How to grow Alpha 21
- Breeder: Herbies
- Genetics: Mostly Sativa
- THC: up to 30%
- Type: Photoperiod, feminized seeds
- Difficulty: moderate
- Flowering: about 7 to 9 weeks
- Flavors: earthy, sweet, spicy, citrus
Alpha 21 (Totally Alpha OG x Haze IBL x Zalla) is a Sativa-dominant medical strain at 30% THC giving potent full-body relaxation that relieves pain and aids sleep.
What is specific about Alpha 21
- Sativa-leaning, expect a big stretch when flowering starts; top early or run a net (ScrOG).
- Rewards strong light and steady feeding with heavy yields.
- Very high THC, nutrient-hungry in flower; ramp feeding gradually and watch for tip burn.
Indoor calendar for Alpha 21
| Stage | When | Note |
|---|---|---|
| Germination | week 1 | Warm, humid and dark until the sprout shows. |
| Seedling | weeks 2 to 3 | Gentle light on 18/6. |
| Vegetative | weeks 4 to 7 (you decide) | Three to six weeks on 18/6; longer growth means a bigger plant. |
| Flowering | 7 to 9 weeks after the switch to 12/12 | Expect the plant to stretch in the first two to three weeks. |
| Harvest | around week 14 to 18 | Depends on how long you let it grow first. |
| Dry and cure | three to four weeks more | One to two weeks drying, then at least two weeks curing in jars. |
About 17 to 22 weeks from seed to cured buds, with 7 to 9 weeks of flowering.
Week by week
Germination: Days 1–7
Pop the seed.
- Soak in a moist paper towel or plant 1cm deep in light, airy soil.
- Keep warm (22–25°C), humid and dark until the sprout appears.
- Moist, never soggy.
Seedling: Weeks 2–3
First true leaves.
- Gentle light on 18/6, high humidity (~65%).
- Tiny waterings near the stem; let the top dry between.
- Quarter-strength nutrients at most.
Vegetative: Weeks 4–7 (you control length)
Build the plant.
- Photoperiod: keep 18/6 as long as you want size, then flip to 12/12 to begin flowering.
- Feed grow (high-N) nutrients; train (LST/topping) for an even canopy.
- Sativa-leaning: leggier, give vertical room.
Flowering: ~7–9 weeks of bloom
Buds bulk up.
- Now on 12/12. Expect a 2–3 week stretch early, give headroom.
- Switch to bloom (high-P/K) nutrients; lower humidity (~45%) to prevent bud rot.
- Watch trichomes: mostly cloudy with some amber = peak ripeness.
Flush & harvest: Final 1–2 weeks
Finish clean.
- Plain water (no nutrients) the last 1–2 weeks for a smoother smoke.
- Harvest, wet-trim, dry slowly (~60°F / 60% RH, 7–14 days).
- Cure in jars 2+ weeks, burping daily at first.
~14–17 weeks (plus veg time).
Growing Alpha 21 outdoors
Outdoors in central Europe photoperiod plants start flowering in early to mid August, so Alpha 21, with 7 to 9 weeks of flowering, is usually ready in mid September to mid October. That is late in the season: autumn rain and cold bring bud rot, so it suits a greenhouse, a dry southern spot or an indoor grow better than an open northern garden.
Drying and curing
Its sweet and citrus notes come from the most volatile terpenes, the first to go in a warm, fast dry. Dry slowly around 18 °C and 60% humidity for 10 to 14 days and cure in jars to keep them.
How Alpha 21 compares
At 7 to 9 weeks it finishes faster than 70% of the 98 photoperiod strains in our guides (typical: 8.5 weeks).
Its THC, up to 30%, is above the typical 20% for these photoperiod strains.
Bred by Herbies, one of 50 Herbies strains with a grow guide here.
| Similar strain | Flowering | THC | Breeder |
|---|---|---|---|
| CBD Mazar | 8 weeks | 5% | Dutch Passion |
| Crystal White Kush | 7 to 9 weeks | 20% | Dutch Passion |
| Master Kush | 8 weeks | 20% | Dutch Passion |
| White Widow | 7 to 9 weeks | 20% | Dutch Passion |
Effects
sleep, pain relief, euphoric
Grower verdict: 4 reviews, average 5/5.
Questions
Is Alpha 21 easy to grow?
Alpha 21 is considered moderate to grow. This read draws on 4 grower reviews.
When is Alpha 21 ready outdoors?
Outdoors in central Europe photoperiod plants start flowering in early to mid August, so Alpha 21, with 7 to 9 weeks of flowering, is usually ready in mid September to mid October. That is late in the season: autumn rain and cold bring bud rot, so it suits a greenhouse, a dry southern spot or an indoor grow better than an open northern garden.
How strong is Alpha 21?
The breeder lists up to 30% THC. Real results depend on light, feeding and harvest timing.
When should I switch Alpha 21 to 12/12?
When the plant is about half the final height you want: it can double in size during the first weeks of flowering. Flowering then takes about 7 to 9 weeks.
Grow Alpha 21 with me on Telegram: what to do each week, a weekly check in, photo diagnosis and harvest timing. Free, no account.
Track this grow week by week on WeedYouGrow, free, no login.
Something looks wrong? Find your plant problem.
Need the seeds? Find Alpha 21 seeds on SeedYouLike.