Tyler Simmons (Technical Expert at Front Row Ag) and Egan O'Keefe (Co-Founder of Front Row Ag and Director of Cultivation at Story) dive deep into the critical aspects of optimizing Controlled Environment Agriculture (CEA) cultivation. They explore the intricacies of plant spacing, canopy density, and trellising techniques, providing valuable insights for growers looking to maximize yield and quality.
Topics Covered:
00:20 - Optimizing usable flower sites per cubic foot
01:43 - Balancing plant size, veg time, and plant spacing
02:24 - Issues with high planting density and large plants
02:47 - Shade Avoidance Response
04:04 - Balancing veg duration and plant spacing
05:06 - The cubic canopy
05:17 - Calculating veg time per square foot for crop rotation
05:27 - Unique considerations for vertical facilities
06:17 - Trellising and plant training during the stretch phase
08:01 - Optimizing bench space utilization
08:39 - Branch density and trellising techniques
10:12 - Selective pruning and defoliation
11:12 - Balancing trellising, plant spacing, and canopy density for maximum yield and quality
11:44 - Consequences of improper planting density
Tyler and Egan offer practical advice and rule-of-thumb calculations to help growers achieve the perfect balance in their cultivation practices. They discuss the importance of considering factors such as strain vigor, growth rates, and facility design when developing an optimization strategy.
Transcript:
When we optimize a cultivation facility, there are high-level goals many teams overlook. The big one: maximize the number of usable flower sites per cubic foot across the entire canopy—not just per square foot.
Over the last decade, room design evolved from lighting only the tray surface to lighting the entire room, reclaiming wasted aisle space with rolling benches. Then we pushed into the third dimension—optimizing canopy depth—helped by higher-intensity LEDs that deliver greater PPFD and deeper penetration. The target is simple but powerful: more usable flower sites per cubic foot.
A “usable” flower site meets a minimum PPFD threshold at its position so it can produce quality. That means two things must be tuned together:
-
Light distribution/penetration (room, fixture, and trellis strategy), and
-
Plant architecture (size, veg duration, spacing, and branch density).
Getting Plant Size and Spacing Right
There’s no single perfect recipe, but there are many wrong ones. If you choose high planting density (e.g., ~1 plant/ft²), plants must be smaller with shorter veg. If you use lower density (e.g., ~1 plant/2 ft²), plants need longer veg to achieve the same productive canopy volume.
A common mistake is packing too many large plants too close together. When plants overgrow each other, shading increases, red:far-red balance shifts in the lower canopy, and you trigger shade-avoidance stretch. Instead of creating tight internodes and lots of sites, plants waste energy on elongation, resulting in fewer sites per cubic foot and poorer light at depth.
On the flip side, if plants are too small or too sparse, photons hit benches instead of leaves—wasted photosynthesis and lost yield/quality. The solution is to balance veg duration with spacing.
Rule of thumb: plan ~5–7 days of veg per square foot of canopy the plant will cover.
-
For ~1 plant per 2 ft², that’s typically 10–14 days of veg (sometimes ~10 days for very vigorous cultivars).
-
You want the canopy fully filled at the end of stretch—not a week into stretch, and not weeks after.
Facility Constraints & Vertical Racks
In multi-tier rooms with tight vertical clearance (e.g., ~4.5–5 ft from bench to fixture), veg time may need to be shortened to stay within finished height limits. Trying to force a third or fourth tier can become labor-inefficient and compromise yield per tier. Less can be more.
Trellising, Canopy Fill & Small Daily Touches
Trellis timing matters. During stretch, spend a few minutes every day or two guiding branches into empty trellis squares—not weaving, just gentle spread. Look straight down from the fixture: fill the biggest gaps first. This quickly improves branch density uniformity, raises the share of sites at target PPFD, and often reduces later pruning work.
Aim for a productive canopy depth (often ~30–36 in at the top). Below the productive depth, clean up lower growth. In the productive zone, selective defoliation (especially upper half) helps light reach sites below, while leaving leaf area in the lower half captures remaining photons. Take only the leaves you need to open light paths—don’t overstrip.
If planting density is too high for plant size, you’ll pay for it in labor: more branch removal, more leafing, deeper lollipopping, and longer pruning passes.
Avoiding “Swiss Cheese” Canopies
In vertical systems (e.g., 4×8 sections ≈ 32 ft²), you’ll sometimes see multiple 6×6 in “holes” with no sites—often 3–4 ft² of unused canopy from sloppy spacing or missed trellis timing. That’s ~10% of the canopy gone—huge when measured in grams/ft². Standardize rows, align pots, pull to the bench edges, and fill that “side wall” of the canopy so photons aren’t wasted.
Special Cases: Plant-Count Limits
If regulations cap plant counts and you’re forced to fill a large footprint with fewer plants, you may need longer veg, more topping, aggressive training, and careful scrog work. It’s workable—but your planning still revolves around:
-
Optimal veg time for the footprint,
-
Trellis timing and daily micro-adjustments, and
-
Pruning strategy (what stays vs. what goes) to keep all remaining sites productive.
