Forbidden Glue Auto Feminized: Review & Grow Guide

_Published June 29, 2026 · Updated June 29, 2026 · Written by Head Honcho, PPS master cultivator._

Key takeaways

• Genetics: PPS lists Zkittlez × GG4 × Lemon × ruderalis — a flavour-chaser cross that throws several phenotypes per pack.
• Potency: breeder data puts THC at 20–25%, CBD under 1% (~0.7%) — commonly associated with evening relaxation, not a wake-and-bake.
• Speed: seed to harvest in 56–63 days (8–9 weeks), with no light-schedule change.
• Yield: 400–500 g/m² indoors with gentle early training and tight humidity control; 50–150 g per plant outdoors.
• Looks: purple phenotype likely when late-flower nights drop to ~10–13 °C in weeks 5–7.
• Made for: Canadian indoor tents and short-season outdoor grows in southern QC, ON, and BC.

On this page

• Effects & terpenes
• Potency
• Grow guide
• Week-by-week
• Purple phenotype
• Harvest
• Problems
• Outdoor in Canada
• vs Gorilla Glue #4
• FAQ

What does Forbidden Glue Auto Feminized taste and smell like?

Open a jar and the room knows. The aroma of Forbidden Glue Auto Feminized is citrus and diesel up front — sharp lemon zest and orange peel from limonene, layered over a gassy, fuel-like base. Underneath sits a peppery, spiced note from caryophyllene (the same terpene found in black pepper and cloves) and an earthy, musky finish from myrcene. PPS lists the dominant terpene trio as limonene, caryophyllene, and myrcene, and it shows: this is not a subtle strain, and it doesn't pretend to be. The intensity is one reason it needs a carbon filter in a home tent — the smell carries, especially in the last two weeks when resin production peaks.

That loud profile is a direct read-out of the genetics. Breeder data lists the cross as Zkittlez × Gorilla Glue #4 × Lemon × ruderalis, an indica-dominant build at roughly 60/40 indica, and each parent pulls its weight. Zkittlez brings the sweet, fruity top notes and the genetic predisposition for purple coloration — it's the source of both the candy sweetness and the anthocyanin pigments that colour the buds. Gorilla Glue #4 contributes the heavy resin, the gassy diesel backbone, and the sticky bud density the Glue family is famous for; it's also where the strain gets its weight and its heavy, relaxing finish. Lemon brightens the whole profile with a sharp citrus that keeps the diesel from going flat. Ruderalis hands the plant its autoflowering trigger — flowering on age rather than on a changing light cycle — plus a compact, fast structure suited to short Canadian summers, the trade-off being a slightly lower ceiling on size than a photoperiod plant of the same lineage. If you want to understand how indica and sativa genetics shape plant structure and effect, our sativa vs indica plant guide breaks it down.

The flavour follows the nose, but cleaner. Cured properly — slow-dried over 10 to 14 days, then jarred and burped for two to three weeks — the smoke is smooth and the taste carries from the first pull to the last: bright citrus on the inhale, diesel and spice on the exhale, with a sweet candy note on the back end from the Zkittlez side. Because it's a multi-way cross, expect variation across a pack: fruit-forward phenotypes push the Zkittlez sweetness to the front, while fuel-forward phenotypes emphasise the GG4 diesel and leave the lemon as a top note. That same loud terpene load is also why Forbidden Glue Auto Feminized is so prized for concentrates — high resin density plus an expressive profile makes for hash and rosin that taste like the living plant.

How strong is Forbidden Glue Auto Feminized?

Breeder data puts THC at 20–25% with CBD under 1% (around 0.7%), so Forbidden Glue Auto Feminized leans fully into its THC rather than tempering it. The effect is progressive and weighted, and it rewards a little experience. The onset is cerebral and uplifting — a clear mental brightness within minutes that peaks around the 15–20 minute mark, bringing a spark of euphoria and focus. There's a brief window where it feels almost sativa-like: talkative, light, a little creative.

Then the indica takes over. As the myrcene-heavy base asserts itself, the high pulls down into a deep, full-body relaxation; by roughly 45 minutes most people feel a pronounced body weight in the limbs and a loosening through the shoulders and jaw. At moderate doses it's relaxed-but-functional — fine for a movie, a meal, or quiet company. Push the dose and the heavy finish takes hold, the kind that ends with you horizontal and the lights low. Many growers describe it as better suited to late-day use — an after-dinner, wind-down strain that's commonly associated with evening relaxation rather than a daytime cultivar. The negligible CBD means there's nothing in the chemistry to soften that THC-forward character, which is exactly what its fans want from it.

Worth knowing for dosing: the 20–25% THC range is a spread, not a fixed number, and where a given plant lands depends on phenotype, ripeness, and how carefully it was cured. A fuel-forward GG4-leaning pheno harvested with a little more amber will feel heavier and more sedating than a fruit-forward Zkittlez-leaning one cut at peak milky, even from the same pack. Treat the first jar as a calibration run — start with a smaller amount than you would with a known strain, see where the curve lands for the specific phenotype you grew, and adjust from there. The progressive onset also means it pays to wait: the cerebral front end can tempt a re-dose before the body half has arrived, and the back end of this strain does most of the heavy lifting.

How to grow Forbidden Glue Auto Feminized for maximum yield

Forbidden Glue Auto Feminized has the genetics to hit 400–500 g/m² indoors, but autoflowers don't forgive sloppy environments — the timeline is too short to recover from a mistake. A photoperiod plant gives you weeks of veg to fix a deficiency or bounce back from heat stress. An auto gives you days. The good news: dial in four things — training, humidity, feeding, and light schedule — and this plant performs.

Light, pot size, LST, nutrients and humidity

Train gently and early. You can't run aggressive high-stress training on a fast autoflower — there's no veg buffer for the plant to recover before flowering locks structure in place. Instead, use low-stress training (LST) during weeks 2–4: soft plant ties or coated wire to bend branch tips away from the centre, opening the canopy so light reaches the lower bud sites instead of just the top cola. Start as soon as the plant is tall enough to tie down without snapping, work the main stem and the first two or three branch pairs, then stop by week 4 and let her flower in peace. Done right, LST alone can turn a single dominant cola into four or five competitive ones and add real weight to the harvest.

Pick the right pot. Pair the grow with a quality 5-gallon fabric pot — fabric breathes, prevents the root circling that stunts autos, and is one of the cheapest yield upgrades you can make. Autos hate transplant shock, so start the seed in the container you intend to finish in rather than potting up partway through.

Lock the light schedule. Run 18/6 or 20/4 for the entire cycle — no switching. Because the plant flowers on age, not light, you never trip a 12/12 flip; you just keep the lights on the same way from seedling to harvest. 20/4 nudges size and yield up a few percent but costs more in electricity; 18/6 is the sweet spot for Canadian home growers balancing harvest against hydro bills, and it gives roots a longer dark window to respire.

Give it enough light intensity. Schedule is only half the equation — intensity matters just as much for hitting that 400–500 g/m² ceiling. A dense, resin-heavy indica like this one wants real photon density to fill out its colas, so a quality LED running roughly 600–800 µmol/m²/s at the canopy through flower is the target for a single-plant or small-tent grow. Keep the fixture at the manufacturer's recommended hang height and watch the plant rather than the spec sheet: leaves that taco or bleach at the tops are getting too much, while loose, stretchy growth and airy lower buds usually mean too little. Raising the light a few centimetres during the seedling and stretch phases, then bringing it down as the canopy thickens, tracks the plant's changing demand and protects those tender early leaves.

Feed light. Autoflowers are sensitive eaters and this one is no exception — its compact size means it simply needs less than a sprawling photoperiod plant, and overfeeding shows up fast as clawed, burnt leaf tips. Start at roughly 50% of the recommended strength in week 2 and increase only if the plant asks for it with pale new growth. As flowering sets in (weeks 5–6), ease off nitrogen and lift phosphorus and potassium to drive bud density and resin. In the final two weeks, flush with plain pH'd water to clear residual salts — it cleans up the smoke, improves the burn, and lets the terpenes come through without a chemical edge.

Control humidity hard during flower. That dense, resinous bud structure is both the prize and the risk — tight internodes and heavy resin trap moisture and invite mould if relative humidity climbs above 50% in weeks 7–8. Target 40–45% RH from week 5 onward, run a calibrated hygrometer at canopy height, and keep exhaust airflow strong with an oscillating fan moving air through the canopy, not just over it. Lower RH doesn't hurt resin — it actually preserves terpenes and keeps trichomes frosty, and it's the single biggest lever you have against bud rot in a dense indica. For a refresher on how the flowering stage actually unfolds week by week, see our cannabis flowering stage guide, and the broader autoflowering growing guide explains how the ruderalis trait changes the way you run the whole grow.

Forbidden Glue Auto Feminized week-by-week grow schedule

Forbidden Glue Auto Feminized runs roughly 56–63 days from seed to harvest on an 18/6 or 20/4 light schedule that never changes. A typical timeline: germination (days 1–4), seedling (week 1), vegetative growth (weeks 2–3), pre-flower stretch (week 4), flower fill (weeks 5–7), ripening and flush (weeks 8–9), then harvest once trichomes turn milky. Below is what to do at each phase.

Germination — days 1–4. Pop the seed using the blue paper towel method: a damp (not soaking) paper towel between two plates, kept warm and dark at around 22–25 °C. The taproot usually shows in 24–72 hours. Plant it root-down about 1 cm deep into its final container — autos hate transplant shock, so start in the pot you'll finish in. Our germination guarantee covers you if a seed doesn't crack.

Seedling — week 1. Keep things humid (60–70% RH) and the light gentle and a bit higher off the canopy. Water sparingly around the stem, not the whole pot, so the small root system reaches outward. No nutrients yet — the seed's own reserves feed the first set of true leaves. This is the most fragile phase, so resist the urge to fuss.

Vegetative growth — weeks 2–3. The plant builds its frame fast now. Begin light feeding at ~50% strength, start your LST as soon as she's tall enough to tie down, and drop humidity toward 50–55%. Watch internode spacing: tight nodes mean a healthy, well-lit plant. This is your only real window to shape the canopy, so use it.

Pre-flower stretch — week 4. Autos transition on their own clock; you'll see the first white pistils and a burst of vertical stretch. Finish any LST now and stop training — once flowers set, the structure is locked. Ease nitrogen down and introduce bloom nutrients. Get airflow dialled before the canopy fills in.

Flower fill — weeks 5–7. Buds form and fatten, resin coats the calyxes, and the smell turns loud. Hold RH at 40–45% and keep air moving through the canopy. This is the window to drop night temps to ~10–13 °C if you want the purple phenotype. Feed phosphorus and potassium for density; defoliate lightly only where leaves shade bud sites.

Ripening and flush — weeks 8–9. Pistils darken and curl, trichomes shift from clear to milky. Begin a plain-water flush for the final 10–14 days to clear salts. Start checking trichomes daily with a loupe. Patience here is what separates a good jar from a great one.

Harvest. Cut when 70–80% of trichomes are milky with 10–20% amber. Trim, then slow-dry over 10–14 days at 18–20 °C and 55–60% RH before jarring and curing. For the technique in detail, see our cannabis flowering stage guide.

Why does Forbidden Glue Auto Feminized turn purple?

The purple is real, and it comes from the Zkittlez side of the cross. Purple coloration in cannabis is produced by anthocyanins — water-soluble pigments that emerge when night-time temperatures drop during late flower. The genetics have to be there (Zkittlez supplies them), but environment is the trigger: if nights stay warm, even a purple-capable plant finishes green. Not every plant in a pack will turn — the trait segregates — so think of purple as a likely bonus rather than a guarantee.

Indoors, drop night-time temperature to roughly 10–13 °C during weeks 5–7 of flowering (autoflowers express on a compressed timeline, so the cooling window comes earlier than on photoperiod plants). The day-to-night temperature swing is what does the work — a flat, warm 24-hour profile won't trigger the colour even with the genetics present. Hold humidity at 40–45% so the cold doesn't invite bud rot, and keep air moving — cold, stagnant, humid air is exactly where mould starts, and a dense indica in cool conditions is the worst-case combination if airflow is poor. Outdoors in Canada, late-August and September nights often do the job for free; pick a spot that cools quickly after sunset and isn't trapping daytime heat into the night.

One honest note: purple buds are not more potent. Anthocyanins have no psychoactive effect and minimal flavour impact — a purple phenotype carries the same THC and terpenes as a green one from the same pack. The payoff is purely visual. For many growers that's reason enough; the buds photograph beautifully, hold their colour through the cure, and feel like a reward at harvest after a careful run.

When should you harvest Forbidden Glue Auto Feminized?

Harvest timing decides whether you get an uplifting effect or a heavy, sedative one — and with this strain the window is narrow. Read the trichomes, not the calendar. Using a jeweller's loupe or a 20–30× USB microscope, inspect the trichomes on the buds themselves (not the sugar leaves, which ripen faster and will mislead you into cutting early):

• Clear: cannabinoids haven't finished developing — too early, effects thin and speedy.
• Milky / cloudy: peak THC and terpene maturity — the sweet spot for most consumers.
• Amber: THC is converting to CBN — more amber means a heavier, more couch-leaning finish.

For Forbidden Glue Auto Feminized, aim for 70–80% milky with 10–20% amber — peak potency and flavour with a touch of sedation, ideal for an after-dinner strain. Want a brighter, more cerebral cut? Harvest earlier, around 60–70% milky with little to no amber. Want maximum body and a deep, heavy finish? Wait for 80–90% milky and 15–25% amber, but don't overshoot — past that point some of the bright limonene character fades. On purple phenotypes the pigmented trichomes get harder to read against the dark calyx, so use pistil browning as a backup signal — when 70–80% of pistils have darkened and curled inward, you're in the window. Check at the same time each day under consistent light, because trichomes can flip from milky to amber in 48 hours at the end. Our deep dive on reading trichomes (clear, cloudy, amber) covers the technique in full.

Forbidden Glue Auto Feminized typically finishes in 56–63 days from seed, but cool, low-light conditions stretch that and warm, bright ones compress it — always confirm with trichomes before you cut. A few extra days of patience here pays back more than almost anything else in the grow.

Common Forbidden Glue Auto Feminized growing problems

The four most common ways a Forbidden Glue Auto Feminized grow goes wrong are bud rot, nutrient burn, heat stress, and over-training. Each one is preventable, and because the autoflower clock leaves no room to recover, prevention beats reaction every time. Catch these early and the plant practically grows itself.

Bud rot (botrytis). This is the big one for any dense indica. Forbidden Glue Auto Feminized's tight, resin-packed colas trap humidity inside, and grey rot can hollow out a bud from the core before you see it on the surface. Keep RH at 40–45% from week 5, run constant airflow through the canopy, and inspect the fattest colas daily in the last fortnight. At the first sign of a wilted or browning sugar leaf poking out of a bud, open it up — if you find grey fuzz, cut that bud out immediately and improve ventilation before it spreads.

Nutrient burn (overfeeding). Autos are small, light feeders, and the most common rookie mistake is feeding them like photoperiod plants. Burnt, clawed, brown leaf tips that creep inward are the tell. Stay at 50% strength early, build up slowly, and back off the moment tips darken — it's far easier to add nutrients than to undo a salt buildup in a compressed timeline.

Heat stress. Above ~28 °C the plant foxtails, airy buds form, and terpenes degrade. Keep the tent in the low-to-mid 20s, raise the light if leaves taco upward, and improve extraction before adding cooling.

Over-training a fast auto. Resist the urge to top, FIM, or run heavy high-stress training on a fast auto — there's no veg time to recover, and you'll just stunt her and lose yield. Gentle LST only, finished by week 4. The whole growing approach for this trait is covered in our autoflowering growing guide.

Can you grow Forbidden Glue Auto Feminized outdoors in Canada?

Yes — Forbidden Glue Auto Feminized is genuinely well suited to outdoor growing across southern Canada, and that's the ruderalis advantage. Because it flowers on age rather than daylength, it doesn't need the long, warm season a photoperiod plant requires, which makes it one of the few strains that reliably finishes in short-season QC, ON, and BC. Breeder data puts outdoor yield at 50–150 g per plant depending on sun, pot size, and care.

The autoflower trait is the key to northern latitudes. A photoperiod plant outdoors won't start flowering until the days shorten in late summer, which in much of Canada leaves too little warm weather to finish before the autumn rains and frost set in. An auto sidesteps that entirely: start seeds indoors in late May or early June, move them out after the last frost, and the plant runs its own 8–9-week clock regardless of daylength. You can even stagger plantings for a rolling harvest through the summer rather than betting everything on one September finish.

A few practicals. Give each plant a 5–10 gallon fabric pot or a well-drained raised bed and the sunniest, most sheltered spot you have — six-plus hours of direct sun is the floor. Watch for the same bud rot risk as indoors: Canadian late-summer dew and rain hit dense colas hard, so a simple rain cover or a covered patio in the final weeks protects the harvest, and good spacing keeps air moving. The bonus is that those cool late-August and September nights often trigger the purple phenotype outdoors with no effort on your part. Browse the full autoflowering strain collection for other short-season options.

Forbidden Glue Auto Feminized vs Gorilla Glue #4

If you know the Glue family, the natural reference point is Gorilla Glue #4 — and PPS carries it, so it's an easy side-by-side. GG4 in its classic form is a photoperiod strain: it flowers in 9–10 weeks, reaches THC around 24%, and can push higher yields, but it needs a managed 12/12 light switch, runs a longer total cycle from seed, and delivers a purer diesel-pine profile with less phenotype variety. It's the proven heavyweight — predictable, potent, and a benchmark for resin.

Forbidden Glue Auto Feminized trades a little ceiling yield for speed and simplicity — 56–63 days from seed with no light-schedule change — and, thanks to the Zkittlez and Lemon in the cross, a brighter, more complex terpene profile plus a real chance at purple buds that classic GG4 rarely throws. The effect is similar in shape — both lean into a heavy, relaxing body finish — but Forbidden Glue Auto Feminized's cerebral, citrus-led onset is more pronounced before the indica lands. Pick GG4 if you want the proven photoperiod heavyweight and you're set up to run a flip; pick Forbidden Glue Auto Feminized if you want flavour variety, faster turnaround, and an autoflower that fits a short Canadian season or a discreet tent.

There's also a phenotype angle that separates the two. Because GG4 is a more stabilised, single-lineage line, a pack runs fairly uniform — what you grow is close to what your neighbour grows. Forbidden Glue Auto Feminized, as a multi-way cross of Zkittlez, GG4, Lemon, and ruderalis, is closer to a small phenotype hunt: one pack can spread from short, bushy, fruit-forward plants with a high chance of purple to taller, branchier, fuel-forward ones that lean on the diesel. Since these are feminized seeds, every plant is female, so no slot is wasted on males and the hunt is purely about expression. Keep notes on each plant — aroma at the stem rub, bud density, trichome coverage, how she handles your environment — pick the phenotype that matches what you want, and run it again from a fresh pack to chase the same character. That selection process is half the appeal for growers who enjoy it, and it's the opposite of what a stabilised heavyweight like GG4 offers. Browse the rest of the autoflowering strain collection or the indica-leaning strains to see where it sits in the lineup.

→ Buy Forbidden Glue Auto Feminized Seeds in Canada — $64.99 a pack, germination guaranteed, free shipping over $150.