If you feel in the dark when it comes to choosing the best grow light for plants, you are not alone. Whether you are a new grower or a seasoned veteran, the market can be more than a little difficult to navigate and there are lots of factors to consider. Factors such as quality, your budget, energy usage, the size of your grow room and the stage of plant development that the light may best suited for.

Before we start to talk about the UK’s best grow lights for plants, and LEDs for growing plants and other lighting systems, it is worth taking time to look at how your plants use light. We’ll also cover what the best grow lights for plants are, and how their output is measured. Having a good understanding of what to look out for will give you better results.

As finding the UK’s best grow light for plants is a complex topic to get a full breadth, the next few sections will cover some FAQs, which will make everything clearer.

How do plants use light?

For indoor garden’s, you need the best grow light for plants that you can afford. As you’re basically replacing the sun, you need to ensure you’re offering the full spectrum of light.

Photosynthesis

In nature, plant’s use the sun’s light for photosynthesis, how they create their food. Photosythesis is how green plants use sunlight to create sugars and carbs from nutrients, carbon dioxide and water.

Photomorphogenesis

Photomorphogenesis is the process by which plants grow and develop in response to light signals, a process that is assisted by a complex network of photoreceptors. Germination, shade avoidance, circadian rhythm, and flowering are just some responses induced in your plants by photomorphogenesis.

Best Grow Lights For Plants By Coloured Light

The colour of light provided to plants can influence their photomorphology – Blues tend to support healthy leaf and stem growth with tight internodal spacing, while red light supporting heavy fruit sets, root growth and has an elongating effect on leaves. When plants are grown exclusively under red light, the plants become leggy and sparse, with long distances between branches.

What is sunlight?

Sunlight is “full spectrum” light, meaning it contains all the different light wavelengths, making it appear white in overall appearance. It is the photon’s wavelength which determines its visible colour, a photon being a particle carrying energy proportional to the radiation frequency. The longest wavelengths are red and pass through all the colours of the rainbow, (the full spectrum) to the shortest blue wavelengths at the other end. This is the visible spectrum of light – wavelengths exist outside of this range that humans can’t see but may influence the growth of plants (infrared and UV).

The Best Full Spectrum Grow Lights For Plants

UK Full spectrum grow lights are known as “full cycle”, as they can cover your plant’s needs throughout its lifecycle.

Which wavelengths are required and when?

Primarily, plants use light in the red and blue ends of the spectrum.

What is a Grow light?

Grow lights use electricity to output an artificial light to replicate natural sunlight. Indoor grown plants use this light to grow. By controlling the intensity and timing of the lights, you can control the growing environment and can manipulate conditions to try and improve the quality, size or growth speed of the plants.

How is light measured?

Not like the picture, we can’t directly measure light like we can with distance or circumference – calculations are normally required to determine how much light your plants need.

Understanding how light is measured will help you understand the jargon used with Grow lamps, allowing you to make an informed choice and calculate the exact light exposure that plants and seedlings need. Appropriate light exposure can amongst other things, prevent pests and stop fungus from taking hold in the root zone. Relevant light measurement terms are; watts (W), nanometers (nm), lumens, PAR / PPF (umol) and PPFD (umol/m2/s). Lets have a look at the definition of each.

Watts

Watts (W) – a watt is a unit of energy measure:

• One W is equal to the flow of electrical current of one amp, at a one voltage (V).

With Grow lights the wattage is usually rated by a bulbs wattage per cm2 of its illuminated area. Or by watts per bandwidth, which is the amount of light emitted for any particular colour of light.

Watts are important to note when you are trying to figure out what the “light footprint” is for your chosen lamp. It is also useful for understanding what light footprint you need for your chosen growing space.

Light footprint means the maximum area that one lamp will cover without losing any of its effectiveness. This in turn will help you to work out how many plants you can grow under each light. The exact area will depend on what reflector you are using and the height of the reflector.

As a rule the below list shows the traditional space covered by 1x traditional HID lamp:

• 250W – 0.75m x 0.75m
• 400W – 1m x 1m
• 600W – 1.2m x 1.2m
• 750W – 1.3m x 1.3m
• 1000W – 1.5m x 1.5m

While watts are a good rule of thumb to go by for traditional grow lights, such as: HPS, MH and CFL. As Technology is improving, grow light efficiency improves, fewer watts are required to produce a similar luminosity. LED and CMH options are able to cover a larger footprint and use less electricity. When comparing the latest generation of grow light fixtures, the efficiency of the fixture will heavily influence how much light falls on the canopy.

Full Spectrum & Wavelength of light

Nanometers (nm) – a nanometer is the measure of a light’s output in terms of the amount of visible light it emits.

Visible light is the portion of the electromagnetic spectrum that is visible to the human eye. It is emitted between 400 nm (the violet end of the spectrum) and 700 nm (the red end of the spectrum).

A Grow Light’s nm range is given between 450 nm and 730 nm. Important nm measurements in grow lights are at 450 nm, 650 nm and 730 nm.

Blue wavelengths between 450 nm and 650 nm are required for photosynthesis to allow the plant to create its food.

Red wavelengths between 650 nm and 730 nm are important for flowering.

Photosynthetically Active Radiation (PAR)

Photosynthetically Active Radiation (PAR) – Not all light contributes towards photosynthesis equally:

• Chlorophyll is stimulated with blue and red wavelengths, with green contributing little towards this stimulation.

PAR is a measurement of the available light required for photosynthesis to take place. PAR is fundamental for the survival of the plant. Plants grow fastest when the PAR is highest. The most active PAR wavelength, that plants use, is in the range of 400-700 nm. Choosing lights with high levels of PAR between these ranges increases grow room efficiency as it directly facilitates plant growth and reduces harvest cycles by up to 50%.

Micromol (µmol)

You may hear measurements of PAR referred to in µmol (micromoles). A
µmol is a unit of measure used to count the number of photons emitted in the PAR range in a plant grow light system. Basically, the higher the micromoles are, the higher the PAR will be.

Photosynthetic Photon Fluxx (PPF)

Photosynthetic Photon Fluxx (PPF) – This is a measurement that determines the total amount of micromoles (umol) a fixture gives off each second.

PPF is an important measurement to understand, in order to compare the efficiencies of different grow lights. You can find out how efficient a grow light is by dividing the number of micromoles by the wattage of the unit.

This µmol per watt is a levelling factor across grow lights as it takes into account several variables. µmol is a measure of PAR output per unit of electricity, so it takes into account inputs and outputs of the fixture. Unfortunately these figures are not always available, especially on some cheaper grow lights.

Lumens for Humans

Lumens (lm) – or “lux” is a measure of the amount of “luminous flux” which is the amount of visible bright light emitted by a bulb.

The more visible light a bulb gives off then the higher the lumens.

As lumens are a measure of visible light, and plants require light beyond the visible spectrum, lumens are not really a useful indicator for a grow lights power and usefulness for growing plants under.

Recap

We’ve looked at the types of light your plants need, as well as how they use it. We’ve also covered how light is measured and why it’s useful to know when selecting grow lights. It’s now time to move on to the next question.

What Are The Best UK Grow Lights For Plants?

There are a plethora grow lights and systems out there currently. It can be overwhelming, unless you know exactly what you need.

Next we’ll look to break down the necessary information and look at each system. We’ll look to cover common “Pros and Cons”, and explain why you’d want to use certain grow lights for a stage of your plants growth.

What type of light best suits my plant’s stage of growth?

Blue light for vegetative growth

Blue light is highly suited to strong vegetative growth. This light replicates the early spring sun, sitting lower in the sky as the sun begins its ascension to its summer high.

Red light for flowering

Red grow lights are more useful for the flowering stage, as well as for strong root growth. This light replicates the autumnal sunlight as it begins to drop lower in the sky. It includes UV light and it acts as the trigger for plants to begin to set flower.

Other types of light

The Green and yellow part of the spectrum is usually reflected and is not used significantly by the plant.

Full spectrum lights are best

The best grow lights for plants provide the full spectrum of light. Full spectrum LED grow lights are the closest thing we have to being able to providing natural sunlight to our indoor gardens. Plants perform at their best when you provide the full light spectrum for different stages of their growth lifecycle. This is like simulating the sun, for optimal outdoor environment. Using white light gives them a better balance as it contains the “full spectrum” of colours, allowing the plant to perform to it’s potential.

Single Ended High Intensity Discharge (HID’s) Grow Lights

High Intensity Discharge (HID) Grow Lights are presently the most commonly used lights and are available in several variations. Metal Halides (MH) and High-pressure sodium (HPS) are interchangable using e40 mogul fittings. CMH lamps use PGZ (2 pin) fittings.

There are also HPS dual spectrum bulb and double-ended (DE) grow lights.

All types of HIDs are a type of electrical gas-discharge lamp which produces light by igniting an electric arc between tungsten electrodes inside a large bulb. The bulb is filLED with noble gas and metal salts. The gas enables the arc’s initial strike. Once the arc is started, it heats and evaporates the metallic salt’s which increases the intensity of visible light produced by the arc.

Metal halide lights (MH)

Metal halide lights (MH) burn gas that produces lighting on the blue end of the spectrum, most beneficial during the vegetative phase. Ideally you want an output of 430nm-460nm blue light and 700nm red light in order to provide high PAR that favours the blue side of the spectrum for vegetative growth.

High-pressure sodium lights (HPS)

High-pressure sodium lights (HPS) lamps burn gas that produces light on the red to orange portion of the spectrum, which is best suited for the flowering stage. They’re the most popular option, due to their consistent results and low initial costs.

HPS Dual Spectrum Lights

Light Emitting Ceramics (LEC) and Ceramic Metal Halide (CMH or CDM)

Light emitting Ceramics (LEC), Ceramic discharge metal halide (CDM) and ceramic metal halide (CMH) lights are a more recently emerging type of single-ended HID light. LEC, CDM and CMH are, in fact the same technology, LEC is actually a trademarked term for a CMH brand. They produce a spectrum of light thats much wider than a conventional fluorescent or HID bulb. They are fuel efficient, using fewer watts to produce more light and will reduce energy bills.

LEC/CMH light works just like a MH light but have a ceramic arc (like HPS bulbs) instead of a quartz one, which allows it to reach a higher temperature. This allows for a an ideal mixture of gases, which creates a fuller more useful spectrum of light.

CMH fixtures are replacing traditional options like HPS in professional gardens due to their higher efficiency and lower maintenance frequency.

Pros of CMH/LEC Lights

• Last on average twice as long as MH or HPS bulbs. They burn hotter than MH internally, but with a lower heat output, meaning less risk of plant burn and a easier to control environment.
• CMH/LEC lights have a more balanced spectrum and produce more usable light. They are more PAR efficient than HPS or MH.
• Suitable for Veg and Flowering.

Cons of CMH/LEC Lights

• Only magnetic ballasts can be used for LEC bulbs and they cannot be placed at an angle; only vertically or horizontally.
• They produce a higher level of UV light and so can pose a health risk.
• Tend to be expensive. Check out our optilux/omega CDM Kit which we believe is the cheapest CDM kit available in Europe!

HID Grow Light components

What does a lighting system consist of? HID lighting systems consist of a bulb, ballast, and a reflective light shade, designed to increase the amount of light available to the plants. They can use either a magnetic ballast, (which use coils and condensers to regulate the output), or a digital ballast (which use circuitry to regulate the lamp’s outputs). HID lighting systems come in a variety of wattages including 150w, 250w, 400w, 600w and 1000w. In terms of electrical efficiency 600w HID’s are the most effective and popular choice, producing 7% more light watt for watt than the next most effective, the 1000w HID

Pros of Single ended HID Grow Lamps

• Cheapest option to light a grow space
• Dimmable, and allow you to adjust the intensity according to your plants needs.
• Compatible with digital ballasts.
• Produce a higher percentage of usable light than fluorescent bulbs.

Cons of HID Lights

• Not very efficient
• HID bulbs produce high heat levels which can burn/damage or destroy plants if not monitored and adjusted regularly.
• They require additional equipment to operate, such as a ballast and a reflector.
• Some HID ballast will only operate MH and some will only operate HPS, meaning multiple ballasts may be required.
• The effectiveness of each bulb will decrease over time, meaning that you should change it regularly before it loses too much power.

Double-ended HID Lighting (DE HID)

Double-ended Lighting (DE) is a type of HID grow light where the lamp connects at two ends of the reflector, like a fluorescent tube. This light has its own pro’s and con’s in contrast to not only other light systems but also single ended HID’s

Pros of DE Lighting

• Double-ended HID’s lasts longer and are more efficient being as much as 90% efficient after reaching 10,000 hours.
• Operate at a higher frequency, allowing the fixture to produce more photons each second.
• Double ended lighting tubes are thinner meaning that more light will reach your plants.
• They provide up to a 10% increase on PAR output per watt in comparison to single ended HPS lights

Cons of DE Lighting

• They produce more heat than a single-ended bulb, increasing risk of plant burn.
• Double-ended lighting will mean seriously re-considering your set up logistics, as they cannot tolerate air blowing directly onto them from circulation fans. Any contact with air can affect the nitrogen inside the bulb and lower its efficiency.
• They can be considerably more expensive than other types of lighting.

T5 Fluorescent Grow Lights

T5 Fluorescent Grow Lights– Are fluorescent tube lights, most useful in the propagation stage of growth as they run cool. A T5 tube is five-eighths of an inch in diameter (hence where the 5 comes from the T is how much of an inch the bulb measure).The most common T5 grow lights are 2 or 4 ft. long and have 1, 2, 4, 6, 8 or 12 bulbs per fixture. For a few small plants you would probably only need a 2 or 4ft set up with 1-2 bulbs but if growing considerably more you would want a 4ft set up with 8-12 bulbs to cover the plants mass. 

Pros of T5 Fluorescent Lights

• Less expensive than other types of grow lights.
• Emit light that covers a larger area than most other types of grow lights.
• Much longer, useful life than other kinds of grow lights.
• Emit much less heat than other types of grow lights, so they’re suitable for tight spaces and low ceilings.

Cons of T5 Fluorescent Lights

• Not as efficient as HID options.
• Low penetration through foliage – Plants must stay short and close to the light for healthy growth.

Compact Fluorescent Lighting (CFL)

Compact Fluorescent Lighting (CFL) These lights are a high-wattage compact fluorescent that works by igniting a gas from energy produced magnetically within the environment of a seaLED tube. They have the longest life span of any grow bulb, up to 100,000 hours as their energy creates more light than heat.

Pros of CFL Lighting

• CFL lighting is up to twice as efficient as other fluorescent lighting.
• Bulbs can last for many years before losing power.
• CFL lights illuminate, brightly, instantly. There is no need to wait for them to warm up
• CFL lights burn cool with much less risk of burning or overheating your plants. Additionally using CFL’s will mean that you need less ventilation in your grow room.

Cons of CFL Lighting

• Cost of CFL lighting is quite expensive
• They are not as efficient as LEDs or HID.
• CFL lights are noisy and they interfere with Wi-Fi and cell phones.
• Lack of penetration – only fruit close to the light will properly ripen.

LED Grow Lights

LED Grow Lights – A light emitting diode (LED) is a small electroluminescent light that is extremely energy efficient and gives off very little heat. LED bulbs are perfect for growing plants under as they offer a wide light spectrum. LEDs are available in different sizes and power outputs, to provide different light footprints. A very general rule with LEDs is to have 30-40W of LED per square foot of grow room floor, compared with 50W per sq foot for traditional fixtures. An example would be, a 400W LED can cover a 10-15 square foot area—Equivalent to what a typical 600W HID unit can cover.

Full spectrum LED grow lights are very versatile. Plants flourish under both red and blue light. However, different plants require different amounts, which different colour LEDs can provide. LEDS are currently the most efficient and user controllable grow light fixtures available.

Pros of LED Lights

• LEDs are energy efficient, reducing your energy consumption by as much as 75%. They produce more light per watt than fluorescents or HIDs.
• LEDs run cooler so there is much less chance of burning your plants.
• LEDs have one of the longest lifespans, up to 100,000 hours.
• LED lights can be plugged straight in to an electrical socket, eliminating the need for a ballast
• LEDs are easy to use and effective, perfect for beginners.

Cons of LED Lights

• LEDs are an expensive outlay. However, long term, you more than make the initial cost back in savings over time.
• Some unscrupulous LED manufacturers creat LED units  that emit less light than other types of grow lights due to inferior components. To avoid this always buy a model that is at least 2.0 micromoles per watt of energy.
• Some LEDs are not powerful enough for the flowering phase. Be sure to do your research before buying so that you know you are getting the right model to meet your plant’s requirements. (we only Stock LEDS that have been proven to work with light loving fruiting annuals – Check out our product page)

Do LED Grow Lights Use Less Electricity Than Other Grow Lights?

LEDs are more energy efficient than almost all other traditional grow lights. Read our blog on LED grow lights and energy saving in your grow room to find out more about how energy efficient LEDs are. Inside, you’ll learn how much energy you can expect to use over a year or 4x 12-week growth periods.

Do LED Grow Lights Use Less Electricity?

LED grow light technology offers you vastly improved growing efficiencies. LED grow lights use less electricity, comparing PAR for PAR. This blog highlights the widening gap of running costs and shows you how to save energy at home, using them in your grow tent. When you compare grow lights power use, it’s difficult to create an argument against the best grow lights in the UK being LED grow lights.

Do LED Grow Lights Need a Ballast?

Do LED grow lights need a ballast? No. LED grow lights don’t need a ballast. LED grow lights have their power packs designed in to them. The start-up current and general power draw is much lower than comparable HID grow lights.

Sulphur Plasma Grow Lights (LEP)

Light Emitting Plasma are a solid-state light source, meaning they do not have an electrode. They use electromagnetic induction to emit light without using filaments or electrodes. To do this they use a special type of bulb called a light emitting plasma (LEP) bulb.

LEP bulbs ​contain gas that, when heated via the electromagnetic field generated by its power source, emits a light that is as close as you can get to artificially reproducing the power of sunlight. The temperature of the gas inside the bulb is 6,000K, while the surface of the Sun is 5,777K.

Pros of Sulphur Plasma Lights

• LEPs are the closest thing to actual, natural sunlight.
• They last and are effective for up to 400% longer than traditional grow lights.
• LEPs have the highest PAR rating of any grow light, maintaining up to 96% of their light output over 12 months of use.

Cons of Sulphur Plasma Lights

• LEP’s get VERY hot and must be kept a good distance away from your plants. They are not suitable for use in a confined grow room or a grow tent as they can be a fire risk.
• They are prohibitively expensive.
• LEPs fixtures can be large and heavy and awkward to hang securely and safely

What Is The Best Grow Light For Plants?

As you can see, there are many options to choose from. Lighting technology is moving fast, and new lights emerge all the time. If you read and research, you’ll soon learn there’s a lot of competition and opinion in the grow light industry. LED vs HPS, CFL vs MH. The debate will never end. Don’t let this sway your personal choice. The perfect light for you is not the perfect choice for everyone. The key is to do your research and match your specific plant’s needs with the most suitable grow light system within your budget.

Many new customers start off with budget options, such as a digital 600W ballasted with euro reflector and MH and HPS lamps once they have some experience, the light fixture is often the first thing upgraded, due to the increases in efficiency it can bring to your garden. This has shown itself time again as you seek to improve the quality and size of your harvest.