Trichoderma harzianum T-22 for Root Rot Prevention
Beneficial root fungus · Trichoderma harzianum T-22
4.8 · 8 reviewsTrichoderma harzianum T-22 is a beneficial root fungus, shipped as a wettable powder of dormant spores and sized by the gallons of drench it makes. Watered in at potting, propagation or deflasking, it colonizes the roots ahead of root-rot fungi such as Pythium, Rhizoctonia and Fusarium. It is a preventive: it may not catch up on a plant that is already rotting, and a broad-spectrum fungicide will kill it.
- Good to know
- Mostly invisible. It goes in as dormant spores with a watering and works down at the roots. Nothing changes on the leaves, and that's normal. What to expect
When to choose something else
Not for powdery mildew & leaf spot, bacterial rot, insects, fungus gnats.
Shipping details
Shipping
| Est. ships | Est. arrives | |
|---|---|---|
| Standard | ||
| Overnight |
Raising a fresh batch for you? Add up to 7 days to both dates.
Estimates. Overnight speeds up the trip, not the packing: its one day on the truck starts once it ships.
- Monday to Thursday only. Nobody spends the weekend in a warehouse.
- Check your address at checkout. Bugs are brilliant at finding aphids and hopeless at finding a new front door.
Ordering with friends? Get group pricing
Everyone picks their own. It ships to you in one box.
Buying for a greenhouse, farm or shop? Ask about wholesale
Right for you?
Your pest, your growing space, how many you need
Or choose instead
When one of these fits your situation better than trichoderma harzianum.
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Choose this instead
Sf Nematodes
If the problem is in the soil and moving.
from $15
Conditions for releasing grams
The conditions, one line each.
Temperature50–90°F soil
Establishes well from about 60°F up, which suits most tropicals and indoor grows; at 50°F it is slow to take hold. That wide bar is the strain's whole selling point.
HumidityMoist medium, pH 5.5–7.0
Spores need moisture to germinate, so drench a medium that is already moist rather than bone dry — but not waterlogged. Keep it out of direct intense light while it waters in: UV degrades spore viability.
Coverage1 gram per gallon
One gram per gallon of finished drench for established plants. Half a gram for tissue culture and cuttings; a gram and a half for mother plants and high-stress areas.
RefrigerateOnly for long storage
Sealed, cool, dry and dark is fine for six months. Beyond that, refrigerate at 35–45°F and the spores hold for up to eighteen. Never freeze, keep above 32°F, and keep the pouch sealed — humidity in the bag activates the spores where you do not want them.
Releasing
What to do, and what you'll see
What to expect
- Mostly invisible. It goes in as dormant spores with a watering and works down at the roots. Nothing changes on the leaves, and that's normal.
- A white fuzz is usually good news. Sometimes a soft white fuzz shows on the soil surface after a drench. That's usually the colony itself settling in.
- Judge it by the roots. Cuttings that strike instead of damping off, and transplants that push new roots instead of sulking.
How to release grams
Reviews
What growers say
What people say
4.8 out of 5, from 8 reviews.
Good product, fast delivery! Thank you!
Hard to measure out how much you need, but otherwise, ive really enjoied everything ive purchased from this shop.
After reading many articles, I decided to order Trichoderma. I used it according to the instructions, and so far my plants are in very good condition. I reduced fertilizing because after applying it, the plants do not show any nutrient deficiencies. I think it was a good decision because at this time last year my plants were already getting sick. The ordering process itself was trouble-free, and I waited about a week for the delivery, but it was worth it.
This is magical. I love it
Ordering and delivery were flawless. Instructions for use and storage were good and helpful
It’sgood
It's my first time using Trichoderma solution as a bio-fungal agent to prevent damping off. This stuff is great. I've already had success using it as a pre-soak and soil drench to germinate adeniums, aloes, and boswellia, and I've also drenched the soil of my other native plant starts. I've had zero issues with mold growth or damping off so far.
I love it! Good product! Thank you!
Does this help with black rot on grape vines
Hi!
Unfortunately, no. That’s more of a foliar disease.
Good product, fast delivery! Thank you!
Hard to measure out how much you need, but otherwise, ive really enjoied everything ive purchased from this shop.
After reading many articles, I decided to order Trichoderma. I used it according to the instructions, and so far my plants are in very good condition. I reduced fertilizing because after applying it, the plants do not show any nutrient deficiencies. I think it was a good decision because at this time last year my plants were already getting sick. The ordering process itself was trouble-free, and I waited about a week for the delivery, but it was worth it.
This is magical. I love it
Ordering and delivery were flawless. Instructions for use and storage were good and helpful
It’sgood
It's my first time using Trichoderma solution as a bio-fungal agent to prevent damping off. This stuff is great. I've already had success using it as a pre-soak and soil drench to germinate adeniums, aloes, and boswellia, and I've also drenched the soil of my other native plant starts. I've had zero issues with mold growth or damping off so far.
I love it! Good product! Thank you!
Does this help with black rot on grape vines
Hi!
Unfortunately, no. That’s more of a foliar disease.
Pairs well with
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Special Blend Slow-Release Prevention Sachets
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More to know
Ways to buy, questions and reading
Ways to buy
Once, on a schedule, with friends, or mixed with other predators.
- One time
- A single pouch, this once. Free shipping on orders of $30 or more, $15 under that.
- On a schedule
- 10% off your first box, 15% off every box after. Skip, move, pause or cancel from your account.
- Group order
- Friends each pick what they want, and it ships to you in one box.
- Mix and match
- Buy several predators together and they get cheaper.
For the curious
Everything else we know about them. Tap a topic to open it.
Is this your problem?
While predatory mites guard the leaves, T-22 guards the root zone. It is a biological fungicide and a root enhancer in the same jar.
Root and crown rot announce themselves late and from the wrong end: wilting that watering does not fix, a stem going soft at the soil line, a cutting that damps off overnight, a plant that simply stops. By the time the foliage tells you, the roots have been losing for a while.
T-22 works against the organisms behind that — Pythium, Rhizoctonia, Fusarium, Thielaviopsis and Cylindrocladium. What it does not touch is anything above the soil line: foliar disease like powdery mildew and leaf spot, bacterial rot, insects, or fungus gnats.
Then: is T-22 the right answer to it?
Choose this if
Choose it for the moments when the root zone is bare and something is going to colonize it — potting and repotting, a cutting striking, a tissue-culture plantlet coming out of a sterile flask with no root biology at all, a mother plant you would rather not gamble on, or any soilless medium that starts as a blank slate. It works by taking the territory first: colonizing the root surface ahead of the pathogens, using the space and nutrients they would have used, parasitizing the pathogenic fungi directly, and switching on the plant's own defense response. Applying it is a watering. Nothing to spray, no residue and no re-entry wait — you stir a gram into a gallon of dechlorinated water and pour it in. It reaches the whole root ball rather than the surface, it goes on working for the life of the root system rather than the few days a drench lasts, and it is compatible with mycorrhizae, beneficial nematodes, predatory mites, springtails and many insecticides.
Choose something else if
It is preventive, and that is the honest framing: T-22 takes territory before a pathogen does, and on a plant that is already rotting it may not catch up. It is also the wrong product for anything above the soil line — powdery mildew, leaf spot and bacterial rot are all outside what it does, and so are insects and fungus gnats. And it cannot be run alongside a systemic or broad-spectrum fungicide, which will kill the colony outright.
What it kills, and what it won't
This particular strain is the reason the list is that long. T-22 was bred to colonize across a wider band of soils and temperatures than most biological fungicides manage — active from 50 to 90°F and across pH 5.5 to 7.0, which covers soil, coco coir, perlite and rockwool alike.
How it works
What it does to the pathogen, what it does for the plant, and what that leaves you looking at.
It takes the root surface first
Colonization, not combat. T-22 occupies the root surface and the exudates a pathogen would have used, so there is nothing left to establish on. That is why timing beats dose here: the product is most valuable on a root system that has not been colonized by anything yet.
Then it attacks, and it recruits
Where a pathogenic fungus is already present, T-22 parasitizes it directly. And it induces systemic resistance in the plant — the plant's own defenses come up, which is a second line you did not have to buy.
It grows with the roots
A chemical drench lasts days. A colony lasts as long as the root system does, spreading outward as the roots spread, which is why the reapplication trigger is repotting rather than the calendar.
Dechlorinate the water. Chlorine and chloramine reduce spore viability, so treat tap water first — and use the mixed slurry the same day, because spores do not hold in solution.
About Trichoderma T-22
A living shield around the roots that grows outward as the root system grows. Preventive by nature, and best value at the moment of potting, propagation or deflasking.
New to biologicals?
Five things that catch almost everyone the first time.
What arrives
A sealed pouch of wettable powder — dormant, viable spores, sold by weight and sized by the gallons of finished drench it makes.
Nothing about the pouch changes on the way to you, which makes this the most forgiving thing we ship. Spores are shelf-stable at room temperature in transit; the only real enemies are sustained heat over 100°F and a bag left open to humidity.
Pre-mix before you dilute. Stir your dose into one cup of room-temperature water and whisk for thirty seconds until it is smooth, then pour that slurry into the full volume. Dry powder tipped straight into a tank floats on top and never reaches the roots.
When it ships, and when it lands
Shipping
We ship when they're ready to travel. Live orders go out Monday to Thursday. If a colony needs a beat to peak, or we're propagating a fresh batch, yours might hold up to a week. All mites and insects ship 2-day or Overnight depending on what's best for them.
When it lands
Store it sealed, cool, dry and dark until you need it. When you drench: measure the dose, pre-mix it into a cup of water, dilute into dechlorinated water, and pour at the base until the root ball is saturated. If you are working down a bench, stir the bucket every few minutes — the spores are heavy and settle. Apply out of direct intense light, in the early morning or evening or under grow lights, and use the slurry the same day.
About how long it stays viable
Nothing in this pouch is alive in the way the rest of the catalog is. It keeps.
Unlike everything else we sell, nothing in this pouch is awake. T-22 ships as dormant spores, which is why it travels better than any live insect we handle.
Short exposure to ordinary transit temperatures will not kill it. What will, over time, is heat above 100°F, freezing below 32°F, or humidity getting into an open bag and waking the spores inside it.
Sealed, cool, dry and dark, it holds for about six months. Refrigerated at 35–45°F, up to eighteen.
If something goes wrong
A pouch that arrives split, damp, or after a week in a 110°F mailbox is worth telling us about, and so is a drench that visibly fails to do its job on a batch of cuttings.
There is no tap test for a fungus. The honest check is the outcome, and that takes a few weeks rather than twenty minutes.
Tell us anyway. A split or soaked pouch is something we can see, and it is how we tell a bad batch from a bad courier day.
Why we will not ask for a photo
Mites, nematodes, eggs — and spores, which is what this is. A pouch of powder can't be judged by eye, so there is nothing for you to check or photograph.
Email info@fgmnnursery.com and we take you through the diagnostic instead — how the pouch was stored, what water you mixed with, how long the slurry sat, and what else went on the plant in the same two weeks.
What we will ask about is storage and mixing, because that is where viability is usually lost: chlorinated water, a slurry left overnight, a drench into bone-dry medium, or a fungicide applied in the same two weeks.
Seventy-two hours from delivery, either way, with your order number. Replacement or store credit, your pick.
Questions about grams
Will I have bugs flying around my house?
No. They stay on the plants, where their food is.
Is T-22 a fertilizer?
No, it is a beneficial fungus. However, research on this strain shows it can "solubilize" some nutrients—freeing minerals such as phosphate, iron and zinc that are otherwise locked up, so the plant can take them up.
Can I use T-22 if I already have Root Rot?
T-22 is most effective as a preventative. If your plants are already dying from advanced root rot, T-22 may struggle to catch up. For best results, apply to healthy plants or at the very first sign of stress.
How often should I apply it?
A single application at planting can last for months, but for high-intensity indoor grows, we recommend a "booster" drench every 4–6 weeks to ensure the root zone remains fully colonized.
Will it harm my Beneficial Nematodes or Soil Mites?
Not at all. Trichoderma is a fungus that targets other fungi; it does not harm beneficial insects or microscopic worms. In fact, they often work together to create a healthier soil ecosystem.
I see white fuzz on my soil after using T-22. Is that bad?
Usually, no! That is often the Trichoderma colony growing on the soil surface. It isn't harming your plant.
How does T-22 help with acclimating Tissue Culture (TC) plantlets?
Tissue Culture plantlets are raised in a sterile, 100% humidity environment and lack the "microbial memory" needed to survive in the real world. When you move them into soil or coco, they are entering a biological vacuum. T-22 acts as an early "bodyguard," colonizing the roots before harmful pathogens can, which is why deflasking is the best moment to use it.
Can I use T-22 with a fungicide?
Not alongside a broad-spectrum or systemic fungicide: it can't tell T-22 from a pathogen and will kill the colony. The registered T-22 label says not to tank-mix it with benomyl, imazalil, propiconazole, tebuconazole or triflumizole, or to apply it right before them.
How long to wait after a fungicide depends on its active ingredient and how long it stays active in the soil, so check that product's label. There is no universal waiting period.
How much T-22 do I need?
Size it by the gallons of finished drench you will mix, not by plant count. Each size is named for the gallons it makes at the standard rate:
- Measure: how many gallons it takes to saturate every root ball you are treating this time.
- Established plants: 1 gram per gallon, so pick the size that matches your gallons (the 5 Gallons pouch makes 5 gallons).
- Tissue culture and cuttings: half a gram per gallon, so a pouch goes twice as far.
- Mother plants and high-stress areas: a gram and a half per gallon, so a pouch makes two-thirds as much.
There is no pest count here, so there's no sizing up or down for pressure. One pouch is one batch of drench; keep any extra sealed in the fridge. Drench again after repotting or a heavy media change, and every four to six weeks in a high-intensity indoor grow.
Keep reading
Field Notes from the FGMN Nursery team.
The Fungus That Fights for Your Roots
T22 is not a pesticide. It's a fungus that colonises plant roots, hunts and eats soil pathogens, produces…
Finding the Roots Worth Saving
Start with what is still firm and alive. A root-inspection and salvage guide before another bottle goes into…
Wilting in Wet Soil?
The pot is wet. The leaves are limp. Before you reach for the watering can again, here is…
Sources
Published guidance from university extension services. The release tips on this page also draw on what we see shipping these every week.