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.

Exhaust Fan Timing Estimator

Airflow. Refresh. Balance. Smarter cultivation starts with smart ventilation.

Exhaust Fan Timing Estimator

Estimate how long it takes to fully exchange the air in your grow room using your fan’s CFM rating.

This tool helps growers calculate how quickly their exhaust fan can replace all the air in a grow room, allowing for properly timed ventilation cycles. It's ideal for setting fan timers, verifying airflow efficiency, and maintaining optimal air quality for plant health.

Room Length (ft): Room Width (ft): Ceiling Height (ft):

Fan Airflow (CFM): ℹ️ More info (CFM Calculator)

Grow Journal

Track your airflow planning and ventilation specs in one place with the Grow Journal.

Learn About the Grow Journal Open Dashboard

How This Works

This calculates how long it takes for your fan to fully exchange the air in your room. This is useful for setting timers or verifying that your fan is powerful enough.

Formula

Exchange Time (minutes) = Room Volume (ft³) ÷ CFM

Example: A 10×8×8 room = 640 ft³. A 200 CFM fan changes the air in ~3.2 minutes.

Tips

Target 30–60 air exchanges per hour in sealed rooms
Use controllers or timers for cycling fans
Add carbon filters to reduce odor without reducing flow too much

Tool by GrōHaus — helping growers ventilate smart, stay fresh, and grow clean.

Exhaust Fan Timing Estimator

Exhaust Fan Timing Estimator

Grow Journal

How This Works

Formula

Tips

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