Starter Kit XL – 6 Bottle Set (576 Ounce Total)

Starter Kit XL

Your complete nutrient system: beyond the basics. 

Starter Kit XL is our most advanced kit, featuring a complete 6-bottle system designed to support strong plant growth and high-quality flower production.

  • Full nutrient system with 6 powerful formulas 
  • Makes 500–600 gallons of ready-to-feed solution 
  • Compatible with soil, coco coir, hydroponic systems, and aquaponics 
  • Trusted by home and weekend gardeners 
  • Clear instructions 

“My garden exploded after the first week.” 
$299.99

Packaging Update: You may receive previous or updated packaging during our transition. Same formula, same performance.

Interested in bulk buying or wholesale pricing? Contact us here.
Starter Kit XL – 6 Bottle Set (576 Ounce Total)
  • Starter Kit XL – 6 Bottle Set (576 Ounce Total)
  • Starter Kit XL – 6 Bottle Set (576 Ounce Total)

Stronger stalks. Bigger yields. The secret is in the system.

Most kits stop at the basics. Starter Kit XL removes the guesswork while covering more ground. Get structure, bloom density, root-zone clarity, and microbial vitality — all working in harmony in one simple, integrated system. No Ph.D required. 

“I’ve never had results like this—ever.”

Complete but customizable: Follow the included schedule or adjust as needed based on your plants’ rhythms and grow goals.

Safe for all plants: Transparent, plant-safe formulas — ideal for herbs, fruit, vegetables, and ornamentals.

Support from seed to harvest: 6 complementary nutrients  forthe entire growth cycle.

Complete but customizable: Follow the included schedule or adjust as needed based on your plants’ rhythms and grow goals.

Safe for all plants: Transparent, plant-safe formulas — ideal for herbs, fruit, vegetables, and ornamentals.

Support from seed to harvest: 6 complementary nutrients  forthe entire growth cycle.
See How It Works

What’s inside?

Starter Kit XL is the next chapter in the Humboldts Secret System Playbook. For the gardeners who want more — this kit includes 6 synergistic formulas for complete support: 

Base A & B (1 Gallon Bundle): The Foundation. Full-spectrum macronutrients including Nitrogen, Phosphorus, Potassium, Calcium, and Magnesium. 

Golden Tree (32 Ounce): The Catalyst. Improves yield quantity and quality with kelp, trace minerals, and simple carbs. 

CalMag & Iron (1 Gallon): The Strengthener. Corrects micronutrient deficiencies and fortifies plant structure. 

Flower Stacker (1 Gallon): The Multiplier. Encourages fuller blooms and dense flower formation. 

Plant Enzymes (32 Ounce): The Purifier. Breaks down dead roots and boosts nutrient uptake. 

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How to use Starter Kit XL

(It’s simple, we promise).

1

Choose your plant stage (seedling, veg, flower)

2

Use the chart to match nutrient amounts to your plant’s needs

3

Always dilute in water — never mix concentrates

4

Water as normal

5

Watch results appear within days
No mystery. No learning curve. Just a proven sequence that works.

Increase yields by 568%.

No myths, just Humboldts Secret. See the proof on screen — in real-world tests, our plant nutrient system boosted yields by over 500%. Imagine what it could do for your garden.

Your plants are begging for more.

Healthy plants need more than macronutrients. Starter Kit XL goes beyond the basics, addressing structure, flavor, bloom, and resilience:  

  • Strengthens stalks and branches to support heavier fruit.  
  • Feeds beneficial microbial life to enhance aroma, density, and the sticky qualities that define a rewarding grow.

Don’t settle for half the story. Your plants will thank you for it. 

"Gave me the flavor and stickiness I could never get from molasses." 

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Visible victories from gardeners like you.
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Customer Feedback

How long does the kit last? And other FAQs.
Is Starter Kit XL good for hydroponic or soil systems?

Starter Kit XL works across all major growing mediums, including hydroponic systems, coco coir, organic soil, aquaponics, raised beds, and even tower gardens. It’s fully compatible and easy to integrate into your current setup.
Do I have to use all 6 bottles every time?

Not necessarily. ​Base A & B and Golden Tree provide the foundation. Additives like CalMag & Iron let you address specific plant needs — like structure, deficiency correction, or bloom enhancement. Gardeners often customize depending on stage and system.
Can I mix everything in one jug?

Yes. All nutrients can be added to the same watering container. Golden rule: Never mix them while concentrated — add each one to the water individually to avoid nutrient lockout and get the best uptake.
What makes Starter Kit XL different from other nutrient kits?

While most kits focus on just the basics, Starter Kit XL offers advanced support for root health, stalk strength, and bloom density — all in one box. You get better results without chasing individual bottles from different brands.
Is this safe for tomatoes, herbs, and vegetables?

Yes, Starter Kit XL is one of our most popular kits for edible gardens. Every product is free of synthetic PGRs and mystery additives, making it a smart choice for fruit trees, berries, greens, herbs, and flowering plants.
How long will it last?

Starter Kit XL makes between 500 and 600 gallons of nutrient solution. That covers multiple cycles for smaller setups or several weeks of feeding in larger gardens.
Is Starter Kit XL beginner-friendly?

Absolutely. The schedule included in Starter Kit XL is clear, the mixing is simple, and the formulas are designed to work together seamlessly. And you can use our Nutrient Calculator to help make things even clearer. Thousands of first-time gardeners say it gave them the confidence to grow again.
What if I don’t see results?

Results matter to us. That’s why we offer a 6-Month Satisfaction Guarantee on purchases up to $250. If your plants aren’t responding, we’ll help troubleshoot or refund your purchase.

Unlock the next tier of growth.

Tens of thousands of gardeners trust Starter Kit XL — because it works. Get everything you need in one box, thoughtfully formulated and clearly explained to unlock your garden’s hidden potential for bigger, better results.

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