A collection of useful charts, illustrations and so forth.

Light Efficiency Math
Here’s how to determine if purchasing an LED is right for you.

  1. Determine what you are already using in kilowatt hours (KHW) per month and multiply that by your cost per KWH to get your monthly cost. You can find all you need to know on your electric bill. Let’s look at an example:

    1000 watt HPS on 12 hours/day all month at 10¢ per KWH. 1000 watts = 1 KW x 12 x 30 = 360 KWH x $.10 = $36 per month to run your 1000 watt HPS lamp.

  2. Determine what your new LED will cost to run for the same period under the same conditions. For example, if you intend to replace your 1000 watt HPS with an LED unit rated at 600 watts, you would simply multiply your $36 by 60%, and you can see that you’d be spending $21.60 per month, which is a savings of $14.40 per month.
  3. Recall that sometimes you run your lamp 24 hours/day for the month. The percent savings is the same but the total saving jumps to $28.80 per month for that month.
  4. Figure on two months of 12-hour lighting and one month of 24-hour lighting per cycle. $14.40 + $14.40 + $28.80 = $57.60 per cycle.
  5. Four cycles per year gives you an annual energy cost savings of $230.40.

Because you no longer have to by a new HPS lamp every year, your Return On Investment (ROI) Period = Investment ÷ (Energy Savings + New Lamp Expense Savings).

To continue with our example: $1200 initial cost for your LED ÷ ($230.40 + $100 replacement lamp savings) = 3.6 years ROI Period.

That’s not the whole picture, though. That assumes a rapid plant life cycle and no change in product yield. Yield must be figured, too. For example, if the annual difference in yield is ($100) worth of bud, your ROI Period just went out to 5.2 years. You can see how this difference is significant and should be a factor into your decision. Therefore, our updated equation is:

Return On Investment (ROI) Period = Investment ÷ (Energy Savings + New Lamp Expense Savings +/- Difference in Yield) (because yield *could* increase, although it probably won’t).

A Damn Good Soil Formula
Structural mix:
– 35% coir.
– 25% chunky perlite.
– 25% peat.
– 10% compost.

Nutrient admixture:
– 40% composted manure.
– 25% topsoil (the real stuff—black, not the tan garbage that is all-too-often
– offered for sale).
– 10% dolomitic lime.
– 10% gypsum.
– 5% bone meal.
– 5% blood meal.
– 5% azomite or other source of trace minerals.

Stop with the structural mix if you wish to grow in “soilless” media. Using only the structural formula you will find it necessary to add your own nutrients. Be aware that the peat will tend to acidify the mix. If you wish to blend in all or most of your plant’s nutrition at the outset, combine the two mixes. A good approximate structural mix to nutrient admixture ratio is around 2:1.

My own product, Scientific Soils, is more sophisticated than the formula presented here, but that’s because I have access to computer controlled mixing machinery, highly advanced admixtures and the ability to run enormous volumes. This formula, comprised of ingredients you can find locally, will definitely get you to the finish line with your plants in good health, I promise.

Chart illustrating the availability of nutrients by media pH. You should be growing in the 5.7 to 6.8 range.

The three components of soil (sand, clay and silt) and their relative proportions with associated nomenclature. Note that soil composition has much to do with nutrient adsorption and availability.

Read more about soil chemistry over at Scientific Soils.

Photoperiod vs vegetative growth and days to flower from Robert Connell Clarke’s excellent Marijuana Botany: An Advanced Study: The Propagation and Breeding of Distinctive Cannabis. This settles the 24/0 vs 18/6 question fairly decisively. Note that when we speak of daylength, we really mean night length, as it is the period of darkness that is dispositive to the question of induction of flowering.

Know what is going to happen when you cross your favorite plants before you cross them by using this fantastic Punnett Square calculator! Sweet!