The question I get more than any other from auto growers isn’t about light schedules or training — it’s about feeding. Specifically: how much, when, and whether the strain they’re running needs different treatment to the last one. The short answer is yes, it does. The slightly longer answer is the reason I wrote this.
Most EC guides treat autoflowers as a single category. Start at 0.4, build to 1.6, flush at the end. That’s not wrong exactly, but it leaves out the part that actually matters — which is that the genetics sitting inside that ruderalis cross determine how the plant responds to nutrients more than the ruderalis itself does. An Auto Godfather OG and an Auto Super Skunk are not the same plant. They don’t want the same feed. Treating them identically is how you get tip burn on one and a hungry, underfed plant on the other.
What follows is strain-by-strain feeding guidance for the autos in the Sacred Seeds catalogue. I’ve grouped them by genetic character — OG/Kush sensitive, classic indica stable, sativa-dominant longer timeline, candy/exotic, high-resin powerhouses, and the one genuinely robust skunk cross. The master reference table at the top gives you the numbers. The sections below it give you the why. Both matter.
Before the Table — Three Rules That Apply to Every Auto
Rule 1: The fixed timeline means every mistake compounds. A photoperiod plant that gets overfed in week two can be held in veg while it recovers. An auto that gets overfed in week two loses that recovery time permanently. The fixed timeline is the whole reason auto feeding discipline matters more than photoperiod feeding discipline — not less.
Rule 2: Nutrient labels are written for photoperiods. Almost every nutrient brand’s feeding schedule assumes a photoperiod plant with a long veg stage and a flexible timeline. Running those schedules at full strength on an auto will burn most strains. The strain-specific EC targets below are what actually works — consistently lower than the label, consistently better results.
Rule 3: Watch the tips, not the calendar. The clearest signal that you’re at the right EC is clean, crisp leaf tips with healthy green colour. The clearest signal you’ve gone too far is tip burn — brown, curling tips — which appears 3–5 days after the overfeed event, not immediately. If you see tip burn, drop EC by 25% and run plain pH-adjusted water for two sessions before reintroducing nutrients.
📊 Sacred Seeds Auto EC Reference — All 18 Strains
EC targets in mS/cm for coco/perlite or soil grows. Hydro growers: reduce all figures by 10–15%. pH: 6.0–6.2 for coco, 6.2–6.5 for soil.
| Strain | Sensitivity | Seedling Days 1–14 |
Early veg Days 14–28 |
Peak flower Weeks 5–8 |
Late flower Final 2 wks |
Key note |
|---|---|---|---|---|---|---|
| OG / KUSH CROSSES — SENSITIVE | ||||||
| Auto Godfather OG | High | 0.3–0.4 | 0.8–1.0 | 1.4–1.6 | 0.4–0.6 | OG genetics carry photoperiod nutrient sensitivity. Tip burn arrives fast. Never push above 1.6 in flower. |
| Auto Purple Kush | High | 0.3–0.4 | 0.8–1.0 | 1.3–1.5 | 0.4–0.6 | Pure Kush indica — lowest EC ceiling in the catalogue. Cool nights trigger purple without extra potassium. |
| Auto Girl Scout Cookies | High | 0.3–0.4 | 0.8–1.0 | 1.4–1.6 | 0.4–0.6 | Cookie genetics carry OG nutrient sensitivity. Excess nitrogen in flower kills the caryophyllene terpene profile. |
| CLASSIC INDICA CROSSES — STABLE | ||||||
| Auto Northern Lights | Low | 0.4–0.6 | 1.0–1.2 | 1.6–1.8 | 0.4–0.6 | Most forgiving classic indica in the catalogue. Afghan-dominant genetics handle moderate EC well. The safest strain for newer auto growers. |
| Auto White Widow | Low | 0.4–0.6 | 1.0–1.2 | 1.6–1.8 | 0.4–0.6 | Brazilian/South Indian genetics are robust. Consistent mid-range feeder. The crystal resin production benefits from potassium support from week 5. |
| Auto Granddaddy Purple | Medium | 0.4–0.5 | 0.9–1.1 | 1.4–1.6 | 0.4–0.6 | Purple Urkle × Big Bud cross. Cool nights (18–20°C) in weeks 7–9 are more effective for purple development than extra potassium. Don’t push EC trying to force colour. |
| Auto Blue Dream | Medium | 0.4–0.5 | 1.0–1.2 | 1.5–1.7 | 0.4–0.6 | Blueberry × Haze cross sits between the indica and sativa groups. Slight sativa sensitivity in late veg — watch for nitrogen dark-green clawing at week 3. |
| SATIVA-DOMINANT — LONGER TIMELINE | ||||||
| Auto Amnesia Haze | High | 0.3–0.4 | 0.8–1.0 | 1.4–1.6 | 0.4–0.6 | Haze genetics are notably nutrient-sensitive — this is well-documented across grow diaries. Overfeeding produces excess foliage at the expense of bud development. Longer timeline (10–12 weeks) does allow gradual build. |
| Auto Jack Herer | Medium | 0.4–0.5 | 1.0–1.2 | 1.5–1.7 | 0.4–0.6 | Haze × Northern Lights × Shiva Skunk. The skunk and NL genetics moderate the Haze sensitivity. Pine terpene profile is compromised by nitrogen excess in late flower — back off early. |
| Auto Moby Dick | Medium | 0.4–0.5 | 1.0–1.2 | 1.6–1.8 | 0.4–0.6 | Amnesia Haze × White Widow cross. The White Widow genetics add robustness that the pure Haze doesn’t have. One of the higher-feeding sativa autos in the catalogue. |
| Auto Bruce Banner | Medium | 0.4–0.5 | 1.0–1.2 | 1.6–1.8 | 0.4–0.6 | OG Kush × Strawberry Diesel. The diesel genetics allow higher mid-flower EC than OG-dominant strains. Growers consistently report it handles 1.7–1.8 in mid flower with dialled root zone. |
| CANDY / EXOTIC GENETICS | ||||||
| Auto Gorilla Zkittlez | Medium | 0.4–0.5 | 1.0–1.2 | 1.5–1.7 | 0.4–0.6 | GG4 × Zkittlez cross sits between parent sensitivities. GG4 robustness tempers the Zkittlez appetite. The fruity terpene profile is nitrogen-sensitive in late flower — ease off from week 6. |
| Auto Runtz | Medium | 0.4–0.5 | 1.0–1.2 | 1.5–1.7 | 0.4–0.6 | Zkittlez × Gelato. Moderate feeder. The bag appeal depends heavily on clean late-flower conditions — keep RH 45–50% and EC conservative from week 7 onward. |
| Auto Pineapple Express | Low | 0.4–0.5 | 1.0–1.2 | 1.5–1.7 | 0.4–0.6 | Trainwreck × Hawaiian genetics are robust. One of the easier tropical-terpene autos to feed. Consistent mid-range feeder — follow the tips and adjust accordingly. |
| HIGH-RESIN POWERHOUSES | ||||||
| Auto Gorilla Glue | Low | 0.4–0.6 | 1.0–1.3 | 1.7–2.0 | 0.4–0.6 | Chem Sister × Sour Dubb × Chocolate Diesel. The highest EC ceiling of any auto in the catalogue. Forum growers consistently report GG4 handles higher EC than expected. Still start light — the genetics allow it, not demand it. |
| Auto Fat Bastard | Medium | 0.4–0.5 | 1.0–1.2 | 1.6–1.8 | 0.4–0.6 | Goldmember × Monkey Spunk. A hungry strain that rewards feeding — but the OG ancestry means it will show tip burn if pushed past 1.8. Potassium support from week 5 improves resin density noticeably. |
| Auto Psychedelic (LSD) | Medium | 0.4–0.5 | 1.0–1.2 | 1.5–1.7 | 0.4–0.6 | Skunk × Mazar genetics. The high-resin expression is nitrogen-sensitive in late flower — back off nitrogen by week 6 to protect trichome development. |
| SKUNK — MOST ROBUST | ||||||
| Auto Super Skunk | Low | 0.4–0.6 | 1.0–1.3 | 1.6–2.0 | 0.4–0.6 | Skunk #1 × Afghan. The most ruderalis-compatible genetics in the catalogue. Most forgiving auto we stock. The one strain where pushing toward the top of the EC range is least likely to cause problems. |
EC figures are guides, not rules. Always read the plant. Tip burn = drop EC. Pale, hungry-looking growth = consider building slightly. The tips don’t lie.
🌿 Group 1 — OG and Kush Crosses: Treat With Respect
Strains: Auto Godfather OG, Auto Purple Kush, Auto Girl Scout Cookies
The genetics that define these three strains — XXX OG × Alpha OG for Godfather OG, pure Kush landrace for Purple Kush, OG Kush × Durban for GSC — carry nutrient sensitivity as a characteristic trait regardless of whether you’re growing the photoperiod or the auto version. This is one of the things that gets under-discussed in auto growing: the Ruderalis cross changes the light dependency and shortens the timeline, but it doesn’t change the photoperiod parent’s fundamental relationship with nutrients.
What that means in practice: these three are the strains where I’ve seen the most tip burn from growers who ran a generic auto feeding schedule. The damage typically shows up at day 18–22, at exactly the point where many growers are starting to build EC toward week 3 targets. By then it’s too late to recover cleanly — the fixed timeline is already running.
My approach with OG and Kush auto genetics: no nutrients for the first 14 days regardless of medium, first feed at 0.3–0.4 EC, and I build very gradually toward 1.4–1.6 at peak flower. I’ve never pushed an Auto Godfather OG above 1.6 and seen a better result than one run conservatively at 1.5. The genetics don’t reward pushing. What they reward is precision.
Auto Girl Scout Cookies — the terpene note
GSC’s defining characteristic is the caryophyllene-dominant terpene profile — the baked goods and cookie dough aroma. That profile is nitrogen-sensitive in flower. Excess nitrogen in weeks 5–7 consistently produces extra foliage at the expense of resin and terpene development. I bring nitrogen down aggressively from week 5 onward with Auto GSC specifically — more aggressively than with the other OG crosses. The growers who get the best GSC results are the ones who let the plant go a little pale in late flower rather than chasing dark green leaves. Pale is fine. Tip burn is not.
🌿 Group 2 — Classic Indica Crosses: Reliable Mid-Range Feeders
Strains: Auto Northern Lights, Auto White Widow, Auto Granddaddy Purple, Auto Blue Dream
These are the straightforward ones. Not because autos are ever entirely straightforward — the fixed timeline rule applies equally — but because the genetics underneath the ruderalis cross are robust, tested strains that have been grown in every condition imaginable. Northern Lights’ Afghan genetics, White Widow’s Brazilian/South Indian cross, GDP’s Purple Urkle × Big Bud, Blue Dream’s Blueberry × Haze — all of them have decades of cultivation history showing what they can handle.
Auto Northern Lights is the most forgiving auto in the catalogue. I’d recommend it to any grower running their first auto specifically because the genetics absorb minor feeding mistakes better than any other strain we stock. You’ll still see tip burn if you push hard enough, but the threshold is meaningfully higher than the OG and Kush crosses.
Auto White Widow is the same category — robust, predictable, consistent. The crystal resin production that made the photoperiod famous carries through the auto cross reliably. One thing worth noting: potassium support from week 5 of flower improves the resin density on White Widow noticeably. Not a heavy K boost — just maintaining K at the high end of the bloom ratio rather than letting it taper. I’ve seen a clear difference in trichome coverage between White Widow runs where I’ve been deliberate about this and runs where I haven’t.
Auto Granddaddy Purple sits in this group but with one specific note: growers often try to push higher potassium to drive the purple colouration. This is the wrong lever. The purple in GDP comes from temperature — specifically the anthocyanin expression triggered by cool nights in late flower. If you’re running GDP and want purple, drop your night temperature to 18–20°C in weeks 7–9. That’s what does it. Pushing K doesn’t replicate the effect and risks imbalancing the feed at exactly the point where the terpene expression is developing.
🌿 Group 3 — Sativa-Dominant Autos: Longer Timeline, Nuanced Sensitivity
Strains: Auto Amnesia Haze, Auto Jack Herer, Auto Moby Dick, Auto Bruce Banner
This group is the most nuanced because the longer fixed timelines — 10–12 weeks for Amnesia Haze and Moby Dick, versus 8–9 for most indica-dominant autos — mean you have more time to build EC gradually, but the sativa genetics carry their own sensitivity profile that changes the equation.
Haze genetics specifically are nutrient-sensitive. This is consistent across grow diary data and consistent with what I’ve seen personally. Auto Amnesia Haze shows overfeeding symptoms — excess foliage, airy bud development, compromised terpene expression — before it shows classic tip burn in many cases. The plant responds to overfeeding by putting energy into leaf production rather than bud and resin development. The indicator to watch isn’t just the tips — it’s whether the canopy is getting leafier rather than budding. If that’s happening in weeks 4–6, EC is too high.
Auto Moby Dick is a different case. The Amnesia Haze × White Widow cross gets robustness from the White Widow genetics that the pure Haze auto doesn’t have. In practice this means Moby Dick can push toward 1.8 at peak flower without the same foliage-over-bud response you’d see from Auto Amnesia Haze. It’s still a moderate feeder, not an aggressive one — but growers who’ve run both will notice the difference.
Auto Bruce Banner surprises people because OG Kush is in the lineage. But the Strawberry Diesel cross adds robustness that the pure OG crosses don’t have, and forum growers consistently run it at 1.7–1.8 in mid-flower with good results. The key qualifier is “with dialled root zone” — good drainage, good coco buffering, and runoff monitoring. If those fundamentals are right, Bruce Banner can handle higher EC than its OG parentage suggests.
The nitrogen timing rule for sativa autos
With all four strains in this group, nitrogen needs to come down earlier than growers expect. Most indica-dominant autos can carry nitrogen relatively deep into flower — weeks 6–7 — before you risk affecting bud quality. Sativa-dominant autos should be transitioning away from nitrogen emphasis by weeks 4–5 of flower and running low nitrogen by week 6. The sativa flowering stretch is complete by then and any nitrogen the plant is still receiving is going into foliage rather than buds. Bring it down early. The terpene expression thanks you for it.
🌿 Group 4 — Candy and Exotic Genetics: Feed the Plant, Protect the Terpenes
Strains: Auto Gorilla Zkittlez, Auto Runtz, Auto Pineapple Express
The candy and tropical-terpene genetics are interesting because the thing that makes them exceptional — the fruity, candy, tropical terpene profiles — is also the thing most directly at risk from incorrect feeding. Nitrogen excess in the second half of flower doesn’t just affect yield in these strains, it actively mutes the terpene expression that defines them. A grower who overfeeds Auto Runtz in weeks 5–7 and then wonders why it doesn’t smell like candy is experiencing exactly this.
Auto Gorilla Zkittlez carries the Zkittlez side of the family in this catalogue, and it sits between GG4 and Zkittlez genetics in terms of feeding tolerance — which means it can push slightly higher than a pure Zkittlez expression without the same foliage response, but it still needs careful late-flower nitrogen management. The GG4 robustness is real but it doesn’t override the candy terpene sensitivity. The feeding pattern is nitrogen-forward in veg and early flower, then a deliberate shift to P and K dominance from week 5 onward. Let the nitrogen drop. The terpene profile depends on it.
Auto Pineapple Express is the most straightforward in this group. Trainwreck × Hawaiian genetics are robust tropical plants that handle moderate EC well. The pine and citrus terpene profile is less nitrogen-sensitive than the candy profiles. A reliable mid-range feeder that follows the tips and responds predictably.
🌿 Group 5 — High-Resin Powerhouses: Precision Pays Off
Strains: Auto Gorilla Glue, Auto Fat Bastard, Auto Psychedelic
Auto Gorilla Glue sits at the top of the EC tolerance range for autos. The Chem Sister × Sour Dubb × Chocolate Diesel genetics are genuinely robust — this is one of the things that made GG4 one of the most grown strains of the past decade — and that robustness carries through into the auto version more clearly than with most photoperiod crosses. Grow diary data consistently shows Auto GG4 handling EC in the 1.8–2.0 range in peak flower without the tip burn response you’d see from OG or Kush crosses at the same level.
I want to be clear about what this means: it means the ceiling is higher, not that you should start high. Auto GG4 still gets nothing for the first 14 days and builds from 0.4–0.6 in the same way as every other strain. What changes is where the ceiling sits. If you’ve got a well-dialled coco setup with proper drainage, good airflow, and you’ve been building gradually — Auto GG4 can push toward 2.0 at peak flower and produce better resin density and yield for it. Most other autos can’t say that.
Auto Fat Bastard is a hungry strain. The Goldmember × Monkey Spunk genetics from Blimburn produce a large, dense plant that benefits from nutrients being present through the full flowering cycle. But the OG ancestry is real — above 1.8 you’ll start seeing tip stress. Potassium support from week 5 is where the resin density improvement shows most clearly with Fat Bastard specifically. I’ve run it with and without deliberate K emphasis in mid-flower and the trichome coverage difference is visible at harvest.
One auto that used to live in this group has moved across to our sister brand. Auto Permanent Marker and the rest of the post-2020 modern exotics sit on Sigma now, and the strain-specific feeding detail for that delicate Biscotti and Gary Payton lineage lives there with them. If you’re running one of those, that’s where to look.
🌿 Group 6 — Auto Super Skunk: The One That Earns Its Ruderalis Cross
Strains: Auto Super Skunk
Super Skunk deserves its own section because it sits in a genuinely different category to everything else in the catalogue. Skunk #1 × Afghan is arguably the most ruderalis-compatible genetic combination that exists in mainstream cannabis — both parents are robust, stable, forgiving plants whose characteristics translate well through the auto cross. The result is an auto that handles moderate feeding mistakes more cleanly than any other strain here.
This is the one strain where I’ll tell growers: if you’re new to autos and you’ve been timid about EC because you’ve burned something before, Auto Super Skunk is where you can start learning to push a little. Not recklessly — start light, read the tips, build gradually. But the ceiling is 2.0 EC at peak flower for a well-dialled grow, and the plant gets there without the sensitivity drama of the OG and Haze crosses. It’s also the strain I’d recommend for a grower running their first coco grow specifically, because the forgiving genetics give you room to learn the medium while the plant absorbs minor mistakes.
🧠 Jason’s Note — What the EC Table Doesn’t Tell You
Numbers are a guide, not a guarantee. The EC targets in the table above are where I’d aim based on what these genetics consistently show — but your medium, your water quality, your root zone health, and your environment all modify the equation.
If you’re running coco, reduce the peak EC targets by 10–15% compared to soil — coco delivers nutrients to the roots more efficiently and the margin for error is smaller. If you’re using hard tap water (EC above 0.5 from the tap), subtract your base water EC from the target before you add nutrients. If your root zone is restricted — pot too small, overwatering history — even a strain with a high EC ceiling will burn at lower levels than the table suggests.
The most consistent mistake I see isn’t running the wrong EC for the strain — it’s running the right EC into a compromised root zone. Get your container, medium, drainage, and watering frequency right first. The EC targets will behave as described once the foundation is there. If you’re seeing unexpected burning at moderate EC, look at the root zone before you look at the nutrient schedule.
📋 Flush Timing by Genetic Group
Flushing removes accumulated salts from the medium and allows the plant to draw on its stored nutrients in the final days — which improves flavour and the cleanliness of the smoke. The timing varies by how long the flowering timeline runs and how aggressive the feeding programme was.
| Genetic group | Flush start | Duration |
|---|---|---|
| OG/Kush crosses (sensitive) | 10–14 days before harvest | Longer flush helps terpene expression particularly with OG and Cookie genetics |
| Classic indica crosses | 7–10 days before harvest | Standard flush — stable genetics don’t need the extended window |
| Sativa-dominant (longer timeline) | 10–14 days before harvest | Haze and sativa terpenes express better after a clean finish — don’t rush this |
| Candy/exotic genetics | 10–14 days before harvest | The fruity candy terpene profile is significantly cleaner post-flush. Don’t shorten this window. |
| High-resin powerhouses | 7–10 days before harvest | GG4 and Fat Bastard can carry a slightly shorter flush given the robust genetics. |
| Auto Super Skunk | 7 days before harvest | Shortest flush window — the robust genetics don’t accumulate salt stress the way sensitive crosses do |
Browse the full autoflowering cannabis seeds range at Sacred Seeds Australia — every strain in this guide is in stock with express Australian shipping and batch-tested viability. The main cannabis seeds catalogue includes both auto and photoperiod options across all the same genetics.
❓ Frequently Asked Questions — Autoflower EC and Feeding
Do all autoflowers need the same EC?
No — and treating them as if they do is one of the most consistent sources of feeding problems with autos. The genetics inside the ruderalis cross determine nutrient sensitivity more than the ruderalis itself does. OG and Kush crosses (Auto Godfather OG, Auto Purple Kush, Auto GSC) are significantly more sensitive than robust indica crosses (Auto Northern Lights, Auto White Widow) or high-resin diesel genetics (Auto Gorilla Glue). The reference table above maps every strain in the Sacred Seeds auto catalogue to its specific EC targets and sensitivity rating.
Why are autoflowers more sensitive to nutrients than photoperiods?
Three reasons. First, the fixed timeline means mistakes compound rather than correct — a photoperiod plant in veg can absorb a feeding error because you can extend the veg phase while it recovers. An auto can’t. Second, autos typically have a smaller root zone in a smaller container, which means less buffering capacity between the nutrient solution and the root. Third, the compressed timeline means the seedling stage — where feeding tolerance is lowest — runs straight into the vegetative and pre-flower stages without recovery time between them. Start conservative, build slowly, and read the plant.
What EC should I start feeding autoflowers?
0.3–0.6 EC for the first feed, depending on genetics. Sensitive OG and Kush crosses start at 0.3–0.4. Robust indica and skunk crosses can start at 0.4–0.6. The first feed should happen when the third node is clearly developing — usually days 14–21 from germination. Before that point, a seedling in good medium doesn’t need nutrients. The full seedling feeding guide covers first feed timing in detail.
How do I know if my EC is too high?
Tip burn is the first signal — the very tips of the serrated leaf edges browning and curling slightly. It appears 3–5 days after the overfeed event, not immediately. Other signs: leaves cupping downward (nitrogen toxicity), deep blue-green colouration, and in severe cases, leaf clawing where tips hook downward sharply. If you see tip burn, drop EC by 25% and run plain pH-adjusted water for two sessions before reintroducing nutrients at the lower level.
Should I flush autoflowers before harvest?
Yes — and the timing depends on genetics. OG/Kush crosses, sativa-dominant autos, and candy/exotic genetics benefit from 10–14 days of plain pH-adjusted water before harvest. Classic indica crosses and high-resin powerhouses can use a 7–10 day window. Auto Super Skunk manages with 7 days. The flush clears accumulated salts from the medium and allows the terpene profile to express cleanly — it makes a noticeable difference to flavour and smoke quality, particularly with terpene-sensitive genetics like Auto GSC, Auto Amnesia Haze, and the candy strains.
What’s the highest EC I can run with an autoflower?
Auto Gorilla Glue and Auto Super Skunk can push toward 2.0 EC at peak flower with a well-dialled root zone. Most other autos in the catalogue peak at 1.6–1.8. Sensitive OG and Kush crosses shouldn’t exceed 1.5–1.6 even under ideal conditions. These are upper limits — not targets to aim for from the start. Build gradually from the seedling stage and let the plant’s response guide where you settle.
Does the same EC guidance apply to coco and soil?
The principles are the same but coco requires slightly lower EC targets — approximately 10–15% below the figures in the table. Coco delivers nutrients to the root zone more efficiently than soil, which means the effective concentration at the root is higher than in soil at the same input EC. Coco also requires more frequent watering (often daily) which affects how nutrients accumulate. If you’re running coco, monitor runoff EC alongside input EC — if runoff EC is climbing significantly above input, the root zone is accumulating salt and you need to flush and reduce.
