When to harvest to maximize THC

Everyone that's serious about growing has read Jeorge Cervantes' "Marijuana Horticulture" that tells you to harvest when the half amber half cloudy trichomes (or resin glands). There are also some very informative posts stickyed in the harvesting and processing area. The problem I see is most of these are based on smoke reports, and folklore, while they might be accurate, they are not the most scientific way of determining a harvest date. The good news is with medical marijuana we now have reputable scientific labs like Full Spectrum Labs that can test the THC, CBN, CBD, CBC and THCV in your medicine. Using High Performance Liquid Chromatography they can determine the % of all the different cannabionoids and their specific ratios. Why not use this technology to once and for all determine the best time to harvest?

I am going to take samples of this grow at different points of maturity to determine the time with the most potency. Each one of the samples will be from the same plant, on a top branch of similar elevation (same distance from the light) with a similar point of origin for the branch (all main branches). This will be a blind test in that the samples will be labeled with numbers only when submitted to full spectrum labs. The plants used are Barney's Farm Tangerine Dream and is supposed to have a 70 day flowering period with mind blowing THC levels of 25% and CBD of 1.8% (we'll see). If you would like more detailed information on how they are grown you can stop by my grow journal.

The three items I will be looking at to determine maturity is the:

1.) Days in flowering - for this experiment the plants were already showing sex before the lights were flipped to 12/12, so the day the lights were flipped will be day 1.

2.) Resin glands (more commonly called trichomes) - The number in a givin area will be counted and the total % of clear / cloudy / amber / brown will be recored.

3.) Stigma (more commonly called pistils) - These are the little white "hairs" that are fully erect when the plant is immature and then tend to pull back into the flower, curl and turn red/orange/brown as the plant reaches maturity.

4.) Seed Bracts (more commonly called Calyx) - These should swell at the end of flowering even in sensimillia flowers.

Each one of the flowers will be harvested at different points of maturity, dried under the same conditions and then submitted for testing. I will then cure the remaining to be submitted for cannabinoid levels at different stages of ageing.

Words of caution when using the above criteria -

Days of flowering - obviously this is going to be accurate to this plant only, different plants of the same type have different traits and therefore different maturity dates. Also to be noted breeders frequently give inaccurate flowering dates to help sell their seeds.

Resin glands - the time when these change can vary greatly and vary at different places on the plant (i.e. leaves vs flowers, outside of flowers vs inside of flowers, top of the plant vs bottom of the plant). They will also change due to stress on the plant (outdoor vs indoor, etc.).

Stigma - These can change from young are fertile to old and shriveled by more than age, pollination can trigger them, but so can rubbing against a surface like a leaf of the side of your grow box.

Calyx - Can vary greatly in size from strain to strain, so a swollen mature calyx on one type of marijuana may be much smaller than an immature calyx on another strain.

The flowers grown for this test will be Tangerine Dream with a breeders recommended harvest time of 70 days.

Samples will be taken at:
60 days (10/31/2011) -10
65 days (11/05/2011) -5
70 days (11/10/2011) 0
75 days (11/15/2011) +5
80 days (11/20/2011) +10
85 days (11/25/2011) +15

Each sample will be dried in my drying room that averages 30% RH and a temp of 65 deg F for 4 days and then will be trimmed, cured for a week and sent to Full Spectrum Labs for analysis. Here is a sample report:

Super Lemon Haze Report

The most potent sample (highest THC) will then have the medicine remain in jars to continue curing in a 65% dark space and sample will be submitted for testing on:

15 days of cure time
30 days of cure time
45 days of cure time
60 days of cure time
90 days of cure time
120 days of cure time

I am planning to edit this post as the results come in.

 

The grow is taking place right now, and the first chop will be taken on Halloween, some bad news is that Full Spectrum Labs is closing their doors with the Feds cracking down on everyone, the good news is there are two other labs in Colorado that are willing to work with me. I appreciate everyone stopping by and can't wait for the results.