How to Foliar Feed Marijuana
Foliar Feeding is our focus in this week’s How to Grow Pot series where UK expert herb grower, Mel Thomas, the author of Cannabis Cultivation: A Complete Grower’s Guide, 3rd Edition, answers your questions. Mel’s a world-renowned cannabis cultivator and at one time was the largest producer of marijuana in the UK. Have a question for him? Then email us at stuffstonerslike[at]yahoo.com.
Question: Can you give me some advice on foliar feeding? When to do it, what to use and if it’s even a good idea or not? I’ve read a few different books and have searched for some tips online, but everything seems so contradictory, especially what I’ve found about foliar feeding plants that are flowering. Should I do it when the lights are on or off or just about to turn on or off? One more question, can we use the nutrients in our reservoir? We’re growing in coca and perlite and have grow nutes in the resivoir: General Hydroponics micro, grow, bloom as well as some Roots Excelurator, Superthrive, Floralicious Plus and Diamond Nectar all in there. Can we just mist this concoction on the leaves?
Mel Thomas: There is a lot of misinformation spread about foliar feeding, but I recommend it as a cost effective and direct method for providing nutrients to the crop and it also works as a minor preventative measure against spider mites which are sensitive to nutrient sprays. Spray as soon as lights go on, during the middle of the day it is less effective, if you spray at the end of the light cycle the moisture will not be absorbed and may cause fungal infections. Spray the underside of leaves for all of the nutrient application to reach the stomata and gain the most efficient nutrient absorption. You can mist the plants again with fresh water once the nutrient appears to have been absorbed to wash of any salt deposits that may build up.
Formula Recommendations for Foliar Feeding Marijuana
The following recommendations are based on organic, soil-based crops but you can foliar feed hydroponic crops as well. Just start with a 25% dilution and gradually increase as the plants develop, but I never use more than a 50% dilution of the manufacturers recommendation for feed mix per gallon and use sparingly.
Miracle Grow works well for foliar feeding, but a lot of growers don’t like it due to its chemical content and Earth Juice is a good organic alternative, but any water soluble fertilizer suitable for cannabis will work. Mist daily and very lightly in the first two weeks of vegetative growth with a 25% strength per gallon solution and a ¼ teaspoon of dish soap liquid to help absorption. Choose a cheap unperfumed soap from your local store. The third week increase the mixture to 50% of the manufacturers recommendation per gallon, spray every 2 to 3 days. Watch the color of your leaves, this is the best guide – if you see any signs of nutrient burn leave the crop for a few days and decrease the strength of the mix. If the plants are not responding then increase the dose slightly.
When spraying during flowering try to avoid direct spray on big bud sites and reduce the frequency between intervals. If you see any evidence of nutrient burn cut back your application and reduce the strength. Its best not to foliar feed in the last 2 to 3 weeks before harvest.
As far as using the nutes in your reservoir, I would make a separate mix up and take out the root accelerator, no need to overkill that. Make a weak mix up first like diluted a quarter the recommended of each nutes per gallon and add quarter of a teaspoon of dish soap (use a cheap unperfumed one from your local store). Then spray every other day and watch the color of the plants – If they show no change and don’t get like get a nice strong green color you can gradually increase to half strength, but watch them closely. If you see any sign of nutrient burn (like copper coloring on the fan leaves) leave them a few days and dilute the mix back – I find each crop varies slightly due to strain and genetics etc. so the leaf color is the best guide for you to watch out for. Don’t over spray them and quit about 3 weeks before harvest. I try not to overspray the buds but if you do it early in the light cycle a light misting really brings them up.
In my opinion foliar feeding, is the best way to get the max out of the crop, the results show pretty much the next day as uptake is so quick.