD never becomes particularly high. Is that a problem? Not necessarily. A sufficient DLI does not require a high peak PPFD. DLI measures the total quantity of photosynthetic photons received during a day. The same DLI can be delivered with relatively high PPFD for a […]
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 light curve does not always form a smooth arc from sunrise to sunset. On a clear, unobstructed day, PPFD may change relatively smoothly as the sun rises, reaches a high solar elevation and later descends. But under broken clouds, moving foliage or changing local shade, the graph can look very different. Around midday, […]
Read MoreMeasuring plant light outdoors is different from taking a quick reading under an indoor grow light. An outdoor sensor may experience: rain, dew, wind, direct sunlight, rapid temperature changes, moving shadows, dust, and plant growth around the measurement position. These factors do not all change sunlight itself. But they can change: the sensor, its orientation, […]
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. […]
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