When I first started looking into grow lights for my indoor jungle I felt totally overwhelmed.Kelvin, lumens, E27, IP, lux, this thing:"μmol/s" How could I compare my options when I didn't understand the 'light lingo' in the first place?
To save you from the big learning curve I went through, here'stheUltimate, Simplified Grow Light Guidefor Indoor Plants, explaining what all the different terms mean and answering all the common grow light FAQ's to help you compare and choose the right grow lights for your indoor plants :)
What does 'full spectrum' mean?
Full-spectrum doesn't mean sunlight. It refers to theCRIor Colour Rendering Index beingover 90, meaning the light produced is much the same as how we see colours in our natural worldlit by daylight.
What's the difference between full spectrum and pink/purple grow lights?
The 'neon pink' grow lights (sometimes called 'burple' or 'blurple')produce the red and blue spectrums only, producing a pinky-purple light. It's the red and blue spectrum that benefit plants the most to support growth, however not everyone likes that pinky glow! Plants use more of the blue and red spectrum, and less of the yellow and green. Full spectrum lights look like sunlight and appear 'white' but give plants the full spectrum, including red and blue.
How close or far away fromplants should a grow light be?
As a general rule, LED grow lights should beat least 30cmsaway from plants. You'll often see 60cm to 1 metre recommendedfor LED grow lights. Theyounger the plantthe further away it should be from a grow light. Thehigher the outputof your grow light, the further away it should be.
Some lights have more narrow, concentrated beamsso the more focused, higher intensity output means they should be further away from plants. Luckily the supplier can normallyrecommend the distance for each bulb. For example, Sunbulb recommends30cms to 1.5 metresfor their24 wattLED grow light. Youshould also take the plant's light tolerance into account also. Even if a guide says 30cms, if your plants are not tolerant of very bright or direct light, opt to start further away and adjust from there.
The type of light matters also. LED grow lights in general are higher output than fluorescent, so will typically be better hung or placed further away than fluorescents. When looking up the distance your light should be, make sure to check what type of light the guide is talking about.
What does the beam angle tell you?
Another factor that helps determine the distance a grow light should be from plants, is the beam angle. Beam angle means how wide an area the light covers (without a shade). Wide beam lights are around 45 to 120 degrees, and narrow beamvary from 5 to 45 degrees.
A narrower beamangle is more directional so can be further away from plants, witha guide of 60cms to 2 metres depending on the intensityand brightness.
A wider beam angle is a good option for using in lamps and desktop lights, as it can go closer to plants, around 30 to 120cms away. It also spreads out and covers a wider area, so if you combine a wider angle with a brighter, higher intensity light,they become good options for bigger areas like greenhouses.
How long should a grow light be on per day?
Most plants need at least 12 hours of 'Good Growth' light per day, with at least 8 hours of darkness, however will grow better with 16 to 18 hours of good light. You can look up the Good Growth level for different plant in the Plant Species Light Guidebelow.
Houseplants in general tend to be more tolerant of fewer hours of light, with 6 to 12 hours being sufficient, provided the light source is strong enough during that time, but will grow better provided with more. How long a grow light should be on depends on how many hours of 'good light' a plant gets from natural sources.A grow light can be used to supplement the good light hours, or as the only source of light if it's bright enough (again, depending on the light requirements of the plant).
Indoor plants typically get good light for only part of the day, depending on how far away from a light source they are located, time of day, time of year, and the direction the closest windows face; so in that situation a grow lightcan be used to supplement light levels to reach at least 12 hours of good lighta day.
For example, a plantthat requires bright lightand gets good natural light for 3 to 4 hours in the mornings, might have a grow light programmed to come on for 8 to 9 hours a day, starting around midday, every day.
Can you run grow lightsat night?
You can run grow lights day or night, buthaving grow lights mimic daylight hours will give you better results. However if your plants are in a dark area with little to no natural light, by all means create your own schedule for them.About12 to 16 hours lightwith a rest period ofat least 8 hours darknessis an ideal balance for most indoor plants. Take temperature into account also as combining light and warmth will get better results.
Can you keep grow lights on 24/7?
Plants need both light and darkness but how much of each they need varies by species. To grow, photosynthesis has two biochemical processes, light reaction and dark reaction. Keeping lights on 24/7 can cause stunted growth or plant tissue to die in some plants. As a general rule for indoor plants, aim for at least 12 hours of good light a day and around 8 hours of darkness.
What is Lux?
Lux tells youhow intensea grow light is, which helps you know how close or far away your grow light should be from your plants. However you still need to take into account your plant's growth stage and tolerance for bright light.
What does Kelvins tell you?
Kelvins measure the colour temperature. The higher the Kelvin, the whiter or more blue the light becomes. A lower Kelvin will be more yellow, orange or red. A cloudy sky measures around 6,000K. Direct Sunlight is 4800K.
Light bulbs below 2000K would appear similar to candlelight, are dimmer and more yellow.
2000 to 3000K is a soft white with a yellow appearance like you might use in a bedroom or lounge.
3100 to 4000K is better for task lighting like kitchens and offices.
4600 to 6000K is closer to the blue-white light of daylight, where bright illumination is needed, or when you want something lit naturally similar to the way it would be outside.
6500K and higher is a cooler, more blue-tinged light, more often used in commercial locations for very bright task lighting.
Can you use LED grow lights with power point timers?
Yes, if your grow light doesn't come with a timer, you can get yourself a power point timer, also called a plug-in timer. These start around $10 and are easy to find at hardware stores like Mitre 10 or Bunnings. Most LEDs cannot be used with dimmer switches.
Whatdoes E27 mean and what lamps do E27 bulbs fit?
The E in E27 means Edison Screw and the 27 tells you the diameter (27mms). E27 is the standard screw fitting in New Zealand.E27 gives you the biggest range of lamps and other light fittings compatible with your grow light. However keep in mind how wide the shade is matters too, because grow lights tend to be wider than household light bulbs.
If the lighthas primary or secondary optics the beam will be more directional than a grow light with no optics, meaning you can use the bulb with no shade if you prefer to maximise what reaches your plants.
The list of available lamps that fit E27 grow lights changes all the time, especially with the cheaper lighting that retailers don't have as permanent stock items. You also need to check the wattage rating is at least the same or higher than your bulb's wattage. Here are a few cheaper options with E27 fittings in stock at the time this guide was written...
Lamps:
Ceiling or wall suspension kit:
Orbit Lighting Suspension Kit Copper
Orbit Lighting Suspension Kit Gunmetal
Whatis Lumens?
Lumens measuresvisible lightfrom a light source and tells you the intensity of the light. One lumen equals one candle. One foot candle (FC) is 10.76 lumens. More lumens isn't always better. Thebrighter the lightis, thehigher the lumens. However lumens alone doesn't tell you much about grow lights as far as your plants are concerned.Lumens is more helpful for us, to measure how bright a light is tothe human eye, however PAR is what plants care about.
What is PAR and Nm (nanometers)?
Nm stands fornanometers, which measures thewavelengths of the light produced.Plants require light in the400 to 700 nmrange to photosynthesize, known asPAR(Photosynthetically Active Radiation).It's not the brightness orlumens (how bright it appears to us), but the PAR that matters to our plants.
What light levels do indoor plants require?
Each indoor plant has a different range of light it can handle from the 'minimum for maintenance' where they may stay alive, but may not do much in the way of grow, right up to commercial growth light levels that a grower might use to achieve maximum growth.
In the middle is the 'good growth' level that we aim for with indoor plants, often with the help of a grow light.This guide belowincludes some of themost popular houseplantsand thelight levels they require.
How to read the Plant Species Light Guide (below)
The first set of numbers is theMinimum for Maintenance(MM). Themiddle set of numbers achievesGood Growth(GG), and the third set of numbers is forCommercial Growth(CG).
Plants withahigher Minimum Maintenance level(the first set of numbers), are more likely to require a grow light when grown indoors, unless you can give them plenty of bright light for12+ hoursa day.If theMinimum for Maintenanceis low, this indicates thespecies is morelow-light tolerant.If theCommercial Growthlevel is low, this indicates a species thanwon't tolerate very bright lightor direct light well.
For most indoor settings,aim for at least the Good Growth level. To maintain a Commercial Growth level of light requires a more controlled setting such as a greenhouse, along with control over and close maintenance of other factors such as soil pH, airflow, temperature, humidity and fertiliser.
You'll need a goodlight meterto test the light levels, however this chart is still helpful to get an idea ofhow tolerant of low light and bright light your plant is.FCstands forFoot Candle andµmolis the symbol for a micromole, used to count the number of photons in a plant grow light system.More about both terms coming up.Note that FC varies based on the type of lightsource. The chart belowis based onsunlight requirements. Also keep in mind this guide gives you the average requirementsper species. There will be individual varieties within each species that may fall outside of these averages.
Plant Species Light Requirements Guide
KEY: See above for how to read and use this guide
African Violet
200 FC (40µmol) | 400 FC (80µmol) | 1000 to 1200 (200-240µmol)
Alocasia
200 FC (40µmol) | 400 FC (80µmol) |2000 to 5000 (400-1000µmol)
Anthurium
100 (20µmol) | 400 (80 µmol) | 1500 to 2000 (300-400µmol)
Begonia
200 FC (40µmol) | 400 FC (80µmol) |2000 to 2500 (400-500µmol)
Calathea
200 FC (40µmol) | 400 FC (80µmol) | 1000 to 1200 (200-240µmol)
Hoya
100 (20µmol) | 400 (80µmol) | 1500 to 2500 (300-500µmol)
Ficus
400 (80 µmol) | 800 (160µmol) | 2000 to 6000 (400-1200µmol)
Syngonium
100 (20 µmol) | 200 (40 µmol) | 1500 to 3000 (300-600µmol)
Monstera
100 (20µmol) | 400 (80µmol) | 1000 to 2500 (240-500µmol)
Peace Lily
50 (10µmol) | 200 (40µmol) | 1500 to 2500 (300-500µmol)
Peperomia
100 (20 µmol) | 200 (40 µmol) | 1500 to 3000 (300-600µmol)
Phalaenopsis
200 FC (40µmol) | 400 FC (80µmol) | 1000 to 1500 (200-3000µmol)
Philodendron (vining, eg: Heartleaf, Brasil)
100 (20 µmol) | 200 (40 µmol) | 1500 to 3000 (300-600µmol)
Philodendron (climbing, eg: Pink Princess)
200 FC (40µmol) | 400 FC (80µmol) | 1500 to 2500 (300-500µmol)
Pothos (Epipremnum, Scindapsus)
100 (20 µmol) | 200 (40 µmol) | 3000 to 5000 (600-1000 µmol)
Sansevieria
100 (20 µmol) | 200 (40 µmol) | 1000 to 6000 (200-1000µmol)
ZZ Plant
100 (20 µmol) | 200 (40 µmol) | 1000 to 2000 (200-400µmol)
Source: For the full list seeHouse Plant Journal >
Can you use LED house lights to grow plants?
Yes and no. Provided it's a new generation LED, at the higher brightness and intensity you might use to light a shop or for task lighting like a kitchen, then yes, some LED lights can be enough to grow low-light plants like seedlings, Peace Lily, ZZ and other low-light tolerant species. Use the Plant Species Lighting Guideabove to get an idea of low-light tolerant plants.
Even if they aren't enough to support growth, some LED house lights can still meet the minimum levels required for plants to stay alive (that's the Minimum for Maintenance set of numbers in the plant species light chart above).However in general the answer is no, for most of our tropics-loving indoor plants, you'll need a grow light tosupport growth.
What do watts tell you?
With fluorescentlights wattage was a good way to judge brightness. A 100 watt florescent is brighter than a 60 watt. But with LEDs lower wattage can produce more light than a higher wattage fluorescent. In an LED grow light the wattage really only helps you know how much electricity you'll use.
A better guide to help you judge brightness is the PPFD. Most suppliers don't tell you the PPFD for a light, however you will often be given the PAR. If you see a measurement given inμmol/m2/s orμmol-m-s that's the PPFD.
Whatis PPFD?
Plants require light in the400 to 700 nmrange to photosynthesize, known asPAR(Photosynthetically Active Radiation).PPFD and PPF both tell youthe amount of PARa light source producesthat your plants can use for photosynthesis to grow.PAR by itself tells you the quality of light only, not the quantity.
PPFDand PPF are measured in micromoles. PPFD stands for Photosynthetic Photon Flux Density and is measured in 'micromolesper square meterper second' which isμmol·m-sorμmol/m2/s.PPF stands for Photosynthetic Photon Flux and is measured in micromoles per second, which looks likeμmol-sand is sometimes shortened toμmol.
How much do grow lights cost to run?
Watts alone won't tell you how much power a grow light will use, as how energy efficient the light source is alsofactors into energy use. LED lights are much more energy efficient than other light sources. Some general costs follow to help you get a sense of power use and cost.
An oven on medium to high heat, run for one hour, will use around 2,400 watts, costing you around 60 cents depending on your power rates (all costs used are based on average rates in New Zealand).
One60 wattbulbleft on for24 hourswill cost around20 centsper day depending on your rates. Used for 8 hours a day, 7 days a week, a 60 watt bulbworks outless than 50 cents a week, oraround$24 a year.
A computerused around 3 hours a day, and unplugged when not in use, costs around $50 to $55 over the course of a year.
A 100 watt fridge or freezer costs around $100 a year to run.
What are optics?
Optics direct lighttowards your plants, increasing light intensity. Imagine optics a bit like a hose. Turning the nozzle can change both the area the water covers and also how strong the spray is. Turn one direction and you might get a veryfine spray that covers a broadarea. Turn the other way to geta single jet with much stronger water pressure that wets a smaller area. Optics work in a similar way to change the coverage (beam angle), and intensity of the light.
LEDswith no optics would have a broad 180 degree beam, light up more plants, but with weaker light intensity.Primary optics reduce the beam angle, with 90 degrees being common. In the past only primary optics were used, however some of the newer generation of lights now use secondary optics or secondary lens.
Secondary optics create a narrower beam, focusing the light to a smaller beam angle, meaning more light reaches the plants, and the light reaches further down. Light intensity increases, but how wide the coverage area is reduces.
Wide beam angles are more popular to covermore plants from furtheraway, such as for greenhouses. More narrow beams are preferred for medium distances for better depth, such as use in a grow tent or vertical cabinet.
What does the IP rating tell you?
IP stands forIngress Protectionwhich basicallytells youWhat can get in?A light's IP ratingwill give you 2 numbers, such as IP20. The first number tells you the protection against solids. The second number tells you protection again liquids.
Therating for solidsgoes from 1 to 6, with 6 being the highest level, also called'dust-tight'which offers protection against even very fine particles like dust.
Therating for liquidsgoes from 0 to 8. The highest liquid rating of 8 means the light can besubmerged under waterdeeper than a metre and for long periods of time, also called'water-proof'. A pool or pond light would need a liquid rating of 8.
Grow lights for indoor usetend to beratedfrom IP20 to IP40. That's a 2 to 4 for protection against larger solids only, and 0 protection against water.Keep in mind grow lights need airflow. Running a light in high-humidity without adequate airflow is not good for lights, or plants, or us, and can shorten the lifespan of your light or void the warranty.
Safety first: Always turn lights off at the wall BEFORE touchinga bulb. Never touch a wet bulb or light fitting without first turning the electricity off in your house.
Even a bulb rated waterproof should not betouchedif the electricity is on. To be safe, If you noticeany bulb or light fitting is wet, always turn off your electricityin your house (not just at the wall), to avoid an electric shock.
If a bulb is waterproof, the last number in the IP rating will be a 6 or above. Here's what the second number tells you (eg: the 5 in IP65).
0 has no special water protection. This rating is common for household lights in general, for the lounge, kitchen and in bathrooms where the bulb isnot directly above water (you should have a higher rating above the sink, bath and shower for example in case of water spray).
1 can resist vertical drips.
2can resist water at a 15 degree angle or less.
3 can handle water sprays up to 60 degrees.
4 means the product is water resistant to splashes from any direction (this is the rating you might have for a bulb above your bathroom sink).
5 means the bulb can handle a low-pressure water jet spray.
6 can withstand high-pressure, heavy sprays of water (thiswould be the rating you'd need for above a shower).
7 can be submerged in water up to 1 metre
8 can be submerged in water deeper than 1 metre (look for the maximum depth it can go to on the packaging)
The IP rating for water, does not relate to humidity or moist environments. When using any bulb in a high humidity environment, ensure there is adequate airflow. If you are concerned your bulb is wet, turn off the power in the house before handling. Handling dry bulbs (with dry hands), just requires turning the power off at the wall.
I do sell grow lightsbut I am not an electrician, so do recommendyou get professional advice whenchoosing lights for different uses. This advice does not replace professional advice from your electrician.
Can LED grow lights damage plants?
It's a common myth that LEDs can't damage plants. This comes from comparing fluorescentlights to LED lights. Fluorescentlights certainly do runmuch hotterthan LED, and run ahigher risk of burning plantsif they are too close, which isn't likely to happen with LEDs.
However LED grow lights still produce some heat. Not typically enough to cause damage to plants, but running hot can stilldamage the lightitself. LED grow lights are normally designed so heat exits to the back or top of the light, away from plants. This is whyairflow is importantwhen using an LED in a lampshade, not so much for your plant's sake, but for the life of the bulb (and for your wallet's sake!).
If you have your plants too close to your LED grow light, you may seeyellowing or browningon leaves. How close is 'too close' depends onyour plant's tolerance forbright light, which is why there isn't one rule for all lights or all plants. Look up thePlant Species Light Requirements Guidebelow to compare low-light and high-light tolerance.
Because LEDsrun coolerthan fluorescents, heat-burn is of little concern, but because LEDs are typically much brighter than fluorescents, you can still get 'photo-bleaching'which looks similar to heat burn, but is caused by the light being brighter than what the plant requires.
Follow the distance guide the supplier tells you, or startat least above 30cmsaway from plants, then adjust from there according to your plants individual needs. If you already know your plants are less tolerant of high light, startat60cmsand adjust from there.
Should I get 1 or 2 bulbs?
Just like the way sunlightchanges directionover the course of the day,two bulbs are better than oneif the only or main source of light to provide full coverage, rather than light from only one direction.
Where can I buy grow lights for indoor plants in New Zealand?
From me here at Love That Leaf. Shop indoor plant grow lights here >
