After One Week, Cannabis Stopped Growing

by Ed
(Exeter N.H.)

A digital indoor/outdoor thermometer helps a lot to keep temperatures in the grow room just right
Let me start off by telling you a little bit about my set up. It's a custom made grow box that's 2'x2'x3', lined with mylar, and lit with eight 26 watt cfl's. I have two 55 cfm computer fans (one fan per intake), and a 4 inch inline fan for an exhaust. The temperature stays around 78-82 degrees F, the humidity stays at 36%-40%.

FoxFarm Ocean Forest is my 'go-to' for the base of my soil mix for all my plants that are two weeks old and older
I germinated my seeds in a wet paper towel, and after they popped open I planted them directly into Foxfarm Ocean Forest soil. After putting them into the box they grew good for about 3 to 4 days, then stopped. The leaves are turning pale in color. I haven't added any nutrients to the soil, just watered them daily with distilled water (about 6 oz to a 1 gallon pot). I was thinking that the soil maybe too rich? Should I be starting my seedlings in that type of soil?


Thank you very much!


Answer: The yellowing symptoms you describe are worrisome indeed! The same symptoms can be from any number of things....too many nutrients, too few nutrients, a pH problem (causing too few nutrients to be available), temps too cold causing wilt or powdery mildew, and even light poisoning! And I'm sure this is a short list!

You already have a thermometer, and seem to have your temps in check. This is a huge help for me, trying to figure out your exact problem remotely. As long as the temps have been no lower than 58 degrees F at night and no higher than 85 or 90 degrees F in the day, the temps are not likely to be your issue. Consider yourself ahead as a grower for having this base covered!

FoxFarm planting mix, in the red bag, is more friendly to new seedlings and fresh clones than the Ocean Forest mix (which is a little stronger)
Another big help here....I have some personal experience with the FoxFarm soils. I had a good friend who used to use Ocean Forest all the time, but ran into a batch of clones from one particular strain that put out sensitive clones and seedlings. He began starting his clones out in the red bag of FoxFarm first, and transplanting them into FoxFarm Ocean Forest later on as they went into bigger containers. My gut tells me this is not your problem either.

Every drop of water and nutrient solution should be adjusted to a pH of 6.2, where maximum nutrient availability occurs
All FoxFarm planting mixes that I've ever purchased have been between a pH of 6.3 and 6.8, which is basically ideal. It is possible that your tap water has an alkaline pH, but it would have to be severely alkaline to cause a problem with your freshly sprouted seedlings in just a matter of days. It is easy and very affordable to test (and correct) the pH of your water and nutrient solutions. Every drop should be adjusted to a pH of 6.2 before being given to your plants. This is critical, but I do not believe this is your main problem either.

It's extremely difficult to poison cannabis plants with too much fluorescent light. I'm crossing this one of the list without even considering it any further.

It's very easy to over water young seedlings. At first, there are very few roots compared to the quantity of soilIt's important to be very careful with the delicate roots of young seedlings. Pushing i.d. tags into the soil and other disturbances can do damage below ground. The result will always be some kind of damage above ground as well. Root damage can cause yellowing above ground, and worse! For now, I'm going to assume that no traumatic soil disturbances have occurred.

For certain, change to the FoxFarm planting soil. Be sure to check and adjust the pH on every drop of water and nutrient solution you give to your plants. Continue to keep those temperatures in check day and night. However, I feel the key to your garden problem lies in the following clue....you say you "watered them daily with distilled water".

As soon as seedlings pop open and begin growing, or clones pop roots, it is time to get them on a feeding schedule! Immediately they can handle a feeding of 1/4 strength nutrient solution. This will depend on the kind of plants you are growing, and also a little on the strength of the light you have them under. For young cannabis plants under 40 or 50 watts/sq.ft., this will a nutrient solution strength of 400-600ppm. Once you feed them the first time, make sure you feed them once a week from then on! Always keep these habits the same so you always have an idea of how much food your plants are getting. This will help you develop some idea of what you should be expecting from your plants as they grow and flower out.

Over watering can cause yellowing, fusarium, pythium, and stem rot. Many symptoms mimic symptoms of other problems in the grow room, making the problem difficult to diagnoseAnd this is the most important part: try to only water them once per week when you are feeding them the nutrient solution. Keep an eye on your garden daily. If you see any plants begin to wilt at any point in the week, go ahead and give them a few ounces of plain water....but only enough to get by until the next regularly scheduled watering! Your plant containers should be drying out considerably in between waterings, and if they are not, then plants easily become over watered. This is especially true with new seedlings. At first, there is a lot of soil and only a few small roots. I hope this helps you out Ed, and Happy Growing!

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