How long to keep grow lights on indoor plants?

Growing plants indoors offers many benefits. The most significant advantages are that it helps prevent garden pests and to control the weather. Furthermore, unless you are lucky enough to have a greenhouse or solarium attached to your home, offering sufficient light to your plant may be a challenge.

Although south-facing doors and windows may offer enough light for a pot of seedlings, growing vegetables or any other sun-loving plants to maturity will require artificial lightings. Plants need more time in the light when grown under grow lights but determining how much depends on the individual plant requirements, the light intensity, and the kind of lighting you provide.

How much light do indoor plants need

How much light do indoor plants need?

Growth quality in most crops is dependent on the hours of darkness they get, as well as the light period.

However, it is unnecessary to leave your grow lights on 24/7. Plants require a light-dark cycle to thrive properly. During the day, light helps plants produce energy for photosynthesis, while during the night, they break down energy for growth and flowering process known as respiration.

A basic guideline to remember is that if your plant is a vegetable or it is at its flowering stage, it requires 12-16 hours of light in the day and 8 hours during the night.

Here are some examples of how much light is needed for specific crops-

Plants that require 6 to 8 hours of light:

  • Cherry Tomatoes
  • Basil
  • Strawberries
  • Thyme
  • Rosemary

Plants that require 8 to 12 hours of light:

  • Fern
  • Begonia
  • African Violet

Plants that require 14 to 18 hours of light:

  • Cucumbers
  • Aloe Vera
  • Figs
  • Large Tomatoes

The citrus trees tend to grow huge, even in small sizes, so they will require a bigger space to thrive and larger lights hanging 6 to 12 inches from the plants. Furthermore, you will need to keep your light about 6 to 8 inches away from the plants to avoid burning the crop. If you have various plants and some need to be closer, you can prop them up to have adequate room for growth.

How Much Light Do My Plants Need?

5 Things to Consider Before Measuring The Lighting Duration

Light Spectrum

 The light quality impacts how much light a plant requires. Plants require light on the red and blue spectrums produced using a full-spectrum fluorescent bulb or lamps labeled grow light. Incandescent lamps only give light on the red spectrum. Besides, they have a shorter life and emit substantial heat, which can damage heat-sensitive plants.

Light Intensity

The light intensity can be measured in candelas per square meter. Most indoor plants require between 50-1,000-foot candelas from either sunlight or artificial light. If the plant requires little light or gets some light from a window, regular lighting from ambient light sources in the room may be enough. Plants requiring medium light need at least 250-foot candelas to grow better with a small grow light setup when they are not near a sunny window.

Seedlings such as vegetables and tomatoes that grow in full sun require 1,000-foot candelas or more intensity light. So, intensive grow light setups that have at least four light tubes may be suitable for healthy growth. Light intensity also varies depending on how near the plant is to the light. For instance, plants placed 6 inches under a two-light set up receive 500-foot candelas, while those sitting 3 feet from the light fixture only receive 60. Read our latest article about how many lumens does a plant need.

Power Consumption

Your grow light draws electricity to run the bulb and ballast. The sources can vary in wattage. From 50-watt NIR bulbs to 2000-watt LED or HPS setups. You can use multiple lights in series to boost your setup power capacity and meet the harvest requirements. Some lights have higher wattage than others. For instance, LED lights have lower wattages compared to halide lamps or HPS. Hence, these lights sources consume more power than LEDs, reducing the costs of running your indoor garden.

Lighting Footprint

Each grow light has a specific design to cover a garden area. Attempting to cultivate outside the light footprint can give poor results. The bulb’s wattage and its running height are two key factors to consider when deciding on the appropriate footprint for your indoor garden.

For instance, a 1000-watt bulb runs 3 to 6 feet above the canopy and is ideal for a growing footprint of about 3-square feet. When installing your grow light, make sure you follow the manufacture’s guidelines for the distance from a bulb to the canopy.

You can adjust these settings with small tests during your first harvest. It may take you the whole growing season to find the right system for your garden. Getting the appropriate placement to give optimal heat, intensity, and footprint requires time and testing.

Plant Photoperiods

Photoperiod refers to how much light you provide to your plants over 24-hours. When growing outdoors, you have a limitation of photoperiod. During the summer, you can get light up to 12-hours a day, while in the winter, it may reduce up to 6-hours a day.

However, when cultivating plants indoors, you can adjust the photoperiod to whatever wavelength you want. You can run a 24-hour photoperiod with constant lighting if you wish.

Heating and Cooling Effects of Grow Lights

Heat is one of the byproducts of running indoor grow lights. LEDs and CFL bulbs emit little heat during operation. Hence you are not going to notice any change in your growing temperatures.

However, HPS and MH lamps do emit significant amounts of heat. Hence, the light intensity generated by these bulbs may be higher, leading to an increase in temperature inside your growing space. The rise depends on the bulb size and your growing conditions.

To control this effect, you will need to set up fans or an air-conditioner to reduce the heat back to suitable growing temperatures.

How long do LED grow lights last?

Over time, all grow lights will begin to lose power and efficiency. A degraded lamp will not produce the needed light amount to have the best plant effect. Therefore, you will need to change lamps at least once a season to prevent degradation.

However, different bulbs types offer different service life, depending on the type, manufacture, wattage, and use in the garden.

Fluorescent Lights Degradation

Out of the many options in the market, fluorescent source degrades the least. These lights will lose about 10% of lumen capacity for every 20,000 working time hours.

LED Light Degradation

LEDs also have a low degradation rate. For instance, an incandescent lamp using filament lasts for about 6 to 9 months depending on your use frequency, while a LED will last for around 15 to 20 years.

Wrapping It Up

Grow lights are beneficial to indoor gardeners and can boost plants growth. While they don’t need to be on the whole day, they require monitoring for healthy and thriving plants.

There are many experienced gardeners out there willing to give free advice. Find recommendations of the best device brands to avoid making the same mistake most beginner gardeners make during their first season.

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