Living partnership: Bacillus and Trichoderma in greenhouse systems.

In nature, strength doesn’t come from sameness — it comes from collaboration. The most resilient ecosystems are those built on diversity: species that differ wildly in form and function, yet come together to support the whole. In greenhouse agriculture, that same principle applies below the surface. Microbes like Bacillus and Trichoderma may come from different biological kingdoms — one bacterial, one fungal — but when used in tandem, they form a living partnership that mirrors the very ecosystems they evolved in. Different in biology, united in purpose, these microbes offer growers a powerful, natural way to support root health, suppress disease, and improve crop performance in the most controlled environments on Earth.

In greenhouses, every square foot counts — and every crop needs to thrive in a tightly controlled, high-output environment. That’s why greenhouse growers are increasingly turning to biology as a partner in plant health. Though they have different niches, Bacillus bacteria and Trichoderma fungi have something important in common: they protect plants, support growth, and help growers reduce reliance on and costs of synthetic inputs. When used together or in rotation in the greenhouse, they form a powerful partnership that enhances efficiency, resilience, and sustainability.

Different biology, powerful together.

Bacillus species are endospore-forming (very durable) bacteria that colonize root zones quickly, even under stressful conditions. Their mobility and speed make them ideal for short greenhouse crop cycles. Once in place, and depending on the species, they produce a wide array of beneficial compounds — from plant hormones that stimulate growth, to peptides that support plant health.

Trichoderma species are filamentous fungi that establish more slowly, but persist with strength. They grow hyphal networks through growing media, decomposing organic matter, competing with pathogens, and stimulating root development.

These microbes operate differently, but complement one another beautifully in high-density, high-intensity greenhouse systems. Bacillus hits fast and hard; Trichoderma builds a deep and lasting foundation. And using them in rotation gives growers flexibility and choice. 

A common Trichoderma product is Trianum (T. harzianum T-22), though other species of Trichoderma like T. virens also turn up in some greenhouse products.  Trianum is widely used in hydroponics and inert media systems. From the bacterial side, Impello’s Tribus provides a ready-to-use solution: a high-density consortium of B. subtilis, B. amyloliquefaciens, and B. pumilus, all selected for strong root colonization, compatibility with standard fertilizers, and proven efficacy in commercial greenhouses.

What each of these species brings to the greenhouse bench.

Bacillus subtilis

Rapid colonizer, beneficial biofilm-former, and some strains can be potent producers of lipopeptides that suppress fungal disease. Supports early root development and strengthens plant defenses.

Bacillus amyloliquefaciens

Specialist in enzyme production — excellent at breaking down organic residues in media and releasing tied-up phosphorus. Promotes nutrient uptake and improves microbial structure in the rhizosphere.

Bacillus pumilus

Known for stress resilience. Some strains produce auxins that promote root elongation, and all survive well in substrates with variable moisture or salinity.

Trichoderma harzianum

Competitive and aggressive — it colonizes inert substrates like rockwool and coir, and suppresses root diseases common in greenhouses (e.g., Pythium, Rhizoctonia, Fusarium). Also helps in transplant recovery.

Trichoderma virens

A key biocontrol fungus in greenhouse systems, T. virens produces potent antibiotics and is especially effective in high-organic or humid environments.

Why they work so well together.

In greenhouses, where root zones are shallow, sterile or inert substrates are common, and disease pressure is high, combining or rotating these organisms offers robust, multi-layered protection. Bacillus quickly coats root surfaces and releases growth supporting compounds; Trichoderma reinforces roots from within and builds long-term resilience in the root zone.

• No biological incompatibility has been documented between Bacillus and Trichoderma — in fact, studies show synergistic effects in lettuce, tomato, and cucumber when used together.
  
  

• These species occupy different niches in the rhizosphere; in other words, they have slightly different preferences. Bacteria tend to stay closer to root hairs, while fungi penetrate deeper into the substrate.
  
  

• Multiple modes of action mean multiple ways of supporting plant growth, better suppression of undesirable organisms, and more consistent growth across variable greenhouse conditions.
  
  

While some growers tank mix these organisms together, many opt to apply them sequentially — not because of incompatibility, but because it’s often more economical and allows for targeted action at different crop stages.

The three yellowish-brown dots in the dish represent the Bacillus from Tribus and Continuµm, while the "hazy" material covering the entire dish is the Trichoderma. As you can see, the bacteria and fungi grow together without a zone of inhibition.

Real-life use in greenhouse crops

Here’s how these microbes show up in greenhouse practice:

• Lettuce and leafy greens: Bacillus applied via fertigation during germination to reduce damping off; Trichoderma drenched at transplant to protect roots and enhance uptake.
  
  

• Tomatoes and cucumbers: Bacillus used in drip line early in crop cycle; Trichoderma added mid-cycle to suppress Fusarium and support nutrient flow in fruiting phase.
  
  

• Cannabis and hemp: Trichoderma layered into organic potting mixes or coir at planting; Bacillus added weekly in low-volume fertigation.
  
  

• Ornamentals (e.g., geranium, poinsettia, hibiscus): Preventative Trichoderma drenches before peak disease windows, with Bacillus on rotation to stimulate rooting and bloom quality.
  
  

Best practices for greenhouse application

To get the most from Bacillus and Trichoderma in a greenhouse setting:

• Apply Bacillus early and often, especially during rooting, transplant, or vegetative growth phases.
  
  

• Use Trichoderma preventatively — it takes time to establish, but offers long-term protection when applied before disease strikes.
  
  

• Rotate if not mixing: For example, use Bacillus weekly, and Trichoderma every 2–3 weeks.
  
  

• Check substrate pH and EC, especially in rockwool or coir — extremes can impact colonization.
  

Collaboration as a growing strategy

Biological diversity isn’t just a philosophy — it’s a proven agronomic and horticultural strategy. In greenhouse systems, where precision and performance are critical, combining Bacillus and Trichoderma offers a science-backed path to healthier plants and more resilient crops.

These microbes aren’t at odds — they’re partners in the same system, each bringing their own strengths to the root zone. When used thoughtfully, they mirror the very ecosystems we’re trying to support: complex, collaborative, and full of life.

Ready to try this in your greenhouse? Start small. Try Tribus in your fertigation line and pair it with your favorite Trichoderma drench. Watch your plants respond — and let biology do the heavy lifting.