Providing sufficient light to your plants inside a grow space can be tricky, but using Grow lights enables your plants to thrive indoors and extend your growing season. Plant grow lights are a great tool to make your growing process more efficient, but they can also be harmful to the plant if don’t follow the proper lighting schedule. Now you might be wondering – how long should you keep grow light on or if it is recommended to leaving grow lights on 24 hours? The answer to the question is no, it is not recommended to leave your grow light 24 hours a day, because this will force plants to grow quickly. It is ideal to keep a grow light on for about 12 to 18 hours. Too much light in various growth phases can interrupt a medicinal plant’s natural process of growth and dormancy. Worse, light exposure for a whole day can damage and kill your plants.

What Happens To A Plant That Is Kept Under Constant Light?

Like humans and animals, plants need a break from direct light, too. Imagine they need to sleep as well. When medicinal plants absorbs a lot of light, they will constantly engage in photosynthesis. On the bright side, this will result in the maximum growth of foliage. Yet, there are consequences as well. If your medicinal plants are constantly exposed to light, especially during the vegetative stage, they may experience stress. Once they get exposed to diseases, they also become susceptible to pests, and consequently, diseases and death.

Factors To Consider: How Long Should I Leave Grow Lights On?

Here are important factors to remember when planning how long to leave grow lights on:

  • Type of Plant
  • Growth Phase
  • Type of Light
  • Temperatureand Humidity
  • Size of Grow Space

Type Of Plants

It is better if you are familiar with the kind of plant. There are three types: low-light, medium-light, and high-light plants. A seed box must show the plant type.

Low-light plants should get about 4 hours of artificial light. On the other hand, medium-light plants require about six hours of light exposure. Meanwhile, high-light plants need about 14 to 16 hours of light.

Growth Phases

Light and dark cycles depend on the growing stage. Each phase requires a specific duration of light exposure to successfully complete the growing state.

  • Cloning/Seedling State: Should Seedlings Get 24 Hours Of Light?

No, that is a terrible idea. This is one of the most critical phases of plant growth, so growing conditions should be ideal. Seeds would find it hard to germinate when exposed to constant light. Thus, the advisable light-dark cycle for seedlings is 16 hours on and then 8 hours off.

While it is true that seedlings need lots of light to grow, they also need darkness to survive. Since seeds are still ‘baby’ plants, they require a dark time to undergo respiration.

  • Vegetative State

The vegetative phase needs more light to sustain growth. But this also means the medicinal plants must rest for at least 6 hours.

Hence, the ideal light-dark cycle must be 18 hours on and 6 hours off. The plants will not grow taller as you expect it to be from 24-hour exposure. Yet, this cycle provides you a healthier growth.

As long as you follow suggested light-dark cycles, the plant will be able to form lots of leaves and a solid stem.

  • Flowering State

For this phase, buds will begin to form nice and stinky. The lights should help produce potent and big buds that are suitable for smoking or making edibles.

A bigger area coverage doesn’t necessarily need bigger light wattage.The flowering stage won’t focus on growing taller, but it will make sure your plants get wider.

At this state, you can’t leave the lights on for 24 hours. Otherwise, the medicinal  plants will stay in the vegetative stage. Thus, it’s best to follow the light-dark cycle of 12 hours on and 12 hours off. Plants have mechanisms that let them know if there’s less light. The transition from lightness to darkness enables the plants to grow full flowers.

Type Of Grow Light

Since you are using artificial lights, medicinal plants will need longer hours of light exposure.

Although the vegetative phase benefits from 24-hour light exposure, the rest of the stages needs light and dark cycle. The type of grow light also plays a key role in this matter.

This type of light produces certain, yet complete light spectrum wavelengths. It supports photosynthesis, as well as all growth phases. The best part is that although LED lights generate great power, they only consume low energy. On the downside, LEDs can be damaging to the human eye. They are also pricier than regular lights.

  • Compact Fluorescent Lights

You can place CFLs about six to seven inches away from your plants. The downside is that unlike LED lights, CFLs are not fitted with cooling systems.

HIDs are the go-to lights for growers who are on a tight budget. Unfortunately, they are less powerful than LED lights. In addition, they are more prone to heat. This is why I recommend using a mirror or foil underneath the medicinal plants. In this way, the light can reflect towards the foliage.

  • Metal Halide Lights

MH lights produce a large amount of light per watt. On the flip side, the bulbs emit a lot of heat, which may cook seedlings.

Temperature And Humidity

Lights impact temperature, and subsequently, humidity.It is ideal to keep the temperature inside a grow space between 72 to 82 degrees Fahrenheit. Meanwhile, relative humidity must be around 30% to 40%.

Size Of Grow Space

A bigger area coverage doesn’t necessarily need bigger light wattage. Regardless of the type of light, here’s a general guideline of how many watts you need for a grow area.

1 x 1: 32 watts
2 x 1: 64 watts
2 x 2: 128 watts
3 x 3: 288 watts
3 x 4: 384 watts
4 x 4: 512 watts
4 x 5: 640 watts
5 x 5: 800 watts
5 x 6: 960 watts
6 x 6: 1152 watts

Here are three best LED grow lights. Let's have a look together!

ECO Farm 600W Assemble Samsung 301H LED Grow Light Adjustable Beam With Meanwell HLG 600H 54B Driver

  • ECO Farm 600W LED light is a high-performance top-lighting solution for commercial horticulture cultivation. Designed for growers to push the envelope with high-PPFD cultivation practices.
  • The updated structure with an adjustable beam distribution rack and offers the possibility of adjusting the 600W LED grow light concentration along the rods, making application in different areas more flexible.
  • It also has an anti-sulfur coating unique to horticulture, which further increases the chip's durability.
  • Optimized full-spectrum, suitable for all growing stages from seed to harvest
  • In addition, Meanwell HLG 600H 54B driver with high voltage capacitors, ensuring LED chips lifetime of up to 50,000 hours.
  • The latest high-efficiency Samsung 301H 3500K chips + Epistar 660nm chips, with much better PAR efficiency results.
  • Certification: CE, EMC, FCC, LVD,
  • Warranty: 3-year

ECO Farm ECOZ Pro 700W/1000W UV+IR LED Samsung 301H Grow Light Strips

ECO Farm ECOZ Pro 700W/1000W series was the latest trend and most popular for its good design and ease of use.

Full spectrum: the light include IR and UV which is similar to the sunshine, ideal for all kinds of indoor plants veg and flower at all growth stages.

Three channels: veg, bloom, UV.
It is a perfect top-lighting solution for commercial horticulture cultivation, or a full-cycle top-lighting solution for home hobbyists cultivating.

ECO Farm MB2 660W/720W Foldable LED Grow Light With Samsung 301B Chips Full Spectrum Light Strips

  • ECO Farm MB2 660W/ 720W light using the highest output Samsung 301B LED chips and Osram 660nm chips, efficacy is up to 2.7umol/J. High PPF is up to 1782μmol/s. Ultra-high PPFD than Fluence/Gavita.
  • Advanced Sonsen LED driver can provide higher performance
  • Full-spectrum grow light, Samsung 301B white light, and enhanced Osram red 660nm, good for full-cycle growth, high yield
  • 180° Folding design, just hang it up and plug and play, very convenient and flexible to adapt to different growing areas
  • Standard 0-10V knob dimming, support the daisy chain RJ port
  • UL, DLC, CE, ROHS certified
  • Big footprint: suitable for large-scale use in greenhouse, commercial growing space etc.

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