FIELD OF THE INVENTION

The invention relates to a luminaire that is used for growing plants in an indoor environment and which includes an array of light emitting diodes (LEDs) as a light source. The invention extends to a method associated with such use of the luminaire.

BACKGROUND OF THE INVENTION

The spectrum of light relevant to growth and development of plants ranges between 300 to 800 nanometers (nm). Far-red radiation or light can be defined as photons with wavelengths from 700 to 800 nm. Sunlight includes almost as much far-red radiation as red light. This far-red light is barely visible to humans.

Plant leaves effectively absorb red light but reflect or transmit most far-red light. Plants perceive this filtering of light and stimulate growth intended to avoid shade and capture available light. This phenomenon may be referred to as “shadeavoidance response”. Far-red light accordingly has a marked effect on extension growth of plants. This may influence branching and the size and elongation of stems and leaves. Far-red light may also promote flowering in some plants.

The Emerson effect refers to an increase photosynthesis rate when chloroplasts are simultaneously exposed to light of wavelength 680 nm (deep red spectrum) and of wavelength more than 680 nm (far-red spectrum). The exposure to both wavelengths results in a rate of photosynthesis that is significantly higher than the sum of the red light and far-red light photosynthesis rates. The effect was discovered by Dr. Robert Emerson and provided evidence of cooperation in photosynthesis where two photosystems are processing different wavelengths. There is a significant market involving the indoor cultivation of cannabis crops particularly for medicinal applications. This involves providing the appropriate overhead lighting. The industry will benefit from any improvements that can be made to growth cycle gains and intervals and/or chemical yields of tetrahydrocannabinol (THC) and Cannabidiol (CBD).

OBJECT OF THE INVENTION

It is an object of this invention to provide an LED luminaire used for growing plants and a method associated with such use, wherein the features of the invention enable benefits at various stages of plant growth through the inclusion of far-red radiation in horticultural lighting. The invention preferably applies to the indoor growing of cannabis.

SUMMARY OF THE INVENTION

In accordance with the invention there is provided a horticultural luminaire which includes: a housing with at least two arrays of light emitting diodes (LEDs); a first array comprising white (or full spectrum) light emitting LEDs and a second array comprising far-red light emitting LEDs; in which the first LED array is provided with a first electricity supply circuit and first LED driver and the second LED array is provided with a second electricity supply circuit and second LED driver; the first LED array and the second LED array to be independently operated at different times or at the same time to provide light emission profiles selected from:

(i) a first light emission profile (W) comprising separate white light without far-red light when only the first circuit is activated; (ii) a second light emission profile (FR) comprising separate far-red light without white light when only the second circuit is activated; and

(iii) a third light emission profile (W/FR) comprising a combination of white light and far-red light when both the first circuit and the second circuit are activated.

The invention further provides for the luminaire to include a third array comprising LEDs that emit UVA light, in which the third LED array is provided with a third electricity supply circuit and third LED driver, and for the third LED array to be independently operated to provide UVA light as part of the first light emission profile, as part of the second light emission profile, as part of the third light emission profile and/or as a fourth light emission profile (UV) comprising separate UVA light without white light or far-red light when only the third circuit is activated.

Further features of the invention provide for a separate switch to be provided in a live wire of each power supply circuit; and/or for the power supply circuits to be connected to a control apparatus that is programmable to provide a selected light emission profile at a required schedule.

In accordance with another aspect of the invention there is provided a method of providing indoor light to grow Cannabis plants, which includes: use of a luminaire as defined above; and independently operating the first LED array and the second LED array at different times or at the same time; to provide light emission profiles selected from:

(i) the first light emission profile (W);

(ii) the second light emission profile (FR); and

(iii) the third light emission profile (W/FR); with the purpose of exposing the Cannabis plants to a suitable light exposure regimen based on a growing stage of the Cannabis plants. In accordance with a further aspect of the invention there is provided a method of providing indoor light to grow Cannabis plants, which includes: use of a luminaire as claimed in claim 2; and independently operating the first LED array, the second LED array and the third LED array at different times or at the same time; to provide light emission profiles selected from:

(i) the first light emission profile (W) with or without UVA light;

(ii) the second light emission profile (FR) with or without UVA light;

(iii) the third light emission profile (W/FR) with or without UVA light; and

(iv) the fourth light emission profile (UV); with the purpose of exposing the Cannabis plants to a suitable light exposure regimen based on a growing stage of the Cannabis plants.

The invention further provides for the features of the method to include further features of the luminaire defined above and/or aspects of the light regimens referred to in the description below as achieved by suitable operation of the luminaire.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described, by way of example only, with reference to the specific embodiment of the accompanying drawing:

Figure 1 which shows a bottom side view of a schematically illustrated horticultural luminaire and electricity supply circuits.

DETAILED DESCRIPTION OF THE INVENTION

Cannabis plants have growth stages. The different stages require different amounts of nutrients, water and light. The latter is relevant to the current invention - specifically in the context of an indoor growing environment which will preferably be on a large commercial scale to supply a cannabis crop for use in the medicinal use industry. (This specification does not deal with supply of nutrients and water.)

It can take from about 3 to 8 months to grow a cannabis plant from seed to the time of harvesting. One way to accelerate the cycle is by starting with a clone.

A cannabis clone is a cutting from a living plant which is treated with a hormone to develop roots. The plant from which it was taken is called a mother plant. The use of clones avoids the seed germination phase. Once the clone has developed roots it can be planted as a seedling.

The more significant variability in growth cycle time for a cannabis plant occurs in the vegetative stage, which follows the seedling phase and occurs before flowering. When growing outdoors, the crop is seasonal and the plants start to flower with the shortening of days in autumn. Indoor growing allows for a cannabis plant to be induced into the flowering stage through artificial light control. This may take place after only a few weeks or after several weeks. The duration of the vegetative stage will affect the size of the plant that is taken to flower.

Referring to Figure 1 , the invention provides a horticultural luminaire (1 ) which includes a housing (2) with at least two arrays of light emitting diodes (LEDs). In this embodiment, there are three arrays of LEDs (3; 4; 5). The luminaire will be used in a hydroponics growing room.

Each array (3; 4; 5) is provided with a separate power supply circuit (6; 7; 8) having a live (L) and neutral (N) line for independent wiring of each power supply circuit to an electricity supply. The three circuits (6; 7; 8) are also wired to control apparatus (not shown), which will be of suitable electronic type. More specifically, a first array comprises white light emitting LEDs (3) and a second array comprises far-red light emitting LEDs (4).

The arrangement provides for a luminaire wherein:

- The white light LEDs of the first array (3) provide full spectrum white light and the second array (4) emit far-red light at 730 nm; and

- The first LED array (3) is provided with a first electricity supply circuit (6) and first LED driver (12) and the second LED array (4) is provided with a second electricity supply circuit (7) and second LED driver (13).

The first LED array (3) and the second LED array (4) will be operated independently by the control apparatus which powers the LED arrays at different times or at the same time to provide light emission profiles selected from:

(i) a first light emission profile (W) comprising separate white light without far- red light when only the first circuit is activated;

(ii) a second light emission profile (FR) comprising separate far-red light without white light when only the first circuit is activated; and

(iii) a third light emission profile (W/FR) comprising a combination of white light and far-red light when both the first circuit and the second circuit are activated.

The third array (5) comprises LEDs that emit UVA light at 395 nm and is also provided with a separate, third electricity supply circuit (8) and third LED driver (14) for independent operation by the control apparatus. This operation of the third LED array (5) provides for UVA light to be part of the first light emission profile, the second light emission profile and/or the third light emission profile. Alternatively, a fourth light emission profile (UV) is provided which comprises separate UVA light without white light or far-red light when only the third circuit is activated. A separate switch (9; 10; 11 ) is provided in the live wire (L) of each power supply circuit (6; 7; 8). The three switches are connected to the control apparatus which will enable operation of the luminaire to achieve the results referred to below. (In a simplified version of the luminaire, each switch may be manually operated by a user.)

During the Vegetative stage of the plant, the objective is to be able to create a canopy that covers as much of the space as possible. This growth serves to maximize use of the light source provided by increasing the size of the plant to receive light. The faster the canopy can be created, the sooner a grower can switch the plants to the flowering stage, shortening the overall growth period. Far- red light is not used in the vegetative cycle.

Switching to the flowering stage involves changing the light cycle to 12 hours of daylight and 12 hours of night. Using the far-red light with the full spectrum white light for the first 2-4 weeks (dependent on the strain) will increase the rate of photosynthesis and increase the stretch in the plant.

During the mothering growth cycle of a cannabis plant, the plant needs full spectrum white light for a cycle of 18 hours of day and 6 hours of night. This ensures the plant remains in the vegetative cycle. It is recommended that 2 weeks before cloning, far-red light is switched on with the full spectrum white light This will cause the plant to stretch which will result in more opportunity for cloning.

The far-red light is not used during the cloning period. This is the period from the time that the clone is cut from the mother plant and during which it grows roots for planting as a seedling.

The invention further provides for a method of providing indoor light to grow plants, which includes the use of the luminaire in Figure 1. This apparatus uniquely provides three circuits respectively for the three LED arrays, which allows a user to easily operate the three LED arrays in a manner that provides the various light emission profiles referred to. The method of the invention involves providing one or more of a grower to select alight exposure regimen as desired or required by that grower and a particular variety of Cannabis. The different circuits of the luminaire allow for the provision of full spectrum white light, far-red light on a separate circuit, and/or UVA light on a third circuit. The circuits can be used separately or in conjunction to allow a grower to implement the following growth advantages:

(a) During a mothering stage of mother plants (to provide cuttings for clones):

- an approximate 18/6 hour light/dark schedule;

- wherein an 18 hour light cycle is comprised by the first light emission profile (W) - in other words, 18 hours full spectrum white only then 6 hours sleep;

- two weeks before harvesting of clones far-red light is switched on along with full spectrum white light. This will encourage the plant to stretch allowing for better clones.

(b) During cloning:

- Far-red light is not used in the cloning phase.

(c) During a vegetative stage: - an approximate 18/6 hour light/dark schedule is applied;

- with light in an 18 hour light cycle provided in accordance with the first light emission profile (W) - in other words, 18 hours full spectrum white light only then plant sleeps for 6 hours;

- Far red is not used in this stage.

(d) During a flowering stage of harvest plants: - an approximate 12/12 hour I ig ht/dark schedule;

- wherein a 12 hour light cycle is provided in accordance with the third emission profile (W/FR);

- more specifically, 12 hours full spectrum white light along with far-red light for the first two to four weeks only (dependent on strain) and thereafter full spectrum white light only until harvest.

When growing plants are in a vegetative stage and/or when the mother plants are in the mothering stage under the approximate 18/6 hour light/dark schedule, the 18 hour light cycle may: commence with approximately 10 minutes of the third emission profile (W/FR) to simulate sunrise; be followed by the first light emission profile (W); and conclude with approximately 10 to 15 minutes the third emission profile (W/FR) to simulate sunset. Alternatively, a grower may lower the W emission profile (instead of using FR) to simulate sunrise and sunset for half an hour to begin with and half an hour to end the 18 hour light cycle. The 18 hour light cycle period must not however be exceeded.

When harvest plants are in a flowering stage, the 12 hour light cycle may be followed by approximately 30 minutes provided in accordance with the second light emission profile (FR). The 30 minutes of FR needs to be within the 12 hour cycle and must not exceed the 12 hour light cycle.

The use of far-red light, whether by itself or with full spectrum white light, will not exceed the time cycle of the light (either 18 hours of day and 6 hours of night during the vegetative or mothering cycle or 12 hours of day and 12 hours of night during the flower cycle). Should the time be set to exceed these guidelines, the plant may be at risk of hermaphroditism due to inconsistent lighting schedules.

When mother plants are in the mothering stage, for about 2 weeks before cloning, the plants may be exposed to a third light emission profile (W/FR). The light treatment regimen options allow for a grower to provide Emerson effect increases in photosynthesis as well as side growth and leaf size benefits. There is also an evening of canopy if multiple strains grow in same room.

The far-red light serves to increase Photosynthetic Photon Flux Density (PPFD) and is used until 2 weeks before harvest.

The petalless flowers or buds for harvesting start to form at the beginning of the flowering stage. The plants can be harvested once buds have reached full maturation. As a further feature of the method of the invention, there is provided for the controlled use UVA light on flowering plants to the produce a response that is accompanied by production and/or migration of resin containing Tetrahydrocannabinol (THC). The desired result in an increased quantity of THC in the buds.

The method features of the invention enable an accelerated growth cycle through any one or more of the various stages. The luminaire of the invention enables a varied operation of the different LED arrays to achieve light emission profiles. The separate circuits allow for simple wiring and the operation may be automated by using programs and timers as required.

This method provides for shade avoidance and/or Emerson effect to be used in cannabis growth when combining the use of two spectrums together; far-red (at 730 nm) and full spectrum white (400-700 nm). Far-red is typically used because it regulates flowering, mediates stress and triggers “shade avoidance response”, which causes stretching and leaf expansion. The increase in leaf size allows the plant to receive more light, and thus can potentially increase overall growth. The stretching is caused because the top leaves of the cannabis plant receive most of the deep red light and transmit most of the far-red. Due to this, the lower leaves will receive more far-red than deep red and respond by elongating in order to find more light. The invention is beneficially applied to Cannabis sativa and Cannabis indica plants and both species may be farmed to provide a simultaneous harvest. A person skilled in the art will appreciate that a number of other variations can be made to the described examples without departing from the scope of the current invention.