By Jeff Hickey

I always listen closely when more experienced growers speak. Since I came to growing cannabis much later in life than most I know, I benefit from the wisdom of their tales. Over the years, I have heard stories about bat guano from growers. Some swear by it to this day, while others insist it brought their gardens to the bane of our existence: MOLD.

On the positive side, bat guano has often been described as an excellent source of late season phosphorus for flowers, bringing vital micro and macro nutrients for the growing medium. 

But I was warned that bat guano is also full of active bacteria, and introducing that to your soil can lead to systemic rot in plants. That happened to one of my cultivars years ago, and we only discovered it on her harvest day.

We have bat houses on our property, and one this year became especially active. At the peak of summer, 30 bats were sleeping in this house and leaving their guano beneath in a catch tray.

After much consideration and consultation, I decided I wanted to try using the guano we are being given by the local bats, which happen to be the California Brown Bat. When I made this decision, I had plants already flowering and a few more about to flower, so I figured I would finally use guano as a late-season phosphorus boost.

When I researched this bat to find out more about them, I discovered the California Brown Bat is not known for phosphorus. It’s known for nitrogen, and that is because these bats eat insects, and not fruit, like the phosphorus-rich bats of the equator. Turns out, insects are a tremendous source of nitrogen in this particular guano, along with all the benefits of insect connective tissue and frass. California Brown Bat guano is a noteworthy soil builder and nitrogen replacer. If this guano was given an NPK, it would probably read something like 8-0-0, or 8-1-1. But here’s the best part: If dried properly before using, if all live bacteria is dead, you can use as much as you want because it won’t cause root burn. It is an important addition to the microbiology of my soil, and for goodness sake, it’s free!

So there I was, thinking I was going to boost the phosphorus, and instead, I could boost the nitrogen. I still wanted to try it this year, so I took a bunch to my drying room (without any cannabis drying) and set it on a rack in the middle of the room, turning on all the fans and air conditioning. The vents spewed guano odor for about three days, but it dissipated. After 10 days of drying, I took the tray outside during a very warm and sunny day and let it bake one more time under 88 degrees. After that, I put everything into a half-gallon mason jar for storage, and it’s ready to use.

I put 8 tablespoons (2 per gallon) into a four-gallon compost tea and aerated that brew for two days. Everything I read indicated that aerating for 48 hours would completely unlock the microbiology. I poured her into the soil of the four plants about to flower, or just starting to flower, and waited to see what happened. 

The four plants all grew, and two of them significantly. The most dramatic impact occurred on the largest cultivar we grew this year, the so-called West Marin Mystery, in bed 18. She was ready to flower, and then the guano hit her and she waited another two weeks before starting to flower with vigor. During the two weeks after the guano dose, this plant grew 14 inches. She had been slowing down prior to the burst. There could only be one explanation, the guano.

She grew and Bee trained her aggressively, stretching her into neighboring beds and across the middle aisle. They tied her to tomato cages in other beds for anchoring the trains. With the nitrogen boost, and the stress of the trains, she gladly grew in every direction.

I will begin using guano next season in aerated compost teas after completing solarization for my beds. I’ll use it again after cutting down the favas in preparation for planting, and I’ll use it when next year’s crop is brought out to the beds. I can’t wait to see what happens next year.

But as for the grow this year, some fascinating things took place. It was my first year with auto flowers, and the results were generally positive, with one large exception. I grew eight Blueberry Kush auto flowers, six in beds and two in cloth pots. Five of the eight plants were what I expected, small, with several fat, potent-looking flowers. 

But three of the plants grew over four feet tall, with many fat flowers. Cloth pots are fine, but even a five gallon cloth pot cannot yield the same size plant as I can produce in one of our beds. The largest, pictured below, produced over 200 grams, just a little shy of half a pound.

From the eight autoflowers, that took no particular skill on our part to grow, just the same food we give our plants, and all our foliar sprays, we yielded a total of 597 grams, or 1.31 pounds. Auto flowers are ridiculously easy to grow, but they are not meant to be ignored. I was given great advice by one of my fellow faculty at OU, Eviane Ita. She told me to love them exactly like I love my big plants, so we did, and it showed. Highly recommended for anyone to grow. Auto flowers could be a game changer for home growers.

That said, however, we had one unexpected disappointment that I placed squarely on the shoulders of the auto flowers, though no scientific proof exists for what I’m about to claim. That being, I believe the auto flowers influenced three of the four feminized CBD seeds I started to flower early, and they could not be persuaded back into vegetative growth. It’s the first time I’ve failed to turn early flowers back to veg, and I’m pretty convinced it was the auto flowers influencing the feminized seeds. Something about the pheromones in the air. We know that feminized seeds are highly sensitive. They don’t like being heavily stressed, and something about being planted in proximity to flowering plants was too much for them to withstand along with being transplanted outdoors. The auto flowers did not influence my regular seed plants. But I grew four high CBD plants this year, all feminized, and only one grew to her full harvest. The three, including a second Ringo’s Gift, a Harlequin and a Sour Tsunami grew quickly and potently. The plants were small, but they were powerful looking flowers. For my upcoming hip surgery, these plants will play a key role in weaning me from opioids during my recovery. So the plants were not a success in terms of quantity, but the high quality medicine they produced will still play a key role. And next year, one of my primary goals will be to grow more CBD plants to bolster our dispensary. I won’t grow autoflowers next year.

But of everything that happened this year, we also experienced the single largest game changer in all our years of growing. I hate that I’m going to sound like an infomercial here, but I cannot exaggerate the efficacy of the following product: Stargus by ProFarm, formerly Marrone Bio Innovations. For the record, I was not financially compensated by ProFarm to write this blog.

Stargus is a foliar spray application. We mixed two tablespoons per gallon of water. It is applied once a week only, directly on the flowers and stems for the first four weeks of flowering. After that, you can continue spraying once a week, but as the flowers close and access to the inside is denied, there’s not much more to be gained by spraying. There is no harm, however, in spraying anyway. Another bonus is that you can spray this anytime of the day. Direct sunlight does not cause problems, and it also interacts well with other foliar sprays you may be using, like BT, or Regalia, Grandevo and Venerate, for example. Stargus has a shelf life of 18 months for maximum effectiveness. Best stored indoors. 

Our farm is in a rain zone in Northern California, despite the drought. We also have variable coastal humidity throughout the growing season. Botrytis is our enemy and our constant unwanted companion as summer advances into autumn outdoors. It can be a plague, and if left unchecked by the unwary or new grower, it can cause your crop to explode with mold. Historically, we have fought this with observational diligence, scissors, tweezers, organic honey and strategic dabs of isopropyl to kill mold. We have learned to harvest around mold, extracting as much medicine as we can from rot infested plants. We have also come to understand the value of harvesting early, in order to save the medicine before it gets a chance to mold.

In addition, as some of you who read my work know, we use a lot less water than most other growers, in part to cut down on potential mold. But we cannot fight the elements outdoors. Diligence alone will not stop pathogens from spreading once they take hold.

Until this year. This year, we saw mold, though significantly less than we’ve ever seen, but the reduced quantity (though noteworthy and wonderful) wasn’t the most amazing part. It was the quality of the mold, and how it was consistently not allowed to spread through flowers, or even blemish part of a stalk. Time and again, we observed what we called “The Stargus Effect.” This was where mold existed in a spot, but was only advancing very slowly around it. Where mold was touching either flower or stem, there were no signs of spreading to those surfaces. It appeared to us as if a force field of sorts existed, preventing mold from entering its zone. It reminded me of the way the odor of lavender repels deer from our garden fence.

In fact, what Stargus is doing is colonizing and exuding lipopeptides to suppress botrytis growth. This is what gives it the impression of the force field. Here is an example from the laboratory, sent to me from ProFarm:

In this slide photo, you see a piece of peat moss at the top and bottom. Both have been infected with botrytis. The top piece got Stargus, and you can see the force field it puts out to inhibit the spread of mold from the unsprayed piece at the bottom, where mold is rampant.

We observed this on our plants repeatedly, throughout the summer. Every cultivar showed the Stargus effect. This is important, because this summer, from the second week of June to the middle of October, when harvest ended, our average humidity in my garden was over 70%. In the early years, this would have been unsustainable for us to have a six month cannabis grow. Our grow would have exploded with pathogenic activity. As it turned out, it wasn’t a problem at all this year. We had less mold, but we also had dramatically less mold spread. 

See the mold in the above photo. But note that it is growing out and away from the flower. It looks almost mossy and wizen, which is something else we observed about much of the mold we removed. It could be removed without cutting the plant. For example, the mold above was removed with tweezers. 

Now look after the mold is removed. There isn’t a trace anywhere on the flower or stem. In fact, the mold tried to grow away from the plant. No cuts were made requiring honey for treatment, and no alcohol was applied to kill mold, so no trichomes were sacrificed. 

This is typical of what we saw through most of the summer, though it must be emphasized that the overall incidents of mold were also cut by well over 50% in our estimation. Even in this oppressive humidity, the plants resisted mold. 

Our largest plant, the West Marin Mystery, was also the last plant to harvest. She was due to come down around October 19, but early in October, we began to see mold pop up on her in a way that was different than any other plant in the beds, and more typical of mold we’d seen in the past during this time of year. This mold looked juicier. So we wondered if the Stargus worked best earlier in the summer, but wilted when harvest went late into the fall.

That was not the case.

We began to suspect, only in that one plant, that we might have a systemic issue, something on the inside. The mold that was popping up was not so airy and wizened as pictured above. It was the more traditional, and very aggressive botrytis. Though it must be emphatically stated that even the most aggressive mold was being limited by the Stargus. Separate molds on the same flower were not joining forces. They were remaining separate. We found different molding piles of worm scat on the same flower, in close proximity, that were not joining. We’d never seen that before. There’s only one explanation for this stubborn separation and it’s Stargus.

We eventually made the correct decision to take her down a week early, when the average low humidity remained close to 82% for consecutive days.  Humidity that high is not defensible. Our priority always is to save the medicine.

After processing the plant, washing her and setting her up to dry, we split the main stem to look inside and sure enough, a tiny crack had opened on the innermost train, something we could not see without taking her down. She was too big to inspect deep inside. So into this tiny hole crawled some insects, probably spider mites, and they climbed through the cavity, leaving scat wherever they went. This scat was molding, and it didn’t have any Stargus to inhibit it on the inside. We were fortunate to take that large plant down when we did. A few days more, and we would have lost large chunks of her to systemic mold. As it was, this is what that large, beautiful plant looked like after taking her down, and just before we started processing her:

The 2022 grow was unique. It had the fewest insect and/or pathogenic problems I’ve ever faced in a full season of growing. Stargus was a revelation, and should be a game changer for all growers, outdoor and indoor. We now have a tool to fight mold. The entire IPM program of Grandevo, Venerate, and Regalia for powdery mildew, were completely effective this year. All of these products are made by ProFarm, and I learned that Grandevo, Venerate and Stargus are most effective when used exactly as directed. On the other hand, Regalia may be safely used every day, if necessary, to combat powdery mildew. During periods of massive, sustained humidity, one day a week is not enough spraying for Regalia.This year, three mornings a week did the trick. If conditions are not so extreme, once a week would probably work fine. But doing it more often is safe, and remember, we wash all of it off at harvest.

My own discipline as a grower was also acute, helped in no small part by having my right hip replaced two weeks prior to starting seeds. It’s amazing how much work you can do with one good leg. Being half liberated from pain brought a resurgence to my discipline, and joy as a grower. Every foliar spray this year was pre-dawn. It was the first year I never snuck in a spray on a cloudy day. I sprayed five days a week. With humidity so consistently high, I had to spray, and they worked. Over a period of years where I have consistently treated my soil, I’m finally seeing the fruits of my labor. Less bad insects, and more good insects. This year, my plants were covered in predatory flies. They chose our plants as their summer homes and nurseries. Honestly, the amount of insect copulation that occurred in front of us, sometimes while we pruned leaves around them, was pretty comical. If you didn’t know these were the good kind of flies, you’d be tempted to shoo them away. But the flies rested on our plants, making babies, and hunting for any bad insects that dared to land nearby. We had the most insect free plants we’ve ever grown.

Dragonflies had their annual feast after the first rains of autumn awakened termites who live in the ground. I watched the termites fly, and the dragonflies pounced, sending termite wings fluttering to the earth and the welcome, sticky fingers of my flowers. Thank goodness we wash our plants!

I am looking forward to the 2023 grow, to see if we can replicate the IPM success we had this year. I’ve been told by growers that some years are like that, while others can be a seemingly endless stream of difficulties. I’ve had those years, too. But this year felt different. I cannot honestly say the difference is entirely a product of work, or that it’s also a manifestation of a changing climate. It’s probably a bit of both. When I first began to grow, we had all manner of pest and pathogen issues. We lost 40% of our second year crop to mold caused by moth worm scat.

This year, the greatest stress we faced were three feminized plants that insisted on flowering early. We saw barely any bad insects. I killed perhaps six Western Cucumber Beetles with my fingers, an all time low. I barely saw this pest, and in previous years, I’ve had to tent my plants against Western Cucumber Beetle swarms. Found out that Grandevo is a Western Cucumber Beetle deterrent. For the growers where this insect preys and swarms, there are now things far gentler on the environment and all living things, than Pyrethrin. 

For the summer, with humidity consistently over 70% and 80%, we cut off perhaps two dozen leaves with powdery mildew. From the second week of June to the first week of October, I sprayed Regalia three days a week, every week. With that level of humidity, I had to take a proactive approach to both pathogens and pests, and it all worked better than we’ve ever seen it work before. We only had one plant that showed systemic mold issues beginning and as described above, we harvested her before it became a serious problem.

I want to make a note here about harvesting early. Some growers view this as almost sacrilege and will sacrifice parts of their plants in order to achieve the perfect harvest date. I used to be one of those growers.

I will not fall prey to this ignorance again. Harvesting early is not a detriment to the medicine you’ve grown. In fact, some claim that the much desired potency actually peaks a week or so before the perfect harvest date. My only evidence to support this is last year’s harvest, when I took down all but one of my plants up to nine days early, to combat the rampant mold problem. Even with those early harvests, my test scores last year were the most potent to date in both THC and terpene percentage. I had one plant show 3.2% terpenes, which is extraordinarily high for an outdoor grow. All that said, the most potent plant I grew last year, a 27.40 THC potency in an AK47, was the only plant that went to her full harvest date. The bottom line on this is to not be afraid of harvesting early. I am now a believer in early harvest to save the medicine, as opposed to fighting through mold to salvage medicine on a rotting plant.

Our 2022 grow produced 12.55 pounds, 5,697 grams, 200 ounces, and it all went into exactly 72 mason jars. It would have been a 16-17 pound harvest, except for the early flowering feminized plants. Live and learn. Next time I grow autoflowers, it will be over the winter and they’ll be harvested and dried long before I start my spring seeds. Start to finish, the 2022 grow took six months and two days.

It was an especially noteworthy grow for me by virtue of the fact that it was bookended by two hip replacement surgeries. My right hip was replaced two weeks before I started seeds in April,, and the left hip is being replaced 13 days after harvest is finished. All I can say about that is should a doctor ever tell you that you need new hips, go bionic. Having the hips of a 25 year old is awesome when you’re 65.

Before I conclude, I wanted to offer a few words of thanks to our child, Bee, who trains our plants, trims at harvest, and who provides fresh eyes throughout the growing season when we’re searching for pathogenic problems. In addition to the joy of working with our child, I can honestly say that our grows would not be as successful without them. They have a gift in the garden, and it is my distinct pleasure to be the grateful beneficiary of their vast skills and unique vision. Thank you, sweet.

Our 2022 grow had a positive, serendipitous quality to it. We are curious if we can replicate the IPM and pathogenic results next year. Our 2023 garden is going to be more diverse than this year. More food will return, tomatoes, sweet peppers and much more. We’ll probably grow no more than ten cannabis plants. But everything I grow next year is going to have a full protocol of nitrogen rich bat guano and I can’t wait to see what impact that has on the grow and my soil. 

There will be an emphasis next year on two things: CBG and CBD. I hope to be growing strains known for being high in CBG and we’ll be harvesting them weeks early, in order to maximize the amount of pure CBG we can extract. I need to know more about it and work it into our sleep and pain medicines. More CBD plants will be grown without the interference of autoflowers. I might be growing my first ever hemp plant(s), that are specifically high in CBG.

And I’ll have two new hips. My lovely wife of 40 years has perhaps the most accurate perspective on this. She’s thrilled for me, of course, because she knows how long I’ve been in pain. And I’m sad that I can have surgery to fix my pain, when she cannot. But she’s known me longer than anyone and is coming to grips with the implications.

She said, “When you get that second hip, you’re liable to become obnoxious.”

Love that girl.  

See you in Hort Lab, I hope.

Jeff Hickey is an avid grower and Oaksterdam Home Grow faculty member. Ask him anything during Oaksterdam University’s weekly Hort Labs, Fridays at 10 a.m. PT. Hort Labs are open to alumni and asynchronous students are invited. Check your inbox for your Zoom link to enter the video call. Read more of his blogs here.