Growing cannabis from seed offers complete control over a plant’s life cycle, from genetics to harvest. This guide focuses on horticultural practices specific to New Zealand’s unique climatic conditions. Readers must comply with all current local regulations, as cultivation for personal use without a license remains illegal under New Zealand law.
Seed Selection and Germination
Choosing the right genetics involves selecting between photoperiod and autoflowering strains. Photoperiod plants flower only when daylight hours decrease, allowing growers to control the vegetative phase indoors using long light cycles. This control enables larger plants and higher yields, but requires a longer total growing time of four to six months.
Autoflowering seeds are simpler for beginners, automatically switching to the flowering phase after three to four weeks, regardless of the light cycle. These varieties are smaller and faster, moving from seed to harvest in eight to twelve weeks, making them ideal for quick outdoor seasons. Feminized seeds are essential for most growers as they ensure nearly all plants are female, producing resin-rich flowers and eliminating the need to remove male plants.
Successful germination requires moisture and warmth, with the optimal temperature range being 21–27°C (70–80°F). A common method is the paper towel technique, where seeds are placed between moist paper towels inside a sealed container to maintain high humidity. Alternatively, direct soil planting involves placing the seed 1 to 1.5 cm deep in a small starter pot of moist soil. Once the seed sprouts a small white taproot, it must be gently transferred to its initial growing medium, handling the delicate root as little as possible.
Establishing the Growth Environment
Outdoor cultivation in New Zealand is dictated by the growing season, running from late spring to autumn to avoid frost. North Island growers can safely transplant seedlings outdoors around Labour Weekend (late October). Cooler South Island regions should wait until early November or later. Photoperiod plants naturally begin to flower as days shorten around mid-February, leading to a harvest window from late March to late April.
Indoor growing allows for year-round cultivation and complete environmental control, which is necessary for photoperiod plants to maintain their vegetative state. The medium choice is typically soil or coco coir; soil buffers nutrients for beginners, while coco coir offers faster growth but requires precise nutrient management. Plants should start in small containers, such as 1-liter pots, and be gradually transplanted into larger pots, often finishing in 10-liter or larger containers to support a strong root system.
For indoor seedlings, low-wattage LED or fluorescent lights should be positioned 30–60 cm (12–24 inches) above the canopy to prevent scorching. As the plant enters the vegetative phase, light intensity is increased, and the distance is reduced to 30–45 cm (12–18 inches) for medium-wattage LED systems. Maintaining a warm root zone is important, as cold temperatures can stunt growth; the ideal air temperature range is 21–26°C (70–79°F).
Vegetative and Flowering Care
The vegetative phase requires nutrients high in Nitrogen (N) to fuel leaf and stem growth, with an ideal NPK ratio around 3:1:2 or 3:1:1. Nitrogen is essential for chlorophyll production and cell division, building the plant’s structure to support later flower weight. The medium should be allowed to partially dry out between waterings to ensure the roots receive oxygen and prevent suffocation.
Growers employ training methods during this phase to manage height and maximize light exposure to lower branches. Low Stress Training (LST) involves gently bending and tying down the main stem and branches to create a flat, even canopy, promoting uniform development of bud sites. High Stress Training (HST) techniques include topping, which involves cleanly cutting the main growth tip to force the plant to develop two new dominant stems. Fimming, a less precise cut of about 75% of the growth tip, can produce up to four new main shoots, encouraging a bushier structure.
For photoperiod plants indoors, the flowering phase is triggered by switching the light cycle to 12 hours of uninterrupted darkness and 12 hours of light. Outdoors, this occurs naturally as the nighttime period lengthens. During flowering, the nutrient ratio must shift dramatically to lower Nitrogen and higher Phosphorus (P) and Potassium (K) concentrations, such as 1:3:2, to support bud development. Phosphorus aids energy transfer and flower formation, while Potassium enhances overall flower quality and density.
Sex identification is necessary when using regular seeds and must be performed before male plants release pollen, which ruins the female crop by creating seeds. Male pre-flowers appear at the nodes as small, round pollen sacs, typically emerging earlier than females. Female pre-flowers are teardrop-shaped calyxes with one or two wispy white hairs (pistils) emerging from them.
A significant challenge in New Zealand’s humid climate is mold, particularly Botrytis cinerea (bud rot), which thrives in stagnant air and high humidity. Prevention is achieved through excellent air circulation from oscillating fans, preventing humid microclimates within dense foliage. During flowering, humidity should be kept below 50%, ideally dropping to 35–45% in the final weeks before harvest. Outdoor growers should ensure proper plant spacing for airflow and select mold-resistant strains.
Harvesting and Post-Processing
Determining the precise moment for harvest relies on observing the microscopic, mushroom-shaped trichomes on the buds, which contain cannabinoids and terpenes. A jeweler’s loupe or digital microscope is needed to accurately monitor the trichome head color. Immature trichomes appear clear, signifying low potency, while a milky or cloudy appearance indicates peak THC production and a more uplifting effect.
The optimal harvest window for a balanced effect is when 70–80% of the trichomes are milky and 20–30% have turned amber. Amber trichomes signify that THC is degrading into other compounds, leading to a more sedative effect. Once the desired ratio is reached, the plant is harvested by cutting down the branches or the entire plant.
Initial processing involves trimming away the large fan leaves and then removing the smaller sugar leaves, which can be done before or after drying. The branches should then be hung upside down in a dark, well-ventilated space with temperatures between 15–21°C (60–70°F) and a relative humidity of 45–55%. This slow drying process takes seven to fourteen days, ensuring moisture evaporates slowly to preserve flavor and aroma.
The final stage is curing, which maximizes quality and ensures a smooth smoke. Once the small stems snap cleanly, the dried buds are placed into airtight glass jars, filling them about three-quarters full. For the first week, the jars are “burped” by opening them for a few minutes several times daily to release trapped moisture and prevent mold. This curing process continues for several weeks to months, improving the final product’s complexity and potency.