Short-Day Plant Lifecycle
As a short-day plant matures, its environmental and nutrient requirements change. Different conditions and nutrients are needed at each stage of growth, and special care must be taken with light exposure since it triggers the transition from vegetative growth to flowering. Regardless of whether plants are raised in soil or in hydroponics, their maturity based needs are much the same.
Germinating Short-Day Plants
Short-day plant seeds germinate within 3-7 days if they are viable. There are many options for seed germination, but using simple jiffy pots or disposable cups of soil is sufficient. A germination mat can be used to keep the growth medium warm and encourage germination. During germination, cool (blue) fluorescent lighting should be used with an 18-hour exposure period. If sown outdoors, seeds planted in May should be ready to harvest in September. Once seedlings have established a good root system they can be transferred to larger pots, or to hydroponic systems.
Cloning Short-Day Plants
To clone a mother plant, a healthy plant in the vegetative growth stage is selected. A 6-10 cm segment containing at least two nodes is cut away at a 45° angle. Cuttings can be taken from the lower branches of the mother plant. The cutting should be immediately placed in distilled water, then the bottom 2 cm of the cutting can be dipped in rooting hormone. Cuttings can be rooted in small pots containing a 1:1 mix of coco coir and potting mix and kept under 18-24 hours of light at 27°C and 95-100% humidity for 1-1½ months. If cuttings are grown in plugs, they will need to be transplanted sooner. At least one node on the clonal cutting should be covered by the soil or germination plug. Roots start to form after 2-3 weeks. Plants can be transferred to hydroponic systems or larger pots when root and biomass growth is sufficient (4-6 weeks with rooting plugs).
In between germination and vegetative growth, the plants undergo a 2-3 month juvenile stage (may be shortened in accelerated growth environments). During this stage, plants grow towards a light source. 18 hours of exposure to cool (blue) fluorescent light is sufficient for younger plants. As plants grow and become large enough for transplant to a larger pot, they can be put under a full spectrum grow light for 18 hours per day. Juvenile plants thrive in high humidity around 75-80% that can be reduced once plants are well rooted and enter full vegetative growth. Plants in this stage should also have their leaves sprayed with water regularly.
When plants are in the vegetative growth stage they increase the production of foliar biomass (leaves, branches). Experienced growers may be able to determine plant gender, which is also detectable with laboratory testing. Growers able to identify high-quality female plants can keep selected plants in the vegetative growth stage to take clonal cuttings. At least 18 hours of a full-spectrum light is needed to maintain the vegetative phase. Plants should be kept in 55-70% relative humidity at 25-30°C.
A short-day plant flowers when it is exposed to a short day length, signaled by 12 hours of light exposure and 12 hours of darkness. Within 2 weeks flowering will begin with males flowering just before the females. Gender at this stage is apparent, and if male plants are not removed female plants can be wind-pollinated when their flowers ripen. For breeding, pollen from male plants can be collected and stored frozen for up to 3 years.
Temperature and humidity conditions can be maintained as they were through the vegetative stage (humidity may also be lowered to ~50-60% if desired), but a nutrient solution or fertilizer specific to the flowering stage should be used. After approximately 8 weeks flowers begin senescence. Mature buds change in color to an orange or brown shade when they are ripe and ready for harvest.
At the end of the plant's lifecycle, male plants will die just prior to seed ripening in female plants. Seeds ripen within 3-10 weeks. Female plants can produce up to a kilogram of seeds.