Pros and Cons of Vertical Growing

Eric Moody

Horticulture, Lighting Strategies, Vertical Farming | April 28, 2020

With the rise of so many LED luminaires being introduced into the market, we have seen trends shift towardvertical growing. This is because LEDs can be more energy/space efficient, and they do not produce the same radiant heat compared to traditional HID (high intensity discharge) technology –  therefore allowing your light source to be placed closer to your crop. Deciding how you will initially set up your grow, whether indoors, in a vertical system or a traditional greenhouse, can be a challenging task.  So, if you are struggling to decide whether a vertical or traditional horticultural grow system is best for your application, then let’s dive into the pros and cons of each.  Take note that this decision will not be the same for every application, as there are benefits over certain crops that will not work for others.   

What Crop are you Growing? 

The first factor to take into consideration is the type of crop you are growing.  Many food crops are already grown vertical in the sense that they are grown on a vinereaching 14 – 16 feet tall.  Crops like tomatoes, peppers and cucumbers use top lighting and sometimes incorporate interlighting to increase light levels in the lower regions of the crop.  This type of vertical growing is tried and true, so we will not cover these crops in this post.  When discussing vertical growing, we will look at multi-tiered racking systems for growing crops like leafy greens, herbs and cannabis, and compare the pros and cons of growing these crops on racking systems indoors versus in a greenhouse or an indoor grow with top lighting.  

This a traditional HPS luminaire set up in a greenhouse where lights are placed much further away from the crop

This article from Horti Daily suggests from the title “The 10 biggest advantages of vertical farming,” that it would lay out the top 10 advantages for vertical farming vs traditional greenhouse growing – but upon reading it, the article only compares vertical farming to field grown crops.  Nine of the advantages listed:year round production, unaffected by weather, minimize water usage, no pesticides, reduced transport costs, energy efficiency, safe work conditions and labor costs; are all benefits of growing in any controlled environmentwhether greenhouse or in a warehouse.  Only one out of ten advantages are truly worth discussing between growing vertically or not, and that is “better use of space”.  

“Better Use of Space”  

Better use of space is the #1 reason we hear from growers contemplating the move to a vertical racking system – especially in the cannabis market.  Something we used to hear all the time is:  “If I can remove all of the heat from 1000W HPS luminaires from my indoor space and utilize that four foot distance, then I could double my growing canopy within the same footprint and therefore double my production”.  Is this a true statement though?  For low growing crops like leafy greens and herbs, this is true since these crops tend to require a much lower light level for growing.  These crops do not produce “fruit” within a canopyso you can grow them in very tight proximity with racks being 12-18 inches apart vertically – so you can double, triple, quadruple your growing space with HortiLED Multi type lighting.   

Leafy greens can be grown efficiently with a vertical growing set up

For cannabis, it is a bit trickier as you are growing a larger bush type crop, not a low growing crop.  For a cannabis grower who is used to growing a large bush that produces a massive amount of bud, they may now find themselves re-thinking how they grow.  As we see with many who are growing vertically, they now must grow a smaller plant to compensate for the rack height and therefore may not produce as much yield per plant as they are used to.  This may even lead growers to decide which cultivars will be best suited for growing vertically, as some cultivars are naturally shorter and have fewer leaves, which will serve better in a vertical operation.   

The question becomes: “If I double my canopy, but produce less bud per canopy square foot, am I going to be more profitable or not?”  – This is a hard one to answer.  If you were to double your canopy size in one room, but produce 25% less per square foot of canopy, would you still be profitable? Let’s do the math on this:  If you currently produce 40g/sq. ft and have 1000 sq. ft of canopy space, then you produce 40,000 grams or 40 kilograms per 1000 sq. ft.  If you double the canopy in this room, but produce 25% less per square foot, then you will produce 30 kilos per 1000 sq. ftso 60 kilos per room when canopy is doubled.  That seems like a great increase as your overall production just rose by 50%!  But does this make you more profitable?  Lets look at the infrastructure costs next. 

Costs to Go Vertical 

Above, we demonstrated that even with a decrease of 25% production per canopy square foot, we were still able to increase production of 1000 square feet by 50%.  If you are making the switch to LEDs from HPS in order to grow vertically, then you may also be thinking of the electrical savings you might have.  Currently, the closest replacement for a 1000W HPS is a 600W LED.  That is a savings of 40% for power, but since you need to double the lighting in your space for two tiers of vertical grow, this works out to be around 20% more wattage in your room (at minimum).  The question to think about becomes – do you have enough power available?  And does the 20% increase in power consumption eat up a large portion of the 50% increase in production?  

Another aspect to consider, is that there is a direct correlation between watts and BTUs (for more on this check out our blog on HPS or LED for cannabis). Therefore, the 20% increase in watts is also a 20% increase in cooling, so you should also be thinking about if you have the cooling capacity in your current setup or what will that cost be in a new grow installation.  

Cannabis in a vertical grow operation is best suited to 2-3 vertical racks because of the large size of the plant

The cost of the luminaires you purchase should also come into consideration.  A crop like cannabis is a high light level crop, so you need to use an LED that can deliver equivalent light levels of a HID luminaire.  The current market is that per µmol delivered to the crop, LED lighting can be 3-4 times more expensive than HPS.  If you spent $15,000 to light 1000 sq. ft of canopy with HPS, you would need to spend at least $90,000 on LEDs to light the 2000 sq. ft of tiered grow space.  When you combine this with the additional costs of racking, fertigation, etc. the increase in production starts to lose its value quickly.   

Example: 

If you are selling your bud for $800 per pound and were producing 88 lbs. per 1000 sq. ft of canopy (40 kg), thus making $70,400 for every 1000 sq. ft but then, after switching to a tiered system that was producing 50% more, you will now be selling $105,600 per 1000 sq. ft.  With this math you will need two full years of production to recoup just the added cost in lights alone.  If you were to compare this 1000 sq. ft of indoor space to that of a greenhouse, the cost difference becomes greater, since the greenhouse will use less artificial light because of the free natural sunlight from outside. 

Why 50% increase and not 100%?  

You may ask yourself why you wouldn’t produce 100% more product by doubling your canopy square feet.  This is a valid question and the reason is more than just a smaller plant that produces less bud as stated above.   

This 50% number has been thrown around for a few years now, like in this article. They probably did increase production by 157% as stated, but this article can be deceiving in some of the benefits it claims.  Yes, there was a decrease of 40% of power per luminaire, but then doubling the lighting in the room is still an increase of 20% of watts and BTUs in the space.  It is also stated that they reduced HVAC by 35% per sq. ft of canopy, but this is still an increase of 30% in the same room since the canopy is doubled.  And while the decreased cycle time of 25% looks appealing, it comes at the cost of 25% less production per canopy sq. ft.  The statistic that pops out the most when you read this, is the claim that the cost to produce per pound was reduced by 75%.  This is obviously hard to quantify as we do not know what this is being compared to.  Looking at the capital costs laid out above, if this is measured against a standard grow room using HID luminaires, then it may be hard to believe this number but since we do not know what the comparable iswe cannot quantify it. 

Factors Causing Less Yield per Canopy Sq. Ft  

There are a few other factors that contribute to the lower yield of cannabis per sq. ft of canopy than just limiting plant size or the cultivar being grown.  As stated in a previous article “There is a big misconception in the cannabis industry stemming from the LED suppliers that the ability to have your LED lights so much closer to your crop will help increase production lower into the crop. This could not be further from the truth! When your light source is closer to the top of the canopy then the shadows created from the top layer of leaves are much bigger than if the light was further away. Also, light penetration into the crop comes from the crossover between luminaires.”  Therefore, when your light source is close to your canopy, you are not able to penetrate light into the crop as deeply. This is because LEDs lack a reflector, which HID luminaires use to uniformly direct light, delivering a much wider range of illumination deep into the canopy  

Due to the lack of radiant heat – LED luminares can be placed much closer to the crop than HID luminaires

Besides lighting, the environmental conditions in a vertical grow can be quite complex.  The cannabis plant needs good airflowenough to create movement of the branches to grow a sturdy, healthy plant. So, when you grow vertically, it is harder to keep good air movement around your crop.  With this comes more complications, resulting from small microclimates that can form within the same room.  This can cause different levels of temperature, humidity, and CO2 levels within the same space.  Most growers who have made the switch to a multi-tier system, have also had to add more extensive sensors and controllers to help offset these issues, which also adds to the cost of the operation.  Just like with lighting costs, these factors are increased even more when comparing an indoor multi-tier grow to a greenhouse.  A professional greenhouse grower understands that the taller the greenhouse, with more open air space above the crop, the more stable and easier to control the environment, than is a small space.  This is because the slightest change in HVAC, humidity, or CO2 in a small space changes the overall environment much faster than in a larger greenhouse.  This can be very challenging for the indoor grower to monitor and control.  Think of it like comparing a bathtub full of water to a pool.  One gallon of hot water will noticeably change the temperature to a tub of water but may not be noticed at all in a pool full of water. 

Why Grow Vertically Then?

After reading this you may seem apprehensive about growing vertically but leafy greens companies like Plenty and AeroFarms appear to be making it work and moving forward.  As stated above, these growers are growing leafy green crops that do not produce fruit and don’t require a high light level to grow.  These are the perfect crops for growing in a multi-tier system as they do not need as much vertical space.  With leafy greens and microgreens, you can achieve good results with 4-6 tiers of crop – where you may only be able to achieve 2 tiers of a bushy plant like cannabis.   Below you can see how you can achieve many layers of greens production vertically – using either LED or HID lighting technology.  

LED or HID luminaires can be used to grow greens in a vertical racking system


In summary,
 vertical growing can be a great resource for feeding an evergrowing population by utilizing indoor spaces more efficiently for space efficient crops like greens.  While we’ve seen a boom in bringing this technology into the cannabis market, we are also seeing as many growers move away from this.  In a recent trip to southern California, we toured many traditional indoor grows within the L.A. area that all talked about removing their HID lighting and switching to a vertical grow system with LEDs.  We also toured many vertical operations that have been in business for a while who explained that, with the current downward trend in wholesale pricing, they are looking to get out of their indoor operation and want to move east toward Desert Hot Springs and Palm Springs where they can build a greenhouse in the desert to utilize the power of the sun, while still being in close proximity to their customers. 

The bottom line is that many LED manufacturers are doing a great job in depicting the benefits of growing cannabis vertically, but we advise you to add up the costs and run your true ROI numbers before jumping into such a complex endeavour for a complex plant like cannabis.