Professor Lee,

I have a question about an article I read about determining the sex of cannabis seeds. I was wondering if there was any truth to it, and I would appreciate your thoughts on the subject.



Hello Mitchell,

I have heard of this but never tried it myself. Most growers just accept the fact that on average, non-feminized seeds are roughly 50 percent female and 50 percent male. I’ve discussed sexing marijuana seeds with some growers who claim that this technique does indeed work, but just to settle things, here’s what we can do. I want to ask all the Weed World readers that are about to start some new plants to take a few moments to examine their seeds and help us figure out if it’s possible to pre-sex the little buggers. 

Here’s the theory: Every seed has a hilum, basically the seed’s belly button, where it was attached to the plant while it developed. Female seeds supposedly have a nice round hilum shaped like a small volcanic crater. The males are said to have a smaller, less defined hilum that may be shallow, deformed, and/or resembling a slit. Anyone interested in helping, or satisfying their own curiosity, should take note of what kind of hilum their seeds have and then separate the seeds accordingly and mark each plant’s container with the supposed sex. After the plants present their flowers we’ll know if it’s true or not. If you’re using feminized seeds please take note if they all have well developed hilums or not.  This would be useful information as well.

Please contact me on Twitter @ProfessorLee420 or on Facebook at with your results. I’ll be sure to report the findings in a future issue of Weed World. I look forward to seeing how this works out. 

Thanks in advance,

Professor Lee

Hello Professor Lee,

Can I ask another question on clones? We have done some cuttings and put in rockwool with root powder, but after three days the stems are soggy and rotted away. What can cause this to happen? 


Hello again Gerard,

Here is a rambling answer to your question.  

My first guess would be an infection. It is important to sterilize the rockwool before using it and to keep the instruments and cutting area clean. A good soak in water with hydrogen peroxide or another sterilizing agent will work well for the rockwool. Use alcohol to sterilize any scissors or razor blade before/between taking cuttings. Also, properly sterilize the cloning box they’re being rooted in and use distilled water in a sterilized spray bottle to mist them with. Oh, and wash your hands with soap and hot water and/or wear disposable gloves. Keep the time between making the final cut and the insertion into the rockwool to a minimum; if you take too long the cut area can dry out a little and the clone won't be able to uptake water effectively.  

Hope this helps. Please keep trying! Most growers eventually get a near 100% success rate with cloning.  It just takes a few batches.

Good luck,

Professor Lee

Hello Professor,

I have a simple question about what humidity I should keep my plants at. Is it the same from start to finish, or should I change it as I go?



P.S. This will be my first grow ever! 

Hello Michael,

Congrats on your first grow! You’re in for a lot of fun.

For vegetative plants I recommend maintaining your humidity levels at between 40 and 70 percent. When you are ready to flower, try to keep things around the 45 percent mark. Young plants can usually tolerate quite a bit of variation, but proper humidity levels are extremely important during the flowering cycle. If it gets too high you’re inviting the dreadful bud rot into your garden. A simple humidity gauge is available at any nursery or grow supply store. I always had at least two in my gardens. Most private growers can solve any humidity problems with a good ventilation system. Sometimes a grower may have to invest in a dehumidifier. 

These things can sometimes be a challenge for new growers, but you’ll soon discover that we can be determined and creative people. I always welcomed a challenge and felt great when I could figure these things out. 

I hope this helps get you started.

Professor Lee

Hello Professor Lee,

I think my plants might be sick. I have a couple of plants in my garden that are taller than the rest and seem to be growing pretty well, but the lower leaves are getting pale. Some are pretty yellow and there are dead spots on them. Also, the stems are turning red. I thinned my lower growth some time ago and the leaves in question get plenty of light. I’m trying an organic soil mix I bought at my local supply shop for the first time and the plants are about two months old. They’re in three gallon pots and I haven’t seen any bugs or smelled anything rotting. Could they have a virus or something? 


Hello Luke,

It sounds like you don’t have a virus or other bug, but maybe a potassium deficiency. Plants low on potassium will have these symptoms. Organic soil mixes are great, but the nutrients in them are finite and eventually plants will munch their way through them and need a fertilizer boost. You can make up an organic tea with either bat guano or kelp meal to solve the potassium problem, but this could be a sign that your other nutrients could run out pretty soon as well. I suggest you try a tea that will cover all the major nutrients: nitrogen, potassium, and phosphorus. A good mix would be something like worm castings and alfalfa meal. Worm castings are great because they have beneficial fungus and bacteria that help the plants. You could just use alfalfa meal if you want, which is what some growers do, but I prefer a more interesting blend of kelp meal, cottonseed meal, and soy meal. If you do use the cottonseed meal in your tea be sure to use organic cotton sources. Commercial cotton growers use some of the highest levels of pesticides in agriculture which can wreak havoc with an organic grow. 

The best way to prepare a tea is to place your ingredients in a bag of some kind; a nylon stocking or cloth bag will work very well. Next, soak the bag in a bucket of water for a few hours. It helps to add a single drop of liquid dishwashing soap to break the water tension and allow the water to fully penetrate into the organic mix. Every hour or so dip the bag in and out of the water to enrich your water mix. When ready, just drain and remove the bag then water the plants with the mix and the problem should correct in a week or so.  Use this fertilizing method every second or third time you water the plants to prevent future deficiencies. 

I hope this helps!

Professor Lee

Hello everybody,

There were a lot of really great questions this time around. In this issue I sent Luke a copy of my book, Marijuana 101: Professor Lee's Introduction to Growing Grade A Bud. Figuring out what could be wrong with a sick plant is pretty hard to do and can be confusing, or there might be more than one thing going on. Please keep the questions coming and next time it could be yours that I pick for an autographed copy of my book.    

Happy growing!

Professor Lee

 This article first appeared in issue 115 of Weed World Magazine