Hello Professor Lee,
I’m a first time grower and I’m using a little deep water culture hydroponic system to raise a few plants in a back bedroom. I’ve been growing for almost three months now and the plants have been doing great for the most part except I’ve just started to notice that the plants’ growth seems to be slowing down and they’re getting kind of droopy and some of the leaves are yellowing and getting burnt tips. Also the roots are turning brown. Do you think I’m over fertilizing them or something?
It sounds like you have a root rot problem. It’s usually caused by the members of the water mold genus Phytophthora. This frequently happens in hydroponics systems when the water is under oxygenated and the temperature is over 72 degrees Fahrenheit (about 22 degrees Celsius). Root rot happens in soil-based systems too, but growers have to do a bit of digging to confirm the problem.
Plants affected by root rot cannot properly absorb water and nutrients leading to slowed growth and deficiencies. Most growers will throw out a plant with root rot rather than try to cure it because it will take time for the plant to recover and the condition could spread to other plants. In your case you can try to salvage your current crop with a few simple steps.
First, you will need to drop the temperature. The temperature can be lowered by increasing ventilation and circulation, adjusting the air conditioning, and / or investing in a water chiller. The ideal water temperature for your system should be between 66 and 68 degrees Fahrenheit (about 19 to 20 degrees Celsius). The cooler temperatures will discourage root rot.
Next, increase the amount of oxygen in the reservoir. I suggest additional air pumps or a stronger one with high quality diffusers. Root rot finds a high oxygen environment toxic.
You will also want to routinely flush out and clean your system. This should be done at a minimum of every two months and between each crop. I recommend more frequent flushing. For instance, I swapped out my hydroponic water every two weeks and did a detailed scrubbing between crops just to stay on top of things. Because your current crop is infected you need to do a really good job cleaning your system before you introduce any new plants.
Lastly, if possible remove any heavily damaged roots that you can and consider adding beneficial mycorrhiza to your water that will fight the Phytophthora. The brown roots won’t heal, but new white roots should begin to grow after you make the changes and the plants will recover. Some growers suggest periodic hydrogen peroxide treatments to avoid root rot. I’m on the fence about this one. While it’s true you can avoid root rot problems by using H2O2 you should be aware that it will only work for a day or two so frequent treatments are required. Also, the hydrogen peroxide will kill any beneficial bacteria that may be present.
I hope this helps you fix your problem.
I’m building my first garden and I’ve come to a crossroad about what to do with the walls. Should I use a foil like Mylar or just paint it white? All the message boards go back and forth on which is best.
This one gets argued about a lot in the growing community. I’ve tried them all: aluminum foil, Mylar, house paint, greenhouse paint, large mirrors, etc. I’ll just cut to the chase and tell you to go with the basic flat white interior house paint. While it’s true that when properly installed foils generate about 10% more reflectivity than paint, the downsides of using foils are just not worth it. Foils have to be installed very flat to evenly diffuse the light. Any crinkles will create hot spots and low light areas resulting in uneven growth or even a bit of plant burn. Foils also conduct electricity and in a small space crammed with water and powerful lights that’s a potentially deadly hazard. It’s also possible for a dark humid microclimate to form between the foil and the wall that could promote the growth of black mold which is dangerous to your health.
With paints you have a lot more advantages. A painted wall won’t crinkle so you will get a very even diffusion of light. Dry paint doesn’t conduct electricity so it’s safer to work around. And of course there isn’t any space between the wall and the paint where mold can develop. Add to this the fact that if you scuff your paint or wipe some of it off a surface you can just add another coat and problem solved. Flat white is the most reflective, eggshell is a little bit less reflective but easier to clean, glossy is the least reflective, go figure, but is the easiest to clean.
I liked to tack up cardboard or plywood sheets and paint them white so when it came time to break down my gardens I didn’t have to repaint a permanent wall or two. That’s a good piece of advice when you’re renting an apartment or house and have to quickly return it to its original state before moving.
Slugs are eating my plants. I started my plants indoors and transferred them outside a couple days later I discovered they were being eaten alive by slugs. I pick and squish ‘em as I find as soon as I find them but I’m losing the battle. What should I do to get rid of them once and for all?
Sounds like you have a real slugfest on your hands. I hate slugs – they are destructive little suckers. There are some home remedies you can try like burying some drinking cups in your garden up to their rims. Then pour a couple inches of beer in each cup. The slugs are attracted to the smell of the beer, then, when they crawl inside the cup of beer, they get drunk and drown. You’ll have to change the beer each night (and you cannot drink it either because the dead slugs make it taste awful). You can also place a few plates of salt around your plants. The slugs will investigate the salty smell and die as the salt pulls the water from their bodies. These methods do work and will help to manage the slug population as long as you keep it up and accept the fact that you may not rid your garden of every single slug.
In my own outdoor gardens I like to pour diatomaceous earth around my plants. Diatomaceous earth can kill slugs in 24 to 48 hours. I’ve also used organic baits to rid my garden of slugs for two or three months. These baits usually come in pellet form and are widely available at most garden stores.
Good luck, slugger!
Hello Professor Lee,
I have a plant I want to grow again. She is the best I’ve ever grown and I want to clone her. I’ve heard that you can regrow a plant by just lengthening the light cycle again. Is it really that simple or do I need to do anything else?
Yep, it’s pretty much that simple. What you’re talking about is rejuvenating a plant so you can turn it into a mother. When you extend the light cycle the plant will revert to a vegetative growth pattern and at that point you can take cuttings from it. If you’re growing in soil it helps to flush the soil with some clean pH balanced water and then start with a vegetative NPK fertilizing schedule. Hydroponic systems are even easier to switch back to a nitrogen-based fertilizer.
After you harvest your plants try to keep as many leaves and smaller bud sites on it as possible. A couple of weeks after you switch the lighting cycle, new growth should be developing. These early leaves may be single bladed, smooth edged, and twisted. This is normal and will correct itself quickly. Once the plant is actively growing again you can keep it as a dedicated mother or start one with a cutting. Either way you will soon be able to fill your garden with your favorite plant over and over again.
On a side note some growers like to get a quick second harvest by rejuvenating plants for a month or so and then switch them back to flowering. I’ve done this before and it was quite fun, but I don’t suggest trying to do it time and time again with the same plants as they can only take so much before the quality starts to go down and the likelihood of developing pathogens goes up.
Keep those questions coming! I’ll answer them for you as quickly as I can and you might even get to see them published in the next issue of Weed World Magazine! This time around I sent Alex a copy of my book Marijuana 101: Professor Lee's Introduction to Growing Grade A Bud. At some point we all encounter our first setback or challenge and it’s at that point that we either give up and quit or figure it out and keep on growing.
‘Till Next Time, Happy Growing Everybody!
This article first appeared in isse 124 of Weed World Magazine