What is fertilizer, and why do cannabis plants need it?

Fertilizer provides essential nutrients like nitrogen, phosphorus, and potassium to help cannabis plants grow strong, healthy, and produce high yields. In most grow setups, regular feeding is required to avoid deficiencies and promote optimal growth.

What nutrients are essential for healthy cannabis growth?

Cannabis needs macronutrients like nitrogen, phosphorus, and potassium, plus secondary nutrients like calcium, magnesium, and sulfur. Micronutrients such as iron, zinc, and boron are also vital for plant health and development.

When should I start feeding cannabis plants nutrients?

Start feeding once your cannabis seedlings develop their first true leaves. In coco or hydro, feeding may begin as early as day 7–10. In soil, wait until the plant shows signs of slowed growth or pale lower leaves.

What do NPK values mean on cannabis fertilizer?

NPK stands for Nitrogen (N), Phosphorus (P), and Potassium (K), the three primary macronutrients. Ratios like 3-1-2 or 1-4-5 guide what stage of growth the fertilizer supports—veg or bloom.

How do I know if my cannabis plant is overfed or underfed?

Check the EC/PPM of your runoff water. If it's much higher than your input, nutrients are building up—overfeeding. If it's much lower, your plant may be hungry—underfeeding.

Dehumidifier Sizing Tool

Humidity. Balance. Control. Smarter cultivation starts with dialing in your air.

Dehumidifier Sizing Tool

Estimate the right dehumidifier size (in pints/day) for your grow space based on plant count and stage.

Number of Plants: Growth Stage: ? Light Hours Per Day: ?

Grow Journal

Track your humidity control planning and environment data all in one place.

Learn About the Grow Journal Open Dashboard

How This Works

This calculator estimates the amount of water released by plants daily and converts it into pints/day for dehumidifier sizing. Plants transpire more as they grow larger, especially during the flowering stage.

Formula

Water (gal/day) = Plants × Gallons per Stage × (Light Hours ÷ 24)

Pints/day = Gallons × 8 (conversion)

Example

6 plants × 0.5 gal × (18 ÷ 24) = 2.25 gal/day → 18 pints/day

Tips

Size 10–20% higher than calculated to compensate for nighttime RH
Use multiple units for large or multi-zone rooms
Pair with a controller or humidistat for best results

Tool by GrōHaus — helping growers master moisture, airflow, and precision humidity control.

Dehumidifier Sizing Tool

Dehumidifier Sizing Tool

Grow Journal

How This Works

Formula

Example

Tips

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