greenhouse lighting requirements

What Are The Greenhouse Lighting Requirements?

In Light by Ana M

Greenhouse requires light to promote crop growth and yield. Also, it plays an important role in photosynthesis. In summer it is crucial to provide enough shade for the plants. On the other side, in winter greenhouse lighting requirements change because low light along with low temperatures can cause plant growth to slow down.

How much light does a greenhouse need?

A greenhouse needs at least 6 hours of direct sunlight per day. To get the most of the sunlight site your greenhouse east to west, that way the largest side will get the most sun exposure. Make sure to keep the windows clean in winter. Remove the dust regularly as it is proved to increase the light intensity by 10%.

Do you need a grow light in a greenhouse?

Majority of gardeners rely only on natural light and don’t need a grow light in a greenhouse. However, if you plan to grow plants in winter, then you might need a grow light in a greenhouse. A grow light is an electric light which is specific to a light spectrum appropriate for photosynthesis.

Whether you need a grow light in a greenhouse depends not only on the time of the year but on the type of crops and how much sunlight is available.

You have to be very careful when choosing grow light for a greenhouse. The most common problems growers are running into include the lack of light, the light is of a wrong kind, the distribution of the light is not even or there might be too much of it.

What kind of light do you need to grow plants?

An artificial light to grow plants should provide a balance of cool and warm light that replicates the natural sunlight. That kind of light is perfect for flowering plants.

Depending on the type of the plant, stage of cultivation and photoperiod required, you will need a light with a specific spectrum range. A light spectrum is the collection of different wavelengths of energy produced by a light source.

greenhouse lighting requirements

In the visible spectrum of light, the color of light depends on the frequency. Different color of light helps plants to achieve different goals. When buying bulbs you can see the numbers 2700K and 3000K. It refers to the coolness and warmth of the light spectrum.

Plants need shorter, warmer wavelengths of light which are in the blue spectrum when growing and maturing. Alternatively, plants need longer, cooler wavelengths of light in the red and orange spectrum for blooming and production.

What Kind Of Lights Are Used In Greenhouses?

There are four types of lights that can be used in greenhouses:

  • Incandescent light
  • High intensity fluorescent light
  • High intensity discharge (HID) light
  • Light emitting diode (LED) light

Incandescent light bulbs for greenhouse

Incandescent light bulbs are electric lights which heats up to a temperature high enough to make it glow with visible light. Because of the heat they produce you must not place them close to foliage. It is a good option to increase the day length.

Incandescent light bulbs for greenhouse

Unfortunately, they don’t provide sufficient light for most greenhouse applications. It is a very easy lighting option to install and it is a good source of red wavelengths.

High intensity fluorescent for greenhouse

In comparison to incandescent bulbs, fluorescent light is more efficient in converting electricity into light without waste of heat. The color spectrum of standard cool white fluorescent bulbs is high in blue and low in red. Although, they do provide a full white light spectrum.

High intensity fluorescent for greenhouse

A standard fluorescent bulb knows as T12 is sufficient for houseplants, starting seeds but is weak in light intensity. A narrower T5 provides three times more light than T12 and is in both warm and cold spectrum.

Fluorescent light is a good option for a greenhouse with low natural light. It is also suitable for the propagating areas or growth rooms. Large spaces can benefit from fluorescent bulbs efficiency.

LED light for greenhouse

LED lights are more expensive to purchase than fluorescent light but use half the electricity and last up to five times longer. Also, their light intensity is far greater and they come in full spectrum light. LED lights are small in size and are really easy to install.

LED greenhouse lights

Will LED lights help plants grow?

LED lights help plant growth because they maximize blue and red lights to provide a balance for plants. They don’t provide green and yellow light and only optimize the light spectrum appropriate for photosynthesis. LED lights are helpful in all stages of plant growth.

What light source is recommended for a greenhouse?

HID is a recommended light source for a greenhouse as it is very economical. Many growers opt for HID as the best lights to provide supplemental greenhouse light. These lights are very efficient at converting electricity to light and are good at increasing light intensity.

There are two types of HID:

  • High-pressure sodium (HPS) bulbs – these are rich in red spectrum and are used to promote growth and flowering.
  • Metal Halide (MH) bulbs – these provide more blue light and are ideal to support vegetative growth. Use them in the early phase of plant’s life. In comparison to HPS, their spectrum is more balanced.

However, there are two disadvantages with this light source. First, you need to install them on the large heavy ballasts which come separately from the light fixtures. These ballasts are quite bulky and take a lot of space, so it is not as practical as in comparison to small-sized LED lights.

Second, HID lights produce a significant amount of heat. Therefore, you need to place them 30-36 inches (76-91 cm) away from the plants which effects the lighting efficiency. Also, in comparison to other options, HID lights are more expensive to operate.

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