Short answer
Feed an autoflower lightly early and steadily later: about EC 0.4–0.6 mS/cm for the first two weeks (or water only in good soil), 0.8–1.2 in weeks 3–4, and 1.2–1.8 in flower. Start at a quarter to half the label rate and feed right through to harvest. Grower practice, house-endorsed.
Why
An auto can't catch up. It flowers by age, so a hungry or burnt plant in week 3 builds a smaller frame and flowers on it anyway. Both overfeeding and underfeeding cost yield.
Nutrient rate matters in veg. In coir-based media, cannabis grew best at a moderate fertiliser rate, with poorer growth above and below it [1].
Nitrogen is the one to taper, not everything. Lower nitrogen late can raise cannabinoid and terpene percentage while lowering total yield [2]. The GenetixBay approach is to cut nitrogen back near the finish while keeping P, K, Ca, Mg, S and the micros fed.
Flushing doesn't help. In controlled work, withholding fertiliser before harvest tended to lower dry mass and cannabinoid yield [3]. It starves the plant during its heaviest weeks.
The numbers
| Week from sprouting |
Feed EC (mS/cm, coco) |
ppm500 |
ppm700 |
| 1 |
0–0.4 |
0–200 |
0–280 |
| 2 |
0.4–0.6 |
200–300 |
280–420 |
| 3 |
0.6–1.0 |
300–500 |
420–700 |
| 4 |
0.8–1.2 |
400–600 |
560–840 |
| 5 |
1.0–1.4 |
500–700 |
700–980 |
| 6–7 |
1.2–1.6 |
600–800 |
840–1,120 |
| 8–harvest |
1.4–1.8 |
700–900 |
980–1,260 |
Soil: often water only until week 3, then feed at about half label rate. pH 6.2–6.8 in soil, 5.8–6.2 in coco.
What to do
- Start at a quarter to half label strength; raise it as the plant grows.
- Check runoff EC weekly; if it climbs well above your input, cut back.
- Read the leaf tips: slight burnt tips mean back off, pale lower leaves mean feed more.
- Keep feeding at stage strength to the chop. Taper only nitrogen, if you mix single salts.
Common mistakes
- Full-strength chart doses from week one.
- Starving the plant "because autos are small".
- Flushing for the last two weeks.
- Blaming nutrients before checking pH and overwatering.
A day-neutral cannabis plant that starts flowering by age, usually a few weeks after germination, regardless of light schedule; the trait is mainly recessive.EC (electrical conductivity) measures how well a solution conducts electricity, a proxy for total dissolved salts; growers read it in mS/cm to gauge nutrient strength.mS/cm (millisiemens per centimetre) is the standard unit of EC for nutrient solutions; 1 mS/cm equals 1 dS/m and 1,000 µS/cm.Nutrient toxicity is damage from an excess of an element in the plant, either directly or by blocking uptake of others; boron, manganese, copper and chloride are common culprits.A cannabinoid is any compound that binds the body's cannabinoid receptors or shares the typical cannabis terpenophenolic structure; the plant-made ones are phytocannabinoids such as THCA and CBDA.Terpenes are volatile hydrocarbon compounds built from five-carbon isoprene units; in cannabis they are made in the trichome heads and are a major part of aroma and flavour.A micronutrient is an essential element plants need only in trace amounts, below a few mg/L: iron, manganese, zinc, copper, boron, molybdenum, chlorine and nickel.Feeding only plain water for days or weeks before harvest to "clean" the plant; GenetixBay rates it a Myth that harms yield, unlike a root-zone salt flush.Germination is the stage where a viable seed absorbs water, splits its shell and pushes out a root (radicle), usually within 1-7 days at 20-30 °C.Coco coir is a growing medium made from processed coconut husk, prized for holding water and air at once; it binds calcium and magnesium unless buffered.ppm500 is the TDS scale that converts EC to ppm with a factor of 0.5 (based on sodium chloride), so 1.0 mS/cm reads 500 ppm.ppm700 is the TDS scale that converts EC to ppm with a factor of 0.7 (the 442 natural-water standard), so 1.0 mS/cm reads 700 ppm.pH measures how acidic or alkaline a solution is on a 0–14 scale; in growing it controls nutrient uptake, with soil best near 6.0–7.0 and hydro 5.5–6.5.Runoff is the water or nutrient solution that drains out of the bottom of a container after irrigation; growers test it to see what is happening in the root zone.Nutrient burn is browning and crisping of leaf tips, then margins, caused by a root-zone salt concentration (EC) higher than the plant can handle.Overwatering is watering so often that the medium stays saturated, starving roots of oxygen, which causes drooping, slow growth and root disease.
