Geeky Ganja Gardening

By: Soft Secrets, November 8, 2012

Growing marijuana is part art, and part science. In some ways, gardeners are very artistic; like a conductor in front of an orchestra they guide their plants from the start to harvest, listening for off notes signaling something isn't right. On the more scientific side, there ways to take the right sorts of notes to show how productive a garden, and a couple of pretty simple math bits than can be helpful.

Growing marijuana is part art, and part science. In some ways, gardeners are very artistic; like a conductor in front of an orchestra they guide their plants from the start to harvest, listening for off notes signaling something isn't right. On the more scientific side, there ways to take the right sorts of notes to show how productive a garden, and a couple of pretty simple math bits than can be helpful.

The simplest form of record keeping, is simply what varieties were grown. Which strains have you tried, and which are your favorites. When sitting down and making a wish list for the season, it's helpful to know which varieties you've tried. For instance I've had good luck in the past with Blue Widow, which is a White Widow and Blueberry cross, so I know when I'm looking around, to at least take a look at those crosses, even if they are named something else like Berry White, or Blueberry Widow. When looking for new varieties to try, you can try something similar to a known favorite, or intentionally try something completely different than you have in the past.

A somewhat more labor intensive and scientific bit to record, is how much was harvested. For example, 57 gram (2 ounces) of Purple Lady, or 170 grams (6 ounces) of Super Critical Haze.

Even if individual plants aren't tracked, calculating how much each plant averaged is simple, just divide the amount harvested by the number of plants. If two Super Critical Hazes produced 170 grams, then they averaged 85 grams (3 oz) apiece (170/2 plants).

This information can be used the next planting season when selecting how many seeds to plant. If the goal is to have 8 oz of smoke at harvest, and your garden tends to produce 2-3 oz per plant, then that would be 4 plants taken to harvest.

If using standard seeds, about half will be male so double that number to 8. I recommend planting a couple more as a safety net, as extra plants or harvest tends to be a easier problem to solve than not having enough.

Speaking of standard seeds, to figure out how many standard seeds you need to plant to get at least one female can be important when ordering from seed banks, it is all probability:

A single seed has two possibilities, either to be male of female. An approximate 50-50 chance of being female (the odds are actually better than that, but to keep it simple).

Two seeds have four combinations: MM,MF,FM, FF. Since 3 out of 4 of those combinations have a female plant in them, and 3 divided by 4 is .75, there is a 75% chance of one of them being female.

Three seeds have eight combinations: MMM, MMF, MFM, MFF, FMM, FMF, FFM, FFF. Since 7 out of the 8 combinations result in a female plant, and 7/8 is .875, or 87.5%.

Four seeds have 16 combinations, 15 of which include a female for 93.7%, Five seeds 31/32 for 96.8%, Six is 63/64 for 98.4%, Seven is 127/128 for 99.2%. Eight is 255/256 for 99.6%. Nine is 99.8%. Finally ten seeds will result in at least one female 1,023 times out of 1,024 for 99.9%. This is one reason why a standard breeder pack has at least ten seeds.

For expert level Gentle Readers, here is a tip: Gender and Mendelian genetic traits occur as one of two states, which make them very well suited for binary mathematics.

In a nutshell, about half the plants will be female, so sprout at least twice as many. To hedge against bad luck, plant a few more. To hedge against really bad luck, plant 4 times as many. If the universe hates you, plant ten times as many.

Outdoor gardens can compare growing season to growing season easily. Harvests can be compared year to year. Even climates which allow for a spring and fall harvest can be noted as simply as Spring 2012 and Fall 2012 with variety names and harvest quantities.

Indoors, seasons are a bit more arbitrary. Summer and Fall are set with lighting timers and other environmental controls. Short dark periods (six hours or less is common) mimic the long days of summer, and long dark periods (usually twelve hours or so) reproduce fall lighting. Indoor growing seasons may be as short as a 9 weeks, or or extended to several months depending on how long the plants are kept in growth, and how long the variety requires to flower.

To account for these differences, a time factor can be included into the calculations. Grams per day (GPD) allows for plants of different growing periods to be compared. Take the planting date and subtract the harvest date to find the number of days between. If plants were started 5-23-2012, and harvested 9-29-2012 the season would be 130 days (9 days left in May, 30 days in June, 31 in July, 31 in August, and 29 days into September).

If the Purple Lady example were used, then it's average weight of 57 grams per plant could be divided by the 130 days it took to grow them, to show a GPD of .438 (57 grams/ 130 days = .438 grams per day).

In the Super Critical Haze example, if it instead didn't ripen until sixteen days later on October 5th. Then the 85 grams would have taken 146 days. That would give a GPD of .582 (85 grams/ 146 days = .582 grams per day).

A common practice in indoor gardening is to introduce plants into the flower room at the rate of few per week or two, so that the harvest is spread out over a longer period of time. This is especially common in personal grows, where it can produce small amounts for consumption every couple of weeks. By tracking individual plants, they can be compared against an overall average and in that way performance can be tracked quantitatively.

In an outdoor garden, day efficiency concerns have more to do with working around the seasons. Having plants with enough growth before flowering starts, getting a short enough flowering strain to harvest before the weather turns foul, etc. Indoors however, lighting generally causes a higher operating expense, and each day of electricity is a cost. Indoors, GPD is a valuable tool in comparing the efficiency of the grow (although art is still required to judge the quality of the flavor and effects). Production isn't the only factor to consider, preference and quality should also be taken in to account. If the flavor of a poor producer is preferred, then more plants may be needed to meet harvest goals.

Although the finer points of rating a plant are largely artistic and subjective, responses don't have to be. To set up a simple double blind test, first take opaque identical containers for each variety to be tested. Write the name of the variety on a piece of paper, and seal in an unmarked envelope. Put the sealed envelope into the container, with the matching cleaned weed. Either mix up the containers until you know longer know which is which, or have a friend do it for you. Mark each container with an arbitrary number or a letter. While smoking from each, keep track of reactions from the weed from each container. Questions should include “Which do you like the best: A, B, or Can't Tell?” and “Describe the flavor of each”. Record and tally the results from each participating tester. Since the envelopes contain the real identity of each container, after the tests have been completed, the envelopes can be opened in turn, and associated with their letter.

Why go to the trouble of a blind (or in this case double blind) test? Because humans are very suggestible, and some variety names sound better than others. Weed labeled “top shelf” tends to influence the reactions of the people that smoke it. Relabeling the smoke into something boring helps minimize the influence. If possible, the person handing out the weed shouldn't know either, as their behavior can have an influence as well, which is why the envelopes and identical containers are important.

The GPD for the whole garden or each individual plant can be calculated and compared

Individual plants with high production rates are often particularly good candidates for breeding. Although production should not be the only factor in selecting parent plants, as long as there is not a reduction in quality, quantity is often considered a desirable trait.

Once the base rate of production is calculated, it can be used in conjunction with other pieces of data for a variety of useful purposes: nutrients, growing medias, and other expenses can be taken into account.

A little math comes in handy when making nutrient selections as well. The NPK listing on nutrients indicate the percentage by weight of Nitrogen (N), Phosphorous (P) and Potassium (K) (to be picky, the P actually indicates how much equivalent phosphorous pentoxide, and the K how much equivalent potassium oxide, but most of the time that makes little to no difference).

What this means, is that a nutrient solution made with a fertilizer with a value of 5-0-0 that is applied at 15 ml a liter should have the same nitrogen content as one with a value of 15-0-0 applied at 5 ml per liter. It is the final amount of nitrogen in the nutrient solution that counts, not how concentrated the original nutrient was.

When deciding which to use in the future, it will come down to whether nutrient B is worth an additional twenty cents per treated liter. To find out for sure, test a few plants using each nutrient. Record the nutrient expenses used to grow both sets, and calculate the GPDs at harvest. Not only should the more expensive nutrient produce more, but enough more to cover the additional expense in order to be worthwhile.

The same can be calculated for electricity and lighting costs. An examination of your electric bill should tell you at what rate you are charged for electricity, and that can be used to calculate how much your cost is per day to run the lights. Each additional 1000 watt light adds 1 kilowatt hour in electrical expense, not to mention the cost of the equipment and bulb replacements. If a change in gardening techniques is shown to improve then consider keeping the change. If it doesn't, consider discarding it and returning to previous methods. Improvements to the garden should result in documentable improvements in production or quality to be cost effective.

Media choices can be another concern, single use media is good for hygiene, but it is a larger recurring expense than reusing media. To find out how much, take the total expense for the garden during the grow, divide by the number of days in the grow, and compare to the GDP. Obviously the expense rate should be less than the value of the harvest, or serious changes are in order.

While only the most avid of gardening geeks may calculate every plant in the garden, this type of information can be valuable when comparing successes, and determining the value of a change in the garden. By comparing production rates before and after a change, improvement can be compared to cost, and future plans fine tuned accordingly. The benefits of home grown vegetables include peace of mind, and knowledge of the conditions that the food was grown under, but that doesn't mean that they can't be grown with a nod to efficiency and expense concerns as well.

Peace, love and puka shells,

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