Trichoderma Harzianum, The Useful Fungicidal Fungi.

 Trichoderma harzianum soil fungi

It’s a dog-eat-dog world or rather a fungi-outcompete-and-parasite-and-ultimately-obliterate-fungi world out there, in the soil of our gardens and farms. Even though it may look like a peaceful late summer afternoon or a quiet spring morning, among the roots of the plants, on their leaves, on their fruits and on their flowers, fierce battles are fought between millions of little microorganisms in their struggle for life. Some of them are our allies (the probiotic bacteria, or the mycorrhizal fungi), and some of them are against our human interest and so we call them plagues.

Trichoderma harzianum,in particular, is a species of fungus counted among the surest allies of the gardener and the farmer. Put simply, it is a species of fungi that has evolved to obtain its nutrition from a symbiotic association with plants, through which both the fungus and the host plant benefit. It colonizes the roots of crops, garden flowers, bushes, fruit trees and indoor plants, and benefits the plants in three main ways:

  1. Trichoderma harzianum helps plants reach deeper into the soil and process nutrients better, by acting as an extension of the plant’s roots, trichoderma t22 and as a regulator that improves consumption and use of nutrients from the plant’s surroundings. It is the closest thing in the vegetal world to a bionic implant, adapted through evolution to respond perfectly to the plant’s needs.


  1. It serves as a protective barrier between the climatic conditions and the plant, both by the prolongation of their roots deeper underground (where conditions tend to remain more or less the same), and by activating their genetic response to environmental challenges. Studies have shown that plants inoculated with Trichoderma harzianum are far more resistant to adverse conditions of cold, heat and even salinity, reducing the impact of cold snaps, heatwaves and changing soil conditions.


  1. Finally, it also kills and outcompetes dangerous species of fungi. Trichoderma harzianum has evolved to benefit from the health of the plants that host it, by feeding from their excess sugar production, so it will go to any lengths to prevent the death of the plant that serves as its home.

This variety of fungi is, in fact, so good at this last role that Trichoderma harzianum (or some other species of Trichodermaspp.) forms the basis for around 60% of all organic fungicides in the market. If you’ve got a fungal infection or the menace of one, chances are that the organic fungicide you bought includes Trichoderma harzianum as the active agent. As it develops, trichoderma spores, this species will kill dangerous fungi by outcompeting them and pushing them out of your soil, by serving as ‘plant vaccines and stimulating resistance in your plants for when the real enemy comes along, and by actively producing antifungal substances (harzianic acid, azaphilones and harzianopyridone, to name a few) destined to kill competing, dangerous fungi.

Using and introducing Trichoderma harzianum in your garden or farm is, in short, something along the lines of fighting fire with fire, with the added value that the ‘fire’ you’re using will actually add fertility to your soil and vitality to your plants. In contrast to using inorganic fungicides (which are a bit like fighting fire with an outright nuclear blast), the introduction of these fungi to your garden will not deplete it of microbial life, nor turn your soil into a less-rich ecosystem,but will on the contrary help introduce a balance in the type of life that your soil houses.

A garden or a farm are, after all, ecosystems that we human beings made and that we care for, but that ultimately belong to nature. Isn’t it wonderful to know that it gives us, as well, the product of millions of years of evolution as a tool to keep them flourishing and healthy?

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