Growing basics: your first grow

Want to grow yourself for the first time? Great – here is the overview: indoor or outdoor, light, substrate, nutrients, watering, the phases of a plant and the mistakes almost everyone makes at the start. Where there are studies, I link them. Where there is (so far) only practical knowledge, I say so.

Indoor or outdoor?

Rows without a source are practical considerations, not study results.

Light

Cannabis is a short-day plant: long days promote growth, short days trigger flowering.^[2] Indoors, people therefore usually work in two phases. In one study, for example, plants first grew under 18 hours of light / 6 hours of darkness and then flowered under 12 / 12 hours.^[3] With autoflowers the switch is not necessary.^[4]

Hempey’s tip

When choosing a lamp, wattage alone is not what counts, but how much light actually reaches the plants. This is measured as PPFD (in µmol per m² per second) – the studies refer to this value too.^[3]

📚 Light & Spectrum: What Do Lumens Mean, Why Do Indoor Lamps Use Blue/Red/Violet Instead of Sunlight & Does Under-Canopy Light Really Work?

Medium: soil, coco & co.

Roughly, there are three routes (practical knowledge): soil (most forgiving of mistakes, sometimes already contains nutrients), coco coir (airy, but needs targeted feeding) and hydroponics (roots in nutrient solution, lots of control, little buffer). Flo’s practical substrate mix: I blend my own airy medium from quality soil, worm castings (vermicompost), quartz sand and Seramis clay granules, enriched with Living Soil. Seramis stores moisture and nutrients without waterlogging, sand ensures lasting drainage and structure, and worm castings + Living Soil maintain an active soil microbiome.

A note from research: fungal communities in unpasteurised coco coir have been described as a possible source of mould on cannabis plants.^[6]

Nutrients

The three main nutrients are nitrogen (N), phosphorus (P) and potassium (K). One hydroponic study is interesting: flower yield rose with nitrogen and phosphorus only up to a calculated optimum – more did not help; it did not respond to potassium at all within the range tested.^[5]

Hempey’s fact check

“The more the better” is not true for fertiliser. Better to start cautiously and stick to the instructions on the pack. Specific values from hydro studies cannot simply be transferred to soil.^[5]

Watering

Root rots are among the most important diseases in cannabis growing^[7]: fungi and oomycetes such as Fusarium and Pythium caused brown roots, stunted growth, yellowing and sometimes plant death in studies.^[6] For prevention, experts name hygiene, good irrigation management and control of the room climate, among other things.^[7]

Practical knowledge (not studied): many growers only water once the top layer of the substrate has dried a little, and make sure excess water can drain away. Flo’s watering & feeding routine: I hand-water daily shortly after the lights turn on – first, because plants open their stomata at the start of the light period when transpiration demand peaks, and second, as a deliberate daily inspection walk: automatic irrigation is convenient, but hand-watering every morning lets you spot the tiniest change in leaves, shoots and soil immediately! Following my motto “Understand nature, then copy nature”, I feed 100% biologically with worm tea (vermicompost liquid) and homemade fermented nettle manure (Brennnesseljauche) (rich in plant-available N, K, iron and silica) alongside strong continuous intake, exhaust and circulation airflow.

The phases of a grow

1. Germination: the seed opens and the radicle appears. Flo’s practical tip: For outdoor and autoflower grows, I germinate seeds directly in soil or Jiffy pellets (avoiding transplant shock to the taproot). For indoor photoperiod strains, I briefly pre-soak them in water and then germinate them in a moist cloth/paper towel between two plates or inside a closed lidded box in a warm spot (22–25 °C) until the root tip appears – see Seed Storage & Germination.
2. Seedling: the first leaves form; the plant is sensitive now.
3. Vegetative phase: under long days the plant grows taller and wider.^[2]
4. Flowering: under short days (or by themselves in autoflowers) the inflorescences form.^[2][4] With regular seeds, it becomes clear by now at the latest which plants are male.
5. Harvest, drying & curing: I determine peak harvest timing with a 60× loupe directly on the calyx trichomes (~75–85% milky, 15–25% amber – see Trichome Guide), followed by slow dark drying at 18–20 °C and 55–60% RH with gentle airflow (10–14 days) and curing in airtight glass jars at 58–62% RH to preserve volatile terpenes.

How long each phase lasts depends heavily on strain, seed type and conditions. In botanical literature (Clarke & Merlin 2013; McPartland & Small 2020), flowering duration ranges from 7–9 weeks in compact mountain BLD/Indica lines and 9–11 weeks in modern hybrids to 11–16+ weeks in equatorial NLD/Sativa landraces.^[9]

Typical beginner mistakes

You will find more about nutrient deficiencies, pests and fungal diseases in the category Deficiencies & pests.

My experience

Flo’s Practical Principles: “Understand nature, then copy nature”

For me, growing is all about the living plant and its botany rather than chasing a high. Three habits make the biggest difference in my garden:

• Hand-watering daily right after lights-on: As soon as the lamps switch on, leaf stomata open and transpiration begins. Watering by hand every morning instead of relying on blind automation forces me to inspect every single plant closely each day.
• Custom substrate & organic feeding: I mix soil, worm castings, sand and Seramis clay granules enriched with Living Soil, and feed biologically with worm tea and homemade fermented nettle manure (Brennnesseljauche) under strong intake, exhaust and canopy airflow.
• KCanG compliance (§ 9 & § 10 KCanG): Living as three adults in our multi-generational home, we strictly respect the 3-plant-per-adult limit and keep our grow room locked against third-party access.

Note: personal experiences are subjective and are not a recommendation.