Expert Q&A: Growing Cannabis

Got a question about growing marijuana? Let me know below and I'll try to answer to the best of my ability. Noticed I've been getting some questions on other posts, so I figured this could be a great place to have a question/answer thread going. Ask away!

131 replies on “Ask Me Anything”

I have a 5x5 gorilla tent with extension 1’ a tarantula 5x5 tent led. Ultima. from grand masters what cfm filtration inline system do i need

After falling for ‘just buy a bag of this soil - it’s all you need’ ploy… my first attempt at cannabis growing died a spectacular death in a nitrogen seize and curled up like the toes on the wicked witch’s shoes in Oz.

So… it’s grow number 2. I watched a whole bunch of Build a soil videos and today….

I mixed my first soil. About 1/3 good humus, 1/3 perlite/peat 1/6 castings and 1/6 “kitchen sink” - myco, bacillus, azomite, bone meal, DE, Gaia Green 4-4-4…. -a handful of this, a pinch of that.
I know it sounds crazy, but I blended until it ‘felt’ right to me.
It’s in an under the bed sterlite tub with the lid on loosely. I stir through it several times a day.

It feels happy and the smell is intoxicating.
I squirt some crudely made earthworm castings ‘tea’ on it if I think it needs it.

I have some fermented banana water from 3-4 months ago, and I’ve started adding to it.

CAN I SQUIRT THAT ON THE PLANT?
DO I NEED TO DILUTE?
CAN I USE IT IN MAKING SOIL?
I don’t want to ruin this beautiful soil!

OH- and how long should it ‘bake’ before using? I was hoping to use it in a week or two.

AND… the soil doesn’t clump yet if you pick up a handful and squeeze.

Part of me wants to add a bit more (very wet) humus so the soil is a bit more ‘squeezable ’. But that will make it heavier, retain more water, slow the dryback time and encourage pest activity, which is Bad..

I’m going to do this grow in felt bags. I tested felt bags out on a 2 year old 4” basil (yes, 2 years) with about 4 pale yellow leaves. In 72 hours it was a brand new plant after being stuck in my new soil mix in a felt pot. You can tell it’s good for building a healthy root system, and it’s so much easier to tell when it’s watered. (I’ve been bottom feeding.)

Anywho, I’m crossing my fingers and praying.

Am I on the right path?

Can you point me to some resources/advice?

I feel “ no soil, no soul.”

Thank you

Hi Susie! It sounds like you've learned a lot from your first attempt!

Mixing your own soil blend is a great step.

Regarding your questions about fermented banana water, yes, you can use it on your plants. Just make sure there's no mold in it. I have a guide here: https://drcannabis.io/banana-tea

For how long your soil mix should "bake", letting it sit for at least a week or two should be fine.

Adding more humus to your soil mix to make it more "squeezable" could be a good idea

Using felt bags for your grow is a good choice as well.

When you set up a ventilation system inside a small tent (2 x 2 x 4) -- do you have to have the fan and exhaust constantly running? or can you put a timer on it? what do you recommend?

Hey Bryan! You can use a timer for the fan and exhaust. Just make sure they run for a significant portion of the day, and make sure temperature and humidity are within acceptable ranges.

Yellowing leaves with a ginger tint during the second week of budding can be concerning.

  • Nutrient Imbalance: It could be a deficiency, possibly of nitrogen or other essential nutrients.
  • pH Fluctuations: Incorrect pH can lock out nutrients.
  • Overwatering or Underwatering: Ensure your watering schedule is consistent.
  • Light Intensity: Too much light can cause leaf discoloration.
  • Pests or Diseases: Check for any signs of infestation or mold.

Monitor your plant closely after making adjustments, and let me know.

Hi Dave! We do not provide seeds, but I can offer you some recommendations: Girl Scout Cookies, Purple Punch, Gorilla Glue #4, Gelato, Mimosa. I would recommend reaching out to seed banks or dispensaries and discussing your needs with them.

Hey Santiago, I've got a unique, unknown OLD strain that I crossed many years ago from an old farmer in Kentucky. I've done it indoor, outdoor, and a few through Hydro, they all do great!!! Somehow this round my mother, which started from seed. Is NOT doing good at all, I'm triple checking PH today but I'm at a loss. It seems like Nitrogen issues but when I try to correct it seems like it gets worse Lol I'd love to send you a few pics or post here but don't know how too. Trying to explain through text would just be a waste of time, sending pics or posting is the only way I'll convey the real issues. HELP???? Lol

Hey Josh! I can totally understand how frustrating it must be to experience. You can send me the pictures at [email protected]. In the meantime, aside from checking the pH levels, consider revisiting your nutrient regimen, and ensure there's no root rot or pest infestation causing the problem. Sometimes, flushing the system and starting fresh with the nutrients can help. Keep a keen eye on the plant's response to the changes you make to avoid worsening the condition.

Cloning a female cannabis plant will indeed produce female plant. There isn't a chance for it to produce a male plant since it carries the exact genetic information of the mother plant.

I’m an experienced grower, but we all have mishaps, I have 23 day old seedlings, their baby leaves are starting to become bright a bit like yellow

Hey Erick! Given that they are only 23 days old, they are still quite young and it's a critical time. I'd start here:
- Check the pH of your soil between 6.0 and 7.0.
- If you're growing indoors, make sure your seedlings aren't getting too much light.
- Consider preparing a mild nutrient solution suitable for seedlings.
- Ensure that your growing medium has good drainage.
- Take a close look at your plants to make sure there are no pests infesting them

Hey! Yes, you can use those natural additives for your cannabis seedlings, but with caution. Bonemeal: you might want to start with a light sprinkling on the soil (very light). Banana Peel Tea: Use it sparingly for seedlings, perhaps once every two weeks. Instant Coffee: be very cautious, too much can harm seedlings. Use it sparingly, perhaps a quarter teaspoon per gallon of water, and not too often, maybe once every few weeks.

Hello, Ok! I have soil ph problem!! My fault, stopped checking ph, because it was always spot on. Now 1 week into flowering, ph us riding at 7.5+ - 8. Plant is slowing down new leaves have a curl to them at tip, upwards and a bright yellowish green vein on some older leaves. It doesn't look that bad, compared to ither prinlems i've seen peeps have. I need soil ph to come down quick, trying to amend, it's not working fast enough. Question issss.... Should I repot in new soil with a good ph so my flowering doesn't suffer from not uptaking nutes? Or is it a different problem not caused by my PH. None of the photos look exactly like mind do. Iron def. I believe looks the closest on the new leaves, brighter green looking color. None are white. Any help or advice, please! Ive never had a plant go into shock when repotting. Im gentle 😁

Hey there! A pH imbalance can certainly affect nutrient uptake, leading to symptoms like those you've described. While transplanting is an option, it could introduce added stress, especially during flowering. Instead, consider using pH-adjusted water when watering. You can also try a light flush with pH-balanced water to correct the soil's pH more immediately. Monitoring the pH regularly afterward will be crucial. Remember to always be gentle with your plants and keep a close eye on them to see how they respond! 😊

Santiago, I struggled with a magnesium deficiancy in 1 of my girls. I finally figured out the problem and treated her 2x but ran out of time, because it was time to harvest her. She looked terrible but still had buds. Some of the branches aren't effected and look good, but the majority has dark spots on leaves. Will the buds be ok to smoke on this girl? P.S. This is my first time growing.

Hey there! It's great to hear that you've identified and worked on addressing the magnesium deficiency. To answer your question, while magnesium deficiency can hinder overall plant health and the buds may have a slightly off taste, it doesn’t mean they’re unsafe to consume. However, always trust your senses: if something smells or tastes off when you sample it, it's best to err on the side of caution

It sounds like your plant has nutrient imbalances and possibly pests. Check your watering schedule, ensure proper nutrient levels, and inspect for pests. Addressing these can help revive your plant's health.

Hi Penny! In nutrient-rich soil, begin adding nutrients after 2-4 weeks at reduced strength (1/4 to 1/2 of the recommended dose). In soilless media, start providing nutrients immediately at a lower concentration, increasing it as your plants develop. Keep a close eye on your plants, adjusting nutrients as needed, considering autoflowers' shorter life cycle. Happy growing!

Hi Al! The right time to begin using nutrients for your plants depends on your growing medium and nutrient type. If you're using nutrient-rich soil (like many commercial potting mixes), your plants will use the existing nutrients for the first 2-4 weeks. After that, start adding nutrients at a reduced strength (about 1/4 to 1/2 of the recommended dose) to prevent overwhelming the plants.

For soilless media (like coco coir or hydroponics), which lack nutrients, start providing nutrients right away at reduced strength. Gradually increase the concentration as your plants grow and develop.

My plants are very healthy. Using f f microbial solution, f f soil , and the trilogy of grow and bloom nutes. They are only 4-5 weeks into veg. I know enough to keep the levels low. My issue is I have some brown/copper spots on a few leaves. Maybe over spill from my last microbial watering? Or am I not giving enough nutes?

Hi Peter! The brown spots may be related to the microbial solution if it was applied excessively or unevenly, causing localized nutrient imbalances. However, it could also be due to a nutrient deficiency or nutrient burn if the feeding levels are too low or high. To identify the cause, monitor the new growth on your plants. If the issue persists or spreads to new growth, consider adjusting your nutrient levels and the usage of the microbial solution. Keep an eye on pH levels (6.0-7.0 for soil) and avoid overwatering, as these factors can impact nutrient absorption.

Hi Grumpy! It's generally better to water and feed your cannabis plants during their "morning" or the beginning of their light cycle. This is because plants use the water and nutrients more effectively during their active photosynthesis period when the lights are on. Watering at the beginning of the light cycle also helps reduce the risk of mold and mildew, as the excess moisture can evaporate more quickly during the day.

Hi Earl! Slowed growth in autoflowering cannabis plants could be due to several factors, and defoliation might be one of them. Autoflowers have a shorter life cycle, and they can be more sensitive to stress caused by defoliation or other high-stress techniques. It's possible that the defoliation has stressed your plants, leading to slower growth and smaller leaves at bud sites.

Hi Cheri! I don't have pictures to share right now. Symptoms of calcium deficiency include distorted new growth, necrotic spots on leaves, brittle leaves, and stunted growth.

Thanks for having me. I just wanted to know if you ever combined a LED/HPS/MH together? Or hybrid as some call it. I'm looking for results from other growers but I can't seem to find any. So next month I'll be putting my gals into flowering and then I'll purchase either a 600W 10K MH or two 315w 10K CMH bulbs for the last few weeks of flowering.

Hi Ricky! Combining LED, HPS, and MH lights in a hybrid setup can be beneficial. Each light type has unique advantages. I haven't personally combined all three, but some growers have. You can use LED as the primary light and supplement with HPS or MH during different growth stages.

My end product still taste like peat moss (baacto brand organic amendment only filtered water with Dr earth bloom for bloom 5gal fabric) what can I add to it to get the peat moss taste out or will I have to get all new soil?

You can try adding other organic amendments or fertilizers to the soil mix to help balance out the flavors. Some growers recommend using worm castings, bat guano, or kelp meal to improve the overall taste of the buds. Other than that, you may want to consider changing the soil mix entirely. Consider using a soil mix that is formulated specifically for cannabis and doesn't contain peat moss. You can also try using a hydroponic setup, which doesn't use soil and allows you to control the nutrient levels more precisely. Unfortunately, there is not much you can do to change the taste of buds that have already been harvested and processed.

Hello, indoor growing is getting expensive. Does $800/month sound right to light up a 4x6 veg tent and a larger flower tent. The lights are LED 550 watts .

Hey! $800 per month for electricity sounds high, especially if you are only using LED lights. You may want to compare your electricity costs to others in your area, or to consult with a electrician to assess your setup and identify any areas where energy efficiency can be improved.

The length of the vegetative stage can vary, depending on factors such as the strain, growing conditions, and personal preference. A 6-week vegetative stage is a common choice, but some growers may opt to extend it to 8 or even 12 weeks. The choice of veg length ultimately depends on the desired size and yield of the final product.

All my curing flowers are smelling the same like a chemical smell is this from not burping enough if so can I correct the problem or are they a total lost or is something else all togetter

It's possible that the strong chemical smell is due to not burping your flowers enough during the curing process. This can lead to a buildup of moisture and gases, which can give your flowers an off odor. You might try burping your flowers more frequently or increasing air circulation around them. This will help remove excess moisture and prevent mold or bacteria growth, which can also cause strong odors.

It's also possible that the chemical smell could be caused by other factors, such as contamination from pesticides or other chemicals, or exposure to plastic or synthetic materials during the curing process. In that case, it might be best to discard the affected flowers and take steps to prevent similar issues in the future

I, have learned more from this site then i have in the last 8 mouth. reading other one's pictures are great

big leaves on my laughing budda have turned purple on one plant, cant find it anywhere to know if its a deficiency or over done one a nute? started at base and moved out. any ideas?

The purple coloring of the leaves could be a sign of a nutrient deficiency, such as a lack of phosphorus, or it could be a result of over-fertilization. Other possible causes of purple leaves include exposure to cold temperatures, genetics, and or even disease. Test the soil for nutrient levels and check for any signs of disease or pest infestation.

I'm growing a blue dream auto and have contracted a couple of problems there are leaves that seem to show potassium def., edges and edges turning brown, and the other appears to be calcium def. brown/copper spots on the leaves, mostly leaves closest to light. I'm flowering at about 9wks. Is it possible to have both def. at the same time?

Yes, it is possible for a plant to have both potassium and calcium deficiencies at the same time. This can be due to a variety of factors such as an imbalance in the soil, over-fertilization, or improper watering. To correct these deficiencies, I would flush the soil and provide the plant with a balanced fertilizer that contains both potassium and calcium. Just be careful not to over-fertilize, as this can lead to other issues.

I have translucent spots on the leaves and I don't really know the reason. I'm going to lose my mind because of thinking about the reason.

Most like some kind of bug. Start by going to Google images and look types of bug marks on leaves, see if you find one that resembles yours

I am about to build a grow room outside. I'm building a 10 x 20 'chicken coop' where 2 10 x 10 rooms will be connected through a doorway inside the chicken coop. I live in Arizona where it gets very hot during summer months so I plan on an air conditioner for the grow room. I will pull the air into the chicken coop room for ventilation. I plan to install a sink in the room and will have ample electrical supply. I may need supplemental heat for the winter months. What is the best way to control and measure the humidity? A swamp cooler?

Swamp cooler seems like too much for me. I'd go for a humidifier or dehumidifier to not impact the temperature so harshly, and leave the AC to manage that.

Hi
I have searched for the leaf mutation I am getting but can't find it anywhere
It's strange.
I have pics and would like you to see them
it's like the fan leaves are developing uniform holes and there's a strange light-colored growth near the holes then the leaf blade seems to lose its middle down to the rib of the leaf'

the only thing I have changed recently after a bout of root rot is some beneficial bacteria two types well under the recommended dose for my size tanks

Can you help?

I have a plant with leaves that kinda look like feathers. Thats the best I can explain it. It really needs to be seen. Looks very tropical. Any I.D. on strain or reason ?

Can you upload a few pics to Imgur and share the link with us? I don't think I've seen that before

what is the real truth about growing in the desert (tucson) outdoors in the summer?
can you please suggest some varieties that can handle the heat...sometimes 112 degrees?
thank you for your help!
j!M

Try asking or researching at a Seedbank. They share the specs for every strain including how they handle heat and how much they can handle

Hello I was reading your article regarding urine. I have kidney failure and unfortunately live with extremely high protein in my urine. Is this protein available something g similar to the lines of bone meal preiteins etc as rich amino acids or will it kill everything I wee on.

Sorry about that! I really have no idea, I haven't found more info about urine other than what I have already covered in the article. Sources insist on not using urine unless you're healthy

Need help! Leaves started yellowing and browning in patches, PH was a bit low. Added a little calcium to the next watering and the problem stopped. BUT not growth has slowed a lot.
I will email you a picture with MICHAEL R. as the subject?

Thanks for emailing me the pictures.
Looks to me like excess salts on the roots. I'd check pH and flush the roots with abundant water.

Main problem is my auto flower WW!! Followed recommended nutes on the flora trio bottles but seems like it’s not enough when she started blooming. So I upped the potassium with koolbloom but still seems like she’s not getting enough ( from recommended dosage on bottle). I am about ready to pour the whole bottle on the pig just so she does right :/ should I keep upping it more or will that be to much and just let her ride. Just don’t want her to die on me so close to harvest

Don't do anything harsh and use your best judgement. Go little by little and remember that not every crop is going to be perfect.

They need more light! They stretch like that cause they're trying to get closer to the light source (don't get them too close our you might burn them)

A friend has been growing bubba kush from mid May of last year and she still hasn’t harvested it yet! From what I’ve read, 9 weeks is the max flowering time. How will this effect her crop?

Started 12,12 few days ago, leaves started to look a little white at the veins, new growth looks fine, grow outside for 30plus years, been trying my luck inside for 1plus years,big difference can't seem to get it dialed in, had decent bud, but no size as to the pitchers I've seen

This is one of the most helpful sites I've found online. Your photos are awesome and seem to accurately describe what is actually happening to the plants for diagnosis. This is awesome. Just saying.

Hi, I live in Florida and want to move out of state. I'm as MMJ patient and I want to move where I can grow my own legally. The stuff they pass off as medical grade here is horrible! Some Monsanta /Bayer/landscaping plant concoctions. They ruined flower down here. What state would you suggest? I just want to grow my own. Thanks for any suggestions, Judy

Im a long time grower from 18'-40 on and off, i have grown 1000s of plants, but im still learning. I currently have 2 plants that are in reused soil that has been used many times simply reamended with organic inputs. I have red stems i have seen many times but the red continues up between the line in the middle of many of the leafs. I really dont know what it is. I do get soil test done useually especially when working with bigger amounts of soil. But did not this time as i only used old soil on those two pots and two pots got new soil. The plants in new soil do not have this issue. Im thinking i got to much of something making something else not as avalable. When using old soil we don't know whats higher or lower in npk, mineral, vitamins etc... maybe im lacking something not sure. Any thoughts on what can be causing this? Im into week 3 of flower.

If you don't know what's in the soil then that's most likely the problem. If you're going to use old soil you should treat it properly before starting a new grow. I'd flush it with abundant water and start again the feeding process

Hello.

I switched my plants to flower; and they started to lose more and more the greenish colour.

At first i believed it was lacking N so i started giving some more grow nutes to it again. Then i added some pk1314 incase it was having a deficiency o P, to just yesterday i added some calmag as i'm lost and don't know what's wrong with my ladies.

watered at ph 6.5-7 grow medium Plagron Lightmix (soil) nutrients used Plagron terra range

https://imgur.com/a/8GFwzcu 2 pictues have 9 days of difference in between.

Thank you

Yellowing during flowering stage is usually related to Potassium. As Nitrogen is less needed during that stage.

Since you've already added too many things. I would wash the substrate, remove all nutrients and re-start the feeding process.

Please refer to a tutorial on how to feed during flowering stage, Potassium and Phosphorus are most needed during the flowering stage.

Or even better, get a commercial fertilizer that comes with everything you need for growing big buds, follow the instructions is the bottle and you'll be fine most likely.

Hey bro. Sorry you having issues. I would check your runoff ph and EC/ppm. If ph is off it will lock out nutrients. If EC above 1.4 I would flush with ph water. 3times the volume of your pot. Example 1gal Gro pot=3gal water to flush. If EC is low Either top dress or buy some bottle nutrients. Hope this helps

High Sanchy, ive got a problem with one of my plants but I don't see anything in your collection that looks like what I have. I wanted to send you a picture or a video but don't see where I can add it. Can you send a link I can send one to?

Can I send a pic of my leaf so you can see my issue?
It seemed to start in veg after I gave 1 dose of organic nutritiants.

Impossible to know without pics or maybe looking at her up close. There might be a problem with the roots or the substrate. Start by chcekcing that the pH is within optimal levels

This is the best breakdown of deficiencies and symptoms I have found. All the extra photos really help and I’ve been doing this for a long time!! Great jive and thank you!!!!!!

I didn't know there were "kinds" of bone meal. Try to search about diluting the bone meal in water so it'll absorb it faster than just spreading it on the soil (most likely)

Thanks from me and my old "grand daddy purple" strange thing to call a female really but that's another story. Great information, brilliant format easy to navigate... happy campers all round!

Try Grandmommy Purple...IMO&E, it puts all the GDP I've worked with (&seen) to shame. Happy Glowing!!!

Depends on her stage. During Vegetation likely Nitrogen deficiency. During flowering likely Potassium. Check out the Symptoms page for images and depictions.

This is very helpful I had a cal mag deficiency wipe out 20 plants outside this year from the cal mag deficiency came bud rot I am new to mixing coco or Pete moss to my soil and didn't realize I had to use it outdoors the plants were fine beautiful 7 and 8 feet tall big bushy girls then it all went to crap bud rot or something made em look like a torch was taken to them

Urine As Fertilizer For Cannabis did you do it ... me over 8 years of doing this ...avoid bad odors ??? i never had bad odors ...........or bugs

You upload it somewhere else and add the link to your comment. Any social network would work. Other than that you can Google "image upload", they're easy to use.

i fertilized my plants and for the past to days have gone to a 12/12 cycle. My plants were very healthy looking and overnight the leaves drooped and some felt dry? Not sure what happened, any suggestions? let me add that i have also just topped the plants in the past several days

Sounds like you did too much fertilizer 😕 and the stress from the topping might have done it's part when combined. Hopefully you can take care of them and they'll recover. Google about flushing the roots to get rid of the excess fertilizer and be very attentive to them for the following weeks.

Nice article honestly, the issue I always run into is the abundance of opinions of what “it could be.” Youtube is the worst and so myself being a more visual learner pics of exactly what my leaves look like, for instance nitrogen toxicity, are great for people that are searching for answers.

Many Thanks

Hi, I seem to be having a problem that o have not seen as common. My plants are extremely slow growing and all new leaves start turning pale/pink white and then die. I have flushed and ensured I gave nutrients. Any ideas?

I'm not sure what would turn marijuana leaves pink. Maybe it's too cold? Either that or something with the roots or the soil.

Rust Fungus is an odd topic, but I just got some pics of the weirdest rusty/moldish growths on my White Widow's. I cut those mothers off, doused em' in Neem Oil right before the lights went out, and now praying for the best. I'm bringing this up entirely because I think it could be helpful to you and your quest to help the cannabros/cannababes:
It spread like wildfire. The red flag showing me that it wasn't nute problems was the fact that it had spread from lower, older leaves to young and seemingly healthy new growths. Sure, everyone's grow environments are different, but this particular event was an indoor grow, mylar tent, correct to the T fresh air exchange, with a low RH of 45%, and temperatures staying between 77 and 82 degrees Fahrenheit.
My theory on how the growths started is that when my lights go off, I do so timely with my bed time. That being said; I cannot truly check where the RH% and Temp lie in the middle of the night. It has been storming quite frequently where I live, and I believe my RH% has been sky rocketing over night. That fluctuation of Low/High Temps and Humidity may have caused this form of fungus to grow, but all I have are pictures of my own, and the occasional post on how Rust Fungus hasn't been scientificly proven to spread to Cannabis.
If you have any info on this, please let me know as quickly as possible! My girls lost a lot of foliage today and if there's a round two I want to have a ballpark guess on how to fight back!

Hey Joshua, so sorry to hear that. I haven't faced or investigated rust fungus. But I can see there's a lot of information online just searching "rust fungus". I pray your plants will recover!

Rinse your plant Thoroughly. Ensure your pH is right.
1/Rinse your soil.
2/PH all your water before watering.
3/Do not use excess nutrients.
4/Make sure you’re using a fan.
5/If possible, keep your humidity levels relatively low.
6/(I use) Neem oil with a touch of vinegar to correct my pest and fungal problems.
Spoonful of Neem oil and a spoonful of vinegar to a quart of water, shake vigorously before using.

Then most likely the problem is in the roots. Check the pH of the growing medium. If soil, also check pH of the runoff water. Also check symptoms of root rot and excess salts

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Santiago
Santiago
Hey there, I'm the person behind this website. I started growing cannabis in 2014 right after marijuana was legalized in my home country. Today, on drcannabis.io, I address growers need for knowledge and show you how to grow cannabis plants and enjoy amazing buds.

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