The Hidden Cost of a Packed Greenhouse

The Problem

The idea that “more plants = higher yield” is a common thinking trap we see even the most experienced growers fall into. While it seems logical, it’s a dangerous thought that could potentially ruin your harvest. 

It all comes down to light. Too many plants, too close together, start to compete for light. In the process, they shade each other, become stressed and end up reducing the very thing you’re after – quality and yield per plant.

Overcrowding also increases the humidity, which increases the risk of disease. Think of it like a crowded room: the more people you add, the less comfortable it gets, and the faster disease can spread.  

It’s also not the right financial call. Higher density often means higher costs because there’s more starter material, more fertiliser, more labour, etc. And if each plant produces fewer, lower-quality fruit/berries/leaves/etc, that means fewer saleable crops at a higher production cost. The numbers just don’t add up.

The Solution

Over the 30+ years of turnkey greenhouse engineering for hundreds of clients, we’ve found (at least) one thing to be true:

Getting a high yield isn’t about cramming in plants. It’s about intentionally designing the space between plants to optimise light and airflow for that specific crop.

Why this works

Different crops require different spacing strategies because their needs for light, room to grow, and airflow vary significantly. The right density depends on the crop, greenhouse design, and climate.

This isn’t guesswork. There is a science and method to finding optimal density. Finding that sweet spot takes experience and agronomic expertise. Over the years, we’ve run density trials across dozens of crops in different structures and climates. That work has given us the data to know when closer planting pays off and when it doesn’t. Here are a couple of examples.

Peppers: When Closer Works

In high-tech greenhouses, you might be able to plant more than you initially think. For example, at Emseni, we designed for seven rows per bay of peppers instead of the standard and typical six rows in a 9.6-meter greenhouse span.

Row spacing and pathways between plants were smaller, but trellising and advanced climate control kept light penetration strong and humidity within limits. We proved higher yield per square metre and more Class 1 fruit. But this was only possible because of a peppers’ upright growth and high-tech house with the systems to manage and protect the crops very effectively.

Strawberries: When More Space Wins

To perform their best, strawberries need room to spread and grow. When they’re crowded, the lower canopy gets shaded, fruit stays small, and Class 1 percentages drop. With more space, airflow improves, light reaches every leaf, and yields hold up with higher quality fruit – even with fewer plants.

In strawberries, too many plants in the space means less marketable yield. Push density too far here and you lose on two fronts: more labour and disease pressure, and less fruit per plant.

Medical Cannabis: Depends on Your Budding Goals

Spacing is a constant discussion within the medical cannabis industry. The “right” density depends on the specific genetics of the plant, and goals for THC vs CBD production like how long you let plants vegetate, how tall you want them to grow, and how you shape the buds.

Because cannabis is highly sensitive to humidity, and requires precise light control, more plants can quickly reduce quality. Even small shifts in timing or spacing alter the microclimate and the quality of the end product. Here, spacing isn’t just about rows and aisles. It has to be tuned alongside timing and plant management. Custom precision is what delivers results.

Why Work with Us

We didn’t invent the idea of optimised spacing. What we bring is the ability to make it work reliably, crop after crop, with our engineering and agronomy expertise.

We match design to biology and approach each project with fresh eyes. Because we design greenhouses from the ground up, we can build in the flexibility of row spacing, aisle width, trellis height, and irrigation options that each crop and goal demands.

By designing your greenhouse with this approach, you’ll unlock more yield per square metre, often with fewer plants.

If you’d like to find out more, we’d love to chat to you on +27 21 987 6980 or info@vegtech.co.za.