The Cannabis Breeder's Bible (28 page)

Feminized seeds perform on the foundation that there is a genetic predisposition for the seed to produce only females because of the unique treatment that the XX female parent plant was subjected to. We discussed this treatment of an XX female in chapter 2 and you may want to refer back to that material again.

Under optimal growing conditions, which all good growers should have, the feminized seeds will produce only females. Feminized seeds appear to produce only females in growing conditions that are well maintained. In growing environments that are less than optimal, or in situations where the plants are stressed, males and hermaphrodites tend to show up in populations. This shows that sexual expression is not governed by the plant’s genes alone and that the environment plays an active roll in the final expression of the plant’s gender.

Seed banks cannot be responsible for bad female to male ratios. Can they be held responsible for feminized seeds turning male? Since this is very much dependent on the growing environment, the answer is no, they should not be held responsible.
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You may be interested to know that the breeder/seed bank Dutch Passion released a statement of male and female ratios. This was because Dutch Passion were among the first breeders to release feminized seeds onto the market. Here is what they had to say:

Feminized Cannabis Seeds Courtesy of Dutch Passion

In November 1998 we introduced our “Female Cannabis Seed.” We did this after our own experiments showed that from female seed, we acquired almost 100 % female offspring.

In the meantime we are six months further on. We have received a lot of feedback from our customers. The reactions are mostly positive, from clients who have successfully produced almost 100 % female offspring. However there have been reactions from customers who found a few hermaphrodites or males plants. Apparently environmental influences affect the sex of the female seeds as well. Because of the fact that female seeds do not grow into female plants under all circumstances, we changed the name from “Female Cannabis Seeds” to “Feminized Cannabis Seeds.”

From literature and from our own findings it appears that the growth of a male or a female plant from seed, except for the predisposition in the gender chromosomes, also depends on various environmental factors. Not only the origination of entirely male or female plants is partly affected by these environmental factors, the number of male and female flowers on a hermaphrodite plant is affected as well. The environmental factors that influence the sex of the plant (or the flower in the case of hermaphrodites), are, among other things:

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the quantity of nitrogen and potassium of the seedbed

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humidity and moistness of the seedbed

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level of temperatures

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color of the light used

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length of daylight

Stress, any form of stress, causes more male individuals to originate from seed.

Even the taking of cuttings from female plants may produce male or hermaphrodite cuttings.

To optimize the result, changes in one or more of the above-mentioned environmental factors for a certain period during growth, may be applied. During this time these environmental factors will deviate from the standard growing system for maximum harvest and quality, as described in nursery literature. The desired change(s) in the environmental factor(s) are started from the moment that the seedling has three pairs of real leaves (not counting the seed-lobes). This is the moment that male and/or female predisposition in florescence is being formed. After approximately two weeks the standard growing system can be reconverted to.

Of the five above-mentioned environmental factors the first three are the most practical:

1.
Level of nitrogen and potassium of the seedbed: a heightening of the standard level of nitrogen makes for more female plants originating from the seeds. A lowering of the nitrogen level shows more male plants. A heightening of the level of potassium tends to show more male plants, while a lowering of the potassium level shows more female plants. A combination of a higher nitrogen level for the period of a week or two and a lowering of the potassium level is recommended.

2.
Humidity and moistness of the seedbed: a higher humidity makes for an increase in the number of female plants from seed, a lowering for an increase in male plants. The same is valid for the moistness of the seedbed.

3.
Level of temperatures: lower temperatures make for a larger number of female plants, higher temperatures for more male plants.

4.
Color of the light used: more blue light makes for female plants from seed, more red light makes for more male plants.

5.
Length of daylight: few hours of daylight (e.g., 14 hours) makes for more female individuals, a long day (e.g., 18 hours) makes for more male plants.

Most good growers choose standard seeds over feminized seeds for a number of reasons. Feminized seeds are expensive and are more likely to produce hermaphrodites as a result of stress than do standard seeds that are stressed. Since the hermaphrodite condition is not considered advantageous by growers who wish to produce a sinsemilla crop they will generally stick with standard seeds as opposed to feminized seeds, which have a propensity to herm if they go through a little stress.

With standard seeds the hermaphrodite condition is still realizable through stress but is very strain-dependant. There are two main very stressful conditions which promote the hermaphrodite trait in both standard and feminized seeds: first, an irregular flowering photoperiod and second, heat stress.

Heat Stress, obvious with the non-uniform bleaching and curling of the upper leaves.

During the later stages of the vegetative phase of growth the cannabis plants seem to have more of a predisposition to the manipulation of their sexual expression during flowering. This period occurs during sexual maturity, which is about a week or two before initial calyx development begins. Plants that are subjected to stress before calyx development tend to produce more males and hermaphrodites when they flower. Plants that are not subjected to stress before and during calyx development generally show more females in optimal growing conditions.

This stage of growth should be very interesting to growers who wish to try and promote more females than males in their gardens, although plant stress after sexual maturity can cause hermaphrodites to show.

Sinsemilla
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crops may also show hermaphrodites during the final few weeks or days of flowering before their harvest time. This appears to be a natural condition with some strains and generally the hermaphrodites are few and the pollen is sometimes nonviable.

It appears that the critical time for sexual expression occurs shortly before initial calyx development. Some growers like to force flower their plants before calyx development and this type of force flowering by photoperiod manipulation is prone to creating more males than females and even some hermaphrodites. This appears to be a very important area of plant growth in dictating the expression of the plant’s sex. Plant populations that are free from stress before calyx development will show an increase in females.

Keeping plants free of stress will help increase your chances of producing females and some slightly stressful situations that are part of any good propagation program may influence sexual expression. Transplants, topping and pruning are all important parts of cultivation but can be stressful and may influence the final sexual expression of the plant. On the other side, pest attacks, fungi attacks, mold problems, pH fluctuations, underwatering, overwatering, small pots, nutrient deficiencies and inappropriate soil mixtures can also have an adverse effect on sexual expression.

Some bottle-sized colas getting thick. Photograph by Alan.

Here are some ways we can improve on Dutch Passions’ methods for promoting females.

Nutrients

By using the right nutrients in the right ratios we can influence sexual expression. Nutrient formulas that are equal in N, P and K will help promote more females, but if the N levels decrease and P levels increase during vegetative growth we may see more males than females. It is wiser to have more N than P and K amounts for this reason and this ratio is quite suitable for cannabis plants in vegetative growth anyway.This is especially important during the phase before initial calyx development occurs.

Watering

Before initial calyx development you should ensure that your plants are properly watered and are neither over- nor underwatered. Allowing the soil to completely dry out is never a good idea. Careful watering will help improve your chances of developing females.

Humidity

Higher humidity levels encourage cannabis-related diseases like mold and fungi. The best way to help solve these problems is to reduce the humidity levels in your growing environment. However an rH of 70 is considered a very good humidity level to promote females in the population. Cannabis disease thrives in these rH levels and so extra care must be paid to your plants in order to ensure that mold and fungi do not form. Mold and fungi will only stress your plants and this will lead to less females.

Temperatures and the Photoperiod

There are two main photoperiods that the grower can use in the vegetative phase of the plant’s growth. These are 24/0 and 18/6. The 24/0 photoperiod should create a consistent temperature level in the grow room, whereas the 18/6 will not because there are 6 hours of darkness and during this period the heat from the grow bulb will not contribute to the temperature of the grow room. Special attention must be paid to preventing your grow room from getting too cold during this period of darkness if you use the 18/6 vegetative photoperiod.

To promote female growth, temperatures before calyx development should be between 65 and 75 degrees. Going below 65 to 55 will only promote average male to female ratios. Below 55 and you will stunt growth considerably, and cause more males and hermaphrodites to develop. Between 75 and 85 you will promote average amounts of male to female ratios. Again, this is very subjective but growers who stick between 65 and 75 degrees tend to see more females. Some strains can grow well in temperatures above 85, especially if they are of the equatorial variety.

Lighting

If you use MH (metal halide) lights in vegetative growth and HPS (high pressure sodium) in flowering you will see more females. Most growers who can only afford one light choose a HPS because it is more suitable for flowering than the MH, but MH users see more females after using this bulb type during vegetative growth.

This is a very good reason to use both MH and HPS lights to grow cannabis.

All the indications are that the plant chooses its sexual phenotypical expression just before pre-flowering, at about two to three weeks into vegetative growth. After pre-flowering some females may be forced to produce male flowers if exposed to stress factors, like heat or photoperiod manipulation, but if the plant is not stressed then the gender will remain consistent until harvest. However it must also be noted that this is very genetic dependent and not all strains of cannabis are environmentally influenced with regard to sex or more specifically not all of the offspring of a cross may be environmentally influenced to produce a certain sexual type. There may well be some members of a population who will display the sex set in the seed because of another gene that negates environmental influences on the sexual expression of the plant. Some strains or hybrids may be more prone to environmentally influenced phenotype gender expressions than others. However any good gardener will tell you that a good healthy grow room coupled with good genetics and an experienced green thumb will produce more females than males. You have to get all the above right before you start seeing the benefits. However, we should look at how sex is set in the seed a bit more.