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.

Posted by GroHaus Cannabis Cultivation Team on Mar 31st 2025

How to Size Cooling & Airflow for Grow Tents

Quick Guide: How to Size Your Cooling & Airflow for Grow Tents

Not sure how much cooling or ventilation your grow tent really needs? This quick guide walks you through exactly how to calculate it — and how to keep your grow space dialed in without guesswork.

Step 1: Calculate Grow Room Volume

Start by measuring the length, width, and height of your grow tent in feet. Multiply them together to get your total volume in cubic feet (ft³).

Example: A 4ft x 4ft x 6.5ft tent = 104 ft³

Step 2: Estimate Your Heat Load in BTUs

Lights, plants, and insulation all add heat. A quick estimate:

Multiply total watts of light by 3.41 (BTU/hr)
Add 25 BTU per plant
Adjust for insulation (1.0 = good, 1.5 = poor)

Use our Grow Room BTU & CFM Calculator to do this instantly.

Step 3: Determine Your CFM (Airflow)

To keep your tent cool and fresh, your fan should replace the air every minute or so. Multiply your room volume by 1.2 for a safe estimate of CFM needed.

Pro tip: Add 20–30% more CFM if you're using filters, ducting turns, or high-output lights.

Recommended Tools

Want to Go Deeper?

Explore our full guide on managing indoor climate, including:

Ideal humidity and temp by growth stage
How heat affects transpiration & yield
Smart automation tips

Read the Full Environment & Climate Guide

Tool & guide by GrōHaus — helping growers dial in their light, space, and yield.