# How should I feed autoflowers?

> Feed autoflowers lighter than photoperiods but don't starve them: plain water or about EC 0.4–0.6 mS/cm for the first two weeks, 0.8–1.2 in weeks 3–4 and 1.2–1.8 in flower, starting at a quarter to half the label rate. Quality bagged soil often needs water only for 2–3 weeks. Feed through to harvest; don't flush. Hunger in week 3 costs yield an auto can't recover.

- Canonical: https://genetixbay.com/knowledge/answers/feeding-autoflowers.html
- Topic: Basics · Type: How-to
- Evidence: Grower practice · Status: Draft: awaiting expert review
- Full article: [Photoperiod vs autoflower, and how autoflowering is inherited](https://genetixbay.com/knowledge/basics/photoperiod-vs-autoflower.md)
- Also asked as: Do autoflowers need less nutrients? | Autoflower feeding schedule | How much nutrients for autos? | What EC should I feed my autoflower?
- Updated: 2026-10-31 · Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay Knowledge Base (genetixbay.com/knowledge)"

## Short answer

Feed an [autoflower](https://genetixbay.com/knowledge/glossary/autoflower.md) lightly early and steadily later: about [EC](https://genetixbay.com/knowledge/glossary/ec.md) 0.4–0.6 [mS/cm](https://genetixbay.com/knowledge/glossary/ms-cm.md) 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](https://genetixbay.com/knowledge/glossary/nutrient-toxicity.md) 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](https://genetixbay.com/knowledge/glossary/cannabinoid.md) and [terpene](https://genetixbay.com/knowledge/glossary/terpene.md) 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](https://genetixbay.com/knowledge/glossary/micronutrient.md) fed.

[Flushing](https://genetixbay.com/knowledge/glossary/flushing.md) 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](https://genetixbay.com/knowledge/glossary/germination.md) | Feed EC (mS/cm, [coco](https://genetixbay.com/knowledge/glossary/coco-coir.md)) | [ppm500](https://genetixbay.com/knowledge/glossary/ppm500.md) | [ppm700](https://genetixbay.com/knowledge/glossary/ppm700.md) |
|---|---|---|---|
| 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](https://genetixbay.com/knowledge/glossary/ph.md) 6.2–6.8 in soil, 5.8–6.2 in coco.

## What to do

1. Start at a quarter to half label strength; raise it as the plant grows.
2. Check [runoff](https://genetixbay.com/knowledge/glossary/runoff.md) EC weekly; if it climbs well above your input, cut back.
3. Read the leaf tips: slight [burnt tips](https://genetixbay.com/knowledge/glossary/nutrient-burn.md) mean back off, pale lower leaves mean feed more.
4. 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](https://genetixbay.com/knowledge/glossary/overwatering.md).

## Related

- Full article: [Photoperiod vs autoflower](https://genetixbay.com/knowledge/basics/photoperiod-vs-autoflower.md)
- Answers: [when to stop feeding](https://genetixbay.com/knowledge/answers/when-to-stop-feeding-before-harvest.md) · [full-strength feeding charts](https://genetixbay.com/knowledge/answers/full-strength-feeding-chart.md) · [feed every watering?](https://genetixbay.com/knowledge/answers/feed-every-watering.md)
- Articles: [the flush debate](https://genetixbay.com/knowledge/harvest-cure/flush-debate.md) · [feeding basics](https://genetixbay.com/knowledge/guides/feeding-basics.md)
- Terms: [nitrogen taper](https://genetixbay.com/knowledge/glossary/nitrogen-taper.md) · [EC](https://genetixbay.com/knowledge/glossary/ec.md)

## Follow-up questions

**Do autoflowers need less nutrients than photoperiods?** Autoflowers usually need less nutrient in total than photoperiods because they are smaller and live only 9–14 weeks, so start at a quarter to half of the label rate. They do not need weaker feed in flower: by then most run EC 1.2–1.8 mS/cm in coco. Underfeeding is as costly as overfeeding, because an auto can't extend its veg to catch up.

**Should I flush my autoflower before harvest?** No, don't flush an autoflower before harvest. Pre-harvest flushing is a myth, and harmful: plain water in the last one to two weeks starves the plant while it packs on most of its final weight and resin, and controlled work found it tended to lower yield. Keep feeding at stage strength. If you mix single salts, taper only nitrogen in the final weeks.

**When should I start feeding an autoflower?** Start feeding an autoflower at about week 2–3 from sprouting. In coco, feed lightly at every watering from the first true leaves, at EC 0.4–0.6 mS/cm. In quality bagged soil, water only until about week 3, when the seedling has used the starter charge. Raise strength gradually and judge by leaf tips: slight burnt tips mean back off.

## Sources

1. Caplan D, Dixon M, Zheng Y. 2017. Optimal rate of organic fertilizer during the vegetative-stage for cannabis grown in two coir-based substrates. HortScience 52(9):1307-1312. https://doi.org/10.21273/HORTSCI12401-17
2. Saloner A, Bernstein N. 2021. Nitrogen supply affects cannabinoid and terpenoid profile in medical cannabis (Cannabis sativa L.). Industrial Crops and Products 167:113516. https://doi.org/10.1016/j.indcrop.2021.113516
3. Alden MJ, Faust JE. 2025. Exploring the legacy practice of flushing in controlled-environment production of high-CBD cannabis. HortScience 60(10):1818-1825. https://doi.org/10.21273/HORTSCI18752-25