Guide to Grow Sunflower Indoors with LED Grow Light

Sunflowers are regarded as the symbol of positivity. Their bright yellow flowers and tall stems evoke an aspiring and energetic feeling. Sunflowers are also known for their tilt heads that always track the sun before blooming during the day. Although outdoor sunflowers are able to absorb more sunlight, they are threatened by chewing insects and birds. Therefore, indoor growing is an alternative and safer option for sunflowers.

It goes without saying that light is critical for sunflowers. Light is the leading source of photosynthesis. LED growing lights, which are designed to mimic sunlight, provide an opportunity for indoor sunflowers to grow. Horti-King is one of the LED grow lights that is beneficial for indoor sunflowers. This post would like to talk about how to grow sunflowers indoors with Horti-King LED grow light.

Why use Horti-King LED grow light

As we all know, sunflowers grow best in full sun environments and they require high light levels. LED grow lights offer sun-like lighting for sunflowers indoors. Horti-King is a full-spectrum top lighting solution for sunflower plants. It helps to improve growth as well as achieve year-round production with the typically designed wavelength range that is beneficial for photosynthesis.

The efficacy of Horti-King is up to 2.8 µmol/J, contributing to reducing energy consumption and cutting electricity bills. Horti-King also has premium quality. Aluminum extrusion profiles enlarge the heat dissipation area and accelerate heat conduction, ensuring stable performance. No additional assembly is required as Horti-King is easy to mount and ready for installation. The simple installation and operation make it an ideal solution for achieving high and uniform lighting levels in greenhouse and indoor sole-source applications.

What is the right light intensity for indoor sunflowers?

Appropriate light intensity varied with the growing stage of sunflower plants. In short, high light intensity is helpful for sunflower growth. Low light intensity will cause disfigured morphology and decrease market value.

PPFD (µmol) is used for measuring the light intensity of grow lights generally. It means the photosynthetic photon flux density, which measures how many active photons fall on a given surface of the plant. But PPFD is changed with coverage area and height. To calculate the light intensity and manage the supplemental lights more precisely, DLI (Daily Light Integral) is introduced. DLI (mol·m-2·d-1 ) is the amount of PAR delivered per unit area during 24 hours. There are no additional requirements of light intensity during the germination stage. DLI ranged from 12 to 16 mol·m-2·d-1 is recommended for caring young plants. When the sunflower bud emerges, the DLI can be increased up to 20 mol·m-2·d-1.

How many hours should indoor sunflowers be illuminated?

The illuminated hours for indoor sunflowers are related to the photoperiod of sunflowers. Photoperiod refers to the time that plants are able to receive light in 24 hours.

Plants are classified as long-day plants, short-day plants, and day-neutral plants. Long-day plants initiate flower when the photoperiod is long (duration of day length longer than night length). In contrast, short-day plants will flower when day length is shorter than night length. Day-neutral plants, however, do not have a response to the photoperiod.

The growth and development of most sunflower cultivars are affected by photoperiod. ‘Frilly’ is one of the long-day sunflower cultivars. ‘ProCut orange’ and ‘Sunrich gold’ are short-day plants. ‘Soraya’ and ‘the Joker’ are nay-neutral plants. Specific illuminated hours for indoor sunflowers should be scheduled according to the cultivar of sunflowers. For example, a photoperiod less than 12 hours is positive to promote flowering for short-day sunflowers.

The photoperiod should also be arranged by the growing stage of plants. Supplemental lighting is not required during the germination stage. Since most sunflower cultivars are long-day plants, a photoperiod of more than 13 hours but shorter than 20 hours can improve flowering.

What to do when natural photoperiods do not match sunflower growth

The photoperiod is essential to the development of sunflowers. If natural photoperiods do not match the growth of sunflower plants, we should take actions to adjust the duration of ‘day length. ’ If the natural photoperiods are too long, we can shorten the photoperiods by blocking out the light that shines on the sunflowers. Black covers with plastic or cloth material are generally used to protect against natural light. After the covers are pulled over the sunflowers, we should pay attention to the small gaps where light is able to light the sunflowers.

But this activity may cause heat accumulation, which can kill the plants. To avoid heat accumulation, we can choose aluminum shields to reflect the sunlight. We can also pull the covers before sunrise. Because the temperatures before sunrise are lower, there is less possibility to accumulate heat. If natural photoperiods are too short to initiate flowering, we can extend the photoperiods by delaying the time of lighting or breaking up night lighting. For example, when the natural photoperiod is only 10 hours, we can supplement 3 hours of lighting after sunset to achieve a 13-hour photoperiod.

The lighting recommendations for indoor sunflowers (long-day plants) are as follows:

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