Broadside Lighting Garden

By Tim Walker

The Broadside Lighting Garden is a popular solution for many large scale growers. The combination of its simple set up, excellent light coverage and economical start up cost has helped it to become so widely used. We will set up a hypothetical garden using these techniques, and attempt to explain the various tasks involved in creation and upkeep.
For this example we will assume we are dealing with a grower who is using Broadside lighting to grow three gallon-size plants in peat moss or coconut fibre. His production area contains 120 plants in an area of 15 feet by 20 feet, making an overall size of 300 sq ft. His crops will be spending eight weeks in this production area, and we will assume he starts new plants in half his flower area every four weeks. With this being true, he will need 60 rated cuttings every four weeks. To support this garden, our grower will need a propagation area, a green area and two production areas.

The first stage of his operation will include his propagation room, the nursery of his growing area. Here, his cuttings will receive a little specialized attention to ensure their strength and adaptability. For this area, he should have two four-foot fluorescent lamps suspended above two propagation trays. This will allow for 70 cuttings every four weeks. This gives our grower a failure margin of ten plants per rotation, so that he can keep up with his optimum volume.
Starting plants from stem cuttings is known as asexual production, or cloning. The major benefit of cloning is that our grower's plants are a complete genetic duplicate of the mother plant. So, our grower has already given his new plants a leg up by giving them such a solid genetic foundation. When cloning, there is a blueprint our gardener follows to ensure a healthy future for his plants:

1. He uses a clean, sharp blade to cut off a small branch consisting of a growing tip, two or three leaves, and 2" to 4" of stem.
2. As he takes the cuttings, he lets them stand in water until he has all 70 of them. He lets them soak as he prepares his propagation media.
3. Our gardener ensures that his propagation media is sterile and pH balanced. He chooses rockwool because of these considerations.
4. He then uses a diluted, high phosphorous solution to saturate the medium (rockwool cube) and places it in his propagation tray.
5. Now, it is time for him to apply the rooting hormone. He first makes a small, fresh cut just above the original cut on each stem right before dipping the cutting into the hormone. He dips about ¼" of stem into the compound, ensuring there is adequate coverage. Now, he inserts the stem into the grow medium deeply enough to ensure stability.
6. Once all of the cuttings have been transferred to the individual trays, he covers them with a clear plastic dome to retain humidity.
7. The optimum light cycle for this stage of our growers plant's development is 18 hours, so he sets up a timer for his lights to keep this schedule.
8. To allow fresh oxygen for his plants and to avoid damping off, our gardener removes the clear plastic cover for a few minutes each day.
9. While airing out his plants, our gardener mists them with a mild foliar feed. In this instance, he has chosen kelp extract. He also occasionally checks them to see if their roots have taken hold. Gingerly grasping the stem and giving it a short tug, the resistance will eventually show him that the root system has begun to weave successfully with the grow media.
10. Our gardener pats himself on the back and heads for the nearest Pub. He has done a great job, but its not over yet!

It can take anywhere from one to two weeks for a clone's root systems to have developed adequately enough to move onto the next stage. Carefully monitoring his crop through this time has allowed our grower to move onto the next stage of development.

The next area in a garden of this size is the Vegetative or Green Growth Area. This area is an intermediate area with a two-fold purpose. It directly supports the propagation area behind it and the production area ahead of it. Our gardener will be relying on the plants in this area to supply the 70 cuttings that he will need to replenish his propagation area every four weeks. Also, these donor plants will be moved through the cycle to the production area to further their growth to maturity when the time is right. With a little bit of patience and know-how our gardener can make his garden completely self-sufficient!

You may think this sounds like an easy task, but it takes a little bit of planning. Our gardener has 60 plants to cultivate 70 cuttings for the next four week cycle. However, our gardener has to work out a simple schedule to learn how big his green area plants will be when it is time to acquire his cuttings. If his schedule shows him he would need to take his clones from very small green area plants (ie: First week of green growth stage), he may have to adjust his crop size to allow it. Since his donor plants will be so small, it would be hard to take more than one cutting from each plant. To solve this, he would have to add extra stock plants to his cycle to ensure enough cuttings for future generations.

To illustrate this cycle, we will use a flow chart to see the most economical way to arrange our crop rotation.

The cuttings in our growers garden are spending weeks one and two in the propagation room, then they're moved to the green room for weeks three through six. Finally, they are moved to the Flower (Production) Room for the last eight weeks beginning in week seven. By drawing up a quick flowchart like this, it is easy to see the most time effective method of setting up the crop rotation. Looking at the chart you can see that the best time to start the propagation of crop two will be during the ninth week of the first crop. At this point, the crop one plants will be entering their third week of green growth, so will be advanced enough to supply the desired number of clones.

Our grower has thought ahead by adding a second production, or flowering, area. Since this is the most time intensive of the three stages, by adding a second area he can make much more economical use of his time. As you can see, with only the one production area, our grower could expect to harvest two crops in 22 weeks, but by adding a second production area, he doubles his output in only four more weeks! This is evident in the following flowchart.

Since the second flower area will start four weeks after the first, we need "Target Size" green plants to start flowering in this area for week two. Allowing four weeks green growth for these plants, our grower has learned that his plants must start in the green room in week seven, and because of this, he will need his cuttings to be ready at the beginning of week five. The garden is running at peak efficiency at this point, and is relying on the grower's diligence to stick to the prescribed formula.

Now, our grower has his growing schedule worked out, and his propagation begun. Since the ball has begun rolling, he needs to figure out the layout of his green room and production areas since they will soon be in use.
The grower designs his Green Area to support his prescribed time cycle. To do this, he needs 60 "Target Size" plants ready every four weeks. To accommodate this size of crop, he will need at least 90 sq ft. The lighting needs for this stage are much more demanding than those previous, so he has installed two MH1000 lamps with parabolic hoods. Although a light mover such as a vertical track or radial arm could increase his light coverage and equalize its effects, he opts to go without this time. It may be a future purchase, but for now, he is trying to keep it simple by sticking to his original idea: the Broadside Lighting Garden. He has used a light meter to ensure all areas of his garden are receiving adequate light, and has set up a timer to regulate the light/dark cycle for his plants. He determined the optimum light cycle for this stage by asking the clerk at his favourite hydroponic gardening supply store. The difference is sometimes negligible, but some crops prefer a slightly different light cycle than others.
His two production, or flowering, areas have been designed exactly the same as each other. They will be serving exactly the same purpose, the only difference being the times they are in use. These production areas will be harbouring 60 "Target Size" plants every eight weeks, and to accomplish that will need a minimum of 150 sq ft. He has installed four HPS 1000 watt lamps without shades. The high pressure sodium lamps will provide a much more efficient light spectrum than the metal halide for this growth stage. While working on his plants in both the green growth and production areas during the "daylight" cycle, he wears a pair of sunglasses to protect his eyes from the intense light. There is a difference in layouts between the Green Growth and Production areas. In the Green Growth area, the bulbs were suspended directly above the crop area using parabolic reflectors to diffuse and direct the light to the entire crop. In the Production area, however, the bulb is suspended with the tip of the bulb parallel with the mid-point of the "Green Zone". The plants are set up in steps ascending in height as they move away from the bulb. Our grower measured the distance from the base of the lowest plant to the top of the highest place plant. This measurement is the "Green Zone", and directly in its center is where the tip of the bulb should be elevated.
To "step" your plants so they ascend in height as they travel further from the light source, there are many options. Our grower chose to use cinder blocks and planks for his flowering area.
The Broadside Lighting Garden has one drawback from its "stadium" style set-up. Because of the orientation of the lamps, the plants will receive direct lighting on only one side, the side which faces the bulb. To solve this problem, our grower regularly turns the individual pots so that the entirety of each plant gets the same amount of light to "drink". He found out by asking, that through trial and error, the best formula for pot rotation is to give each pot a 1/3 turn every second day. Aside from improving the exposure of his plants, rotating the pots also helps lower the risk of infestation. Since there is no weak poorly-lit foliage, mites are not as attracted to the plants as they would be otherwise. To make the job easier on himself, our grower marked lines on the outside of his pot segmenting it into 3 equal parts. He also painted an arrow pointing clockwise on the outside. This helps him to remember the direction and degree of rotation that is needed every second day. Not the theory of evolution this, but it definitely simplifies our grower's day.
If you are looking at setting up a large garden on a small budget, the Broadside Lighting Garden may be the right choice for you. It definitely worked for our grower, he is already back in the pub.