Autoflower Nutrient Schedule Week by Week (2026 Guide)
The exact autoflower nutrient schedule from seed to harvest — week-by-week PPM targets, feeding ratios, and flush timing. Stop guessing and start growing with precision.
Why Autoflowers Need Their Own Feeding Schedule
Autoflowers are not photoperiod plants in a smaller body — they are a fundamentally different beast. Their compact lifecycle (60–90 days seed to harvest) means they have no time to recover from overfeeding. The number one killer of autoflower crops is aggressive nutrients in the first three weeks. Unlike photoperiod plants, you cannot extend veg to recover from stress. This guide gives you the exact week-by-week PPM targets and feeding strategy to maximize yield without sacrificing one day of growth to nute issues.
Weeks 1–2: Seedling Stage (Less Is More)
During the seedling stage, your autoflower's root system is tiny and undeveloped. It cannot handle nutrient salts.
Weeks 1–2 targets:
- PPM: 100–200 (plain water or very light seedling formula)
- pH (soil): 6.3–6.5
- pH (coco/hydro): 5.8–6.0
- Feeding frequency: Water only. No nutrients until week 3.
If you are growing in a pre-amended soil like a quality pre-amended potting soil, there are enough nutrients for the first 3–4 weeks. Adding more will burn your seedlings. In coco coir, however, you must start a diluted feed (25% of recommended dose) from day 1 as coco has zero nutrients.
Watch for: Cotyledons (first round leaves) staying green and upright. Yellowing cotyledons this early signal overwatering, not nutrient deficiency.Weeks 3–4: Early Veg — Ramp Up Nitrogen
By week 3, your autoflower's root zone has expanded and you can begin feeding in earnest. This is the growth sprint phase.
Weeks 3–4 targets:
- PPM: 400–600
- Nitrogen (N) heavy — NPK ratio like 3-1-2
- Begin Cal-Mag supplementation: 2–5 ml/gal (critical in coco and soft water areas)
- Feeding frequency: Every watering in coco. Every other watering in soil.
With the a 3-part nutrient system, use your veg nutrient at 3 ml/gal and your base bloom nutrient at 3 ml/gal. Hold your bloom booster until pre-flower signs appear.
Always check runoff PPM. If runoff PPM is 300+ higher than your input, salts are building — cut feeding by 25% and water plain pH'd water next feeding.
Weeks 5–6: Pre-Flower Transition
Autoflowers show their first pistils (white hairs) anywhere from day 21 to day 35. Once you see these, the plant is shifting energy from leaf production to bud development. This is the most critical transition.
Weeks 5–6 targets:
- PPM: 600–800
- Begin transitioning to a bloom-focused feed: drop N, raise P and K
- Introduce your bloom booster or equivalent bloom booster at 50% dose
- Maintain Cal-Mag at 3–5 ml/gal
| Week |
Stage |
Target PPM |
Focus Nutrient |
| 1–2 | Seedling | 0–200 | Water only |
| 3–4 | Early Veg | 400–600 | Nitrogen + Cal-Mag |
| 5–6 | Pre-Flower | 600–800 | Transition to P/K |
| 7–9 | Full Flower | 800–1000 | Phosphorus + Potassium |
| 10–11 | Late Flower | 400–600 | Taper down |
| 12–13 | Flush | 0–150 | Plain pH'd water only |
Weeks 7–9: Peak Flowering — Maximum Phosphorus & Potassium
This is when the buds are stacking hard. Your plant is drinking nutrients aggressively to fuel bud development. Do not underfeed here — most growers lose yield in late flower from being too conservative.
Weeks 7–9 targets:
- PPM: 800–1000 (your highest point of the grow)
- Bloom-heavy feed: NPK ratio like 1-3-2
- your bloom booster at full dose: 4–5 ml/gal
- Optional: PK booster (like Canna PK 13/14) at weeks 7–8 for a brief spike
- Continue Cal-Mag: 3–4 ml/gal
Monitor trichomes with a jeweler's loupe or digital microscope. At this stage they should be mostly clear with a few turning cloudy. When 70–80% are cloudy and 10–20% amber, you are in the final countdown window. For a full harvest timing guide, see our
When to Harvest Cannabis guide.
Weeks 10–13: Late Flower, Taper & Flush
In the final 2 weeks before harvest, you need to clear the nutrient salts from the plant tissue to ensure a clean, smooth final product.
Weeks 10–11 — Taper: Gradually reduce PPM from 800 down to 400–500. Cut all N completely. Continue a light PK feed only.
Weeks 12–13 — Flush: Switch to plain, pH'd water only. Target runoff PPM below 150. The plant will begin drawing on its own stored nutrients (self-cannibalization), causing the fan leaves to yellow and die off naturally. This is a good sign, not a bad one — it means stored nutrients are being pulled into the buds.
Use a TDS meter to track your runoff PPM during flush. When it drops below 150, you are clear to harvest within 3–5 days.
Coco vs Soil: Does the Schedule Change?
Yes — significantly. Coco coir has zero buffered nutrients and acts more like a hydro medium. You must feed every watering from week 1 onward.
Key differences in coco:
- Start feeding (diluted) from day 1 — no plain water week in coco
- pH range is tighter: 5.8–6.0 strictly
- Cal-Mag is non-negotiable — coco naturally binds calcium and magnesium
- Use a coco-specific nutrient line like a 3-part hydro nutrient line or a coco-specific nutrient line for best results
- Flush is less critical in coco than soil — a 3–5 day flush is sufficient
For a full deep-dive into growing in coco, see our
Coco Coir Grow Guide.
Frequently Asked Questions
What nutrients do autoflowers need?
Autoflowers need a complete macro and micro nutrient profile: Nitrogen (N), Phosphorus (P), Potassium (K), Calcium, Magnesium, and a full suite of micronutrients. The ratio shifts from N-heavy during veg (weeks 3–4) to P/K-heavy during flower (weeks 7–9). Cal-Mag supplementation is essential in coco and RO/soft water grows.
When do I start feeding autoflowers nutrients?
In pre-amended soil (like a quality pre-amended potting soil), hold off feeding until week 3–4. In coco coir or plain soil, begin a 25% diluted feed from day 1 of seedling as these mediums have no buffered nutrients.
What PPM should autoflowers be fed?
Start at 0–200 PPM for seedlings (weeks 1–2), ramp to 400–600 PPM in early veg (weeks 3–4), peak at 800–1000 PPM during full flower (weeks 7–9), then taper back down to 0–150 PPM during the final flush.
Can you overfeed autoflowers?
Yes — autoflowers are more sensitive to overfeeding than photoperiod plants because they have no recovery time in their 60–90 day lifecycle. Always start at 50–75% of the manufacturer's recommended dose and increase only if no signs of burn appear after 3–4 days.
How long should you flush autoflowers before harvest?
Flush with plain pH'd water for 5–10 days in soil, or 3–5 days in coco. Use a TDS meter to track runoff PPM — harvest when runoff drops below 150 PPM. Natural leaf yellowing during flush is a positive sign.
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