" Types of grow lights for indoor plants | Herbal House NZ

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What's the difference between grow lights?

There are three common types of grow lights you’ll come across: LED, HPS and CMH. Each lighting type comes with its own pros and cons, and today, we’re going to do a quick cross comparison to help you get started.  

HPS vs CMH grow lights 

CMH and HPS grow lights are both a type of HID - High Intensity Discharge light. 

HPS lighting typically emits a red or orange glow, which works well throughout the whole growth cycle. But its real power comes from making your plant’s flowering stage really pop.  CMH bulbs on the other hand, glow blue when lit. This is particularly good for the vegetation phase. 

If you’re trying to decide between CMH and HPS, you might want to look at their intensity – which can be measured through lumens. The more lumens, the better growth you’ll achieve. 

At Herbal House, we offer four types of HPS grow light, all ranging in power: 250w, 400w, 600w and 1000w. While each has different power, they all give out a 2100k color temperature which is a great light intensity to get started with. 

As of right now, there’s only one type of CMH bulb you can get: 315w. However, with a two-bulb reflector, you can boost this to 630w. Emitting a colour temperature of 3100k-4200k, CMH bulbs are perfect for the flowering and vegetation stages.

So while at first HPS seems to be the most powerful of the two, the CMH bulb offers more flexibility when it comes to colour spectrums needed to grow. 

Single vs. Double ended grow lights 

Single ended HPS lights have a wider bulb which is held in place with a metal frame, while double ended set ups are thinner and fastened with two small wires. 

Double ended lights can operate at much higher temperatures than their single counterparts, in turn meaning they can often be more efficient. However, with higher temperatures, you’ll need better ventilation systems and a monitor to keep track of heat. As a general guide, double ended lights are particularly good for fruit bearing trees and plants that need a lot of light. If you’re only looking to grow in a small grow tent, a single ended light will be sufficient. 

HPS grow lights vs LED 

When comparing LED with HPS, there are a fair few ways LEDs outshine HPS. HPS lights are relatively cheap to buy, but produce a lot more heat, and use a lot more energy than LEDs – pushing your electricity bills through the roof. The bulbs generally need replacing every year, too, so although they’re cheaper to buy in the first place, they’re pretty high maintenance.

LED grow lights have a larger upfront cost, but they’re generally much cheaper in the long run. LEDs are usually much more energy efficient and produce less heat – making it easier to control the temperature in your grow space. LED bulbs can last up to 10 years of use, too, so you’ll certainly get your money’s worth.  

And cost isn’t the only thing that makes LEDs so much better. HPS lighting spreads light in a way that needs to be constantly reflected around the space. Otherwise, you’ll be wasting 50% of the light emitted. Installed in our LED grow lights, we Have Samsung LM301H diodes, with an efficiency of 3.10 umol/J, well known for their efficiency and large spectrum range.

Another thing to compare between LED and HPS is PPFD rates. PPFD shows how many photosynthetically active photons are hitting your plant every second. To get the most conclusive results, it’s best to measure the PPFD from different areas of your plant to create a more realistic average. The average will allow you to see how effective your lights are for growing plants. 

For a 400w HPS light, the PPFD is around 618 μmol/m²s, with most of the light falling off around the edges. In an equivalent 4Seasons 450W Quantum board, the average PPFD is 819 μmol/m²s and is evenly distributed across the whole grow space. 

 What’s more, LEDs have dimmer switches – meaning if you do want to reach just 618 μmol/m²s you can. 

Light spectrum 

As well as light output, you need to ensure your grow light offers the right light spectrum for your plants. If you’re using a grow tent indoors, it’s key to try and replicate the plant’s natural habitat. And if that’s outside, you need to be offering your plants the full spectrum of light that they’d receive from the sun. Full spectrum LED grow lights balance out the grow light vs normal light debate: Each phase of a plant’s grow cycle requires a different colour of light to optimize growth, and full spectrum lights can easily provide this. 

Red light helps your plants to grow and bloom during the flowering stage, while blue light builds strength during the vegetative state. There’s also been recent studies into far-red light, and just how effective this light can be for optimizing plant yield.

It’s best to have everything covered in one grow light – just in case.  

And, if you’re completely overwhelmed by the whole thing, don’t hesitate to contact our team