How to Grow Autoflowers with Cronk's Classic 3-Part (Micro + Grow + Bloom)Updated an hour ago

If you already own Cronk's Classic 3-Part system (Micro, Grow, and Bloom), you have everything you need to grow autoflowers from seed to harvest. You don't need a separate product line, special formulas, or autoflower-specific nutrients. The same three bottles that crush it in photoperiod grows work beautifully with autos — you just need to adjust the schedule.

This guide gives you week-by-week feeding charts at three levels (novice, intermediate, and expert), the correct mixing order to avoid calcium lockout, medium-specific tips for soil, coco, and hydro, and a side-by-side comparison with General Hydroponics Flora Series.

What Makes Autoflowers Different?

Autoflowers don't rely on light schedule changes to trigger flowering. They flower based on age, typically starting around weeks 3-4 regardless of your light cycle. This means:

• Shorter life cycle: 8-12 weeks seed to harvest (vs 14-20+ for photos)
• Lighter feeding: Start at 25-50% strength, build up gradually
• Earlier bloom transition: Switch to bloom-heavy ratios as soon as you see pistils
• Less room for error: No time to recover from major mistakes in a 10-week cycle

The Classic 3-Part handles all of this. Micro provides your base micronutrients and calcium. Grow delivers nitrogen for vegetative development. Bloom supplies phosphorus and potassium for flower production. By adjusting the ratio of Grow to Bloom across the cycle, you match the plant's changing needs perfectly.

The 3-Part Feed Charts

Novice Schedule (3 Products: Micro + Grow + Bloom)

Week	Stage	Micro (mL/gal)	Grow (mL/gal)	Bloom (mL/gal)	EC Target
1	Seedling	1.25	1.25	0	0.4-0.6
2	Early Veg	2.5	2.5	0.5	0.8-1.0
3	Veg / Pre-Flower	2.5	2.5	1.25	1.0-1.2
4	Transition	2.5	1.25	2.5	1.2-1.4
5	Early Flower	2.5	0.5	3.75	1.4-1.6
6	Mid Flower	2.5	0.5	3.75	1.4-1.6
7	Peak Flower	2.5	0	5.0	1.4-1.6
8	Late Flower	1.25	0	3.75	1.0-1.2
9	Ripen	0.5	0	2.5	0.6-0.8
10	Flush	0	0	0	0

Intermediate adds CalMag (2.5 mL/gal throughout, essential for coco) and Bud Booster (1.25-2.5 mL/gal during weeks 4-8 for enhanced phosphorus and potassium).

Expert adds Sticky Bandit (1.25 mL/gal weeks 3-8 for terpene production) and Monkey Juice (2.5 mL/gal throughout for beneficial microbes and root health).

Mixing Order: This Is Where Most People Mess Up

The number one mistake with any 3-part system is mixing in the wrong order. Here's why it matters and exactly how to do it:

1. Silica (if using) — always first, stir thoroughly
2. CalMag (if using) — second, stir
3. Micro — ALWAYS before Grow or Bloom. Micro contains calcium. If calcium meets the concentrated phosphorus in Bloom before being diluted, it forms calcium phosphate precipitate and becomes permanently unavailable to your plants.
4. Grow — after Micro is fully mixed
5. Bloom — after Grow is mixed
6. Additives (Bud Booster, Sticky Bandit) — after base nutrients
7. pH adjust — after everything is mixed
8. Monkey Juice — always last (beneficial bacteria, don't want to stress them with concentrated nutrients)

Key rule: Never let Micro and Bloom mix in concentrated form. Always dilute Micro first, stir, then add the others.

Cronk Classic 3-Part vs. General Hydroponics Flora Series

If you're coming from General Hydroponics Flora Series, the transition is straightforward. The NPK ratios are nearly identical:

Product	Cronk NPK	GH Flora NPK
Micro	5-0-1	5-0-1
Grow	2-1-6	2-1-6
Bloom	0-5-4	0-5-4

Same ratios, same mixing approach. The difference is Cronk is formulated specifically for cannabis with optimized micronutrient profiles and chelation for better uptake in the pH ranges cannabis prefers (5.8-6.5).

Growing Medium Tips

Soil: Most forgiving medium. Start at 50% of the chart values for the first 2-3 weeks since soil has its own nutrient charge. Buffer is high so pH swings are less dangerous.

Coco Coir: CalMag is mandatory, not optional. Coco naturally binds calcium and magnesium. Without supplementing, your plants will show deficiencies even with a full feed schedule. Water to 15-20% runoff every feeding.

Hydro / DWC: Use 50-75% of the drain-to-waste dosages. Change reservoir every 7 days. Monitor EC and pH daily. Dissolved oxygen is critical — use air stones.

Common Autoflower Mistakes

• Overfeeding early: Seedlings need almost nothing. Weeks 1-2 should be very light. More growers kill autos with too much food than too little.
• Missing the bloom transition: Watch for pistils around week 3-4. As soon as you see them, start shifting the Grow:Bloom ratio toward bloom-heavy.
• Not flushing: Give your plants 7-10 days of plain water before harvest. This lets the plant use up stored nutrients and improves the final taste and burn.
• Wrong pH: Soil: 6.2-6.5. Coco: 5.8-6.2. Hydro: 5.5-6.0. Outside these ranges, nutrients lock out no matter how perfect your feeding schedule is.
• Mixing Micro after Bloom: Causes calcium precipitation. Always Micro first.

FAQ

Can I use the Classic 3-Part for both photos and autos?
Yes. Same bottles, just different schedules. Photos get a longer veg period with higher Grow ratios. Autos transition faster.

Do I need CalMag with the Classic 3-Part?
In coco, absolutely. In soil, usually not unless you're using RO or soft water. In hydro, recommended.

What's the difference between the 3-Part and the Prema line?
The 3-Part gives you full control over the Grow:Bloom ratio week by week. Prema is a simplified all-in-one designed specifically for autoflowers. Both work great — it's about how much control you want.

How do I know if I'm overfeeding?
Burnt leaf tips (nutrient burn) are the first sign. If you see them, back off by 25%. It's easier to add more than to fix toxicity.