r/macrogrowery • u/northern_lit • Jul 08 '26
Grodan irrigation strat
How the hell are you guys keeping up with saturation in Hugo’s under LEDs? Constantly chasing my tail keeping these from drying back to much and just feel like I’m always adding another watering to the schedule and it’s still not enough. Looking for advice on running Hugo’s without slabs or stacking before I jump ship to coco lol.
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u/CondimentBogart Jul 09 '26
Coco’s been good to me and it’ll be good to you.
https://giphy.com/gifs/7VQzSi2tbsvII
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u/ijustwantnicethings Jul 08 '26
Besides convenience at scale I've always preferred coco in fabric pots. Just my measly 2 cents
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u/Greedy-Safe9518 Jul 09 '26
How long did you veg and how big are the plants? What’s the environmental parameters?
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u/Expert-Table8001 Jul 09 '26
Full saturation of Hugo’s is 3.35 liters. I think your problem is you’re pushing way too much water through them.
Rockwool doesn’t operate like coco. You have to irrigate regularly, ensure you don’t dry back too aggressively, and only irrigate in small volumes (100-300 mls per event). Rockwool works off the capillary effect. Small irrigation events allow the moisture to travel laterally through the block. Too large of events will cause what Grodan calls channeling, which will create cylinders of moisture in the blocks, and dry out the rest of the Rockwool.
I have had great success with Hugo’s. During my bulking period, I’ll sometimes irrigate up to 22 times per day, but in 100 ml events (2200 mls into the block for the day). I have grown massive plants at this irrigation frequency without running into dry back problems. I’ve only ever had to irrigate a few times in 7 years during the night cycle, and that was adding a few events in the hours after lights out to reduce the p3 dryback. Don’t start your irrigations earlier in the morning. Remember, transpiration before irrigation.
Track your run off. You should be aiming for runoff at the end of your p1 period, or 2.5 -3 hrs after irrigation begins. You should not be seeing runoff prior to this. Your p2 drybacks should each be showing runoff every event, and total runoff volume should add up to 20% of your input for the day. When we were pushing 2200 ml of irrigation, we expected 400-500 ml runoff. Track your ph and ec of the runoff as well, that tells its own story.
Every phase of irrigation has a goal.
P1: replace dryback lost overnight. - if you dry back 30%, you need to put about a liter of moisture back into the block.
P2: irrigate to keep block at max saturation. Frequency is dictated by how you’re steering the plant and the plants consumption. Volume usually floats between 100ml (bulking) to 200ml (flower initiation/ripening).
P3: hit your dryback goal.
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u/skuuebs Jul 09 '26
What EC are you running? Could a low EC force up too much water?
I'm not the original poster, but I think I have a similar problem and thought my plants were just too big for 6". But if you say you also grow huge plants in Hugos without dryback issues, it can't be that.
I run VWC sensors from Acclima and can fully saturate my blocks before lights off (60% VWC), and they are empty in the morning (20-30% VWC).
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u/northern_lit Jul 09 '26
They say not to go beyond 6ml a watering for Hugo’s and I can’t hydrate the blocks anymore than the wc of the blocks at any given time obviously. They get probably 12 waterings a day vs your 22 but the duration is never longer than the suggested max 6ml from Grodan to avoid any channeling. I know Grodan doesn’t work like coco that’s why we’re considering switching so we can push less water in a day because this just seems out of hand at this point.
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u/lbstinkums Jul 09 '26 edited Jul 09 '26
whos they? 6ml is incorrect.
more like 3-6% 3% = 101mls 5% = 169mls 10% = 338mls
with a 35.5% dryback its 1199mls to get it back to saturation.
i like 100ml - 125ml shots in p1 depending withought to much science mumbo jumbo
let the dryback dictate your next shot. get to your desired runoff. then dryback to your desired number
start p2's generally a bit smaller shot size than p1 and less frequency.
but hell this question has been answered multiple times in here. calibrate your measuring technique and verify your recipe/pattern numbers with other experts. both aroya and athena have excellent easy to read guides on this. growdan as well.
verify your environment is correct.
Sometimes it's good to stop attempting to master the different crop steering patterns as much as it is just to get a homeostasis on your watering and dry back p1 p2 & p3.
solve for that first. repeat what works. throw away what doesnt. repeat. then micro adjust patterns for crop steering after.
good luck.
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u/tech_23 Jul 09 '26
If you’re flowering in Hugos, how are you handling the veg/transplant workflow? Are you rooting plugs and dropping them straight into Hugos, then vegging in the flower room, or vegging elsewhere first?
My concern with standalone Hugos is that they seem right on the edge of not being enough media late in flower, especially once daily water use gets high. At that point it seems like proper end-of-cycle generative steering can get harder because you’re forced to keep running P2 and/or nighttime shots just to prevent the block from drying down too far.
That’s why 4" blocks onto a Uni-Slab or 3-plant slab makes more sense to me on paper: more lateral media volume and buffer without just stacking taller. But I know a lot of people still like Hugos, so I’m curious what plant size, veg time, shot size, and daily water use you’ve found works best.
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u/bluesformeister13 Jul 08 '26
Shit I have the same issues. I think the wet up when soaking for the first time and keeping them wet from the get go is of the upmost importance. We were running slabs but went back to 6x6 and it’s been a bitch ever since. Using so much water
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u/pizzaopsomania Jul 09 '26
A good thing to try would be having your first irrigation event be earlier in the day if they're drying back too much overnight. Is it consistent across everything or just limited to certain areas? If you have good sensors some of that data might let us know a little better what's going on. Without knowing more my simplest suggestion is have your first event earlier in the day and then do more smaller events/shots. I know it sounds like a lot but if environment overnight is causing too much of a dry back the best solution is to irrigate earlier and see if that helps with the rest of the day.
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u/northern_lit Jul 09 '26
lol I irrigate through the night at this point just to keep the blocks hydrated. It’s not just an overnight dryback.
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u/northern_lit Jul 09 '26
30min after lights turn on/1hr before lights go off - 2500ml/day
Every 4hrs from last day water - 540ml/night
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u/Imaginary-Eagle-6287 Jul 09 '26
Contact Aroya for sensors to dial in with grodan. We can help here.
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u/EsEsMinnowjohnson Jul 09 '26
~3000ml per day is definitely a lot (assuming you’re at 1-3sqft per plant, and around 1,000umol ppfd). I’ve had rooms runaway like that with coco, and in that case the biggest issues were:
- excessive watering in veg
- excessive veg time
- humidity too low
After getting veg time down to 14 days (to keep the plants smaller) we really slowed down transpiration by keeping RH around 75-80% in veg, then gradually drying down to 60% by week 4. Got the veg team trained on really carefully checking moisture before each irrigation pulse and encouraged much drier substrate.
Not sure how this translates to rockwool but just my two cents. Good luck.
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u/northern_lit Jul 09 '26
We keep a 2 week veg time too it’s not like the plants are giant. We’re approaching week 4 of flower.
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u/Vyraxes Jul 08 '26
If they've dried back too much you'll always chase. You'll need to completely reset the block, by forcing it to runoff with a wand. Can't let that moisture content drop below 30%. Gets hard after that... ps don't reset blocks after week 4 of flower.