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 Build a Cannabis Nutrient Schedule (Soil or Hydro)

Feeding your plants the right nutrients at the right time is one of the most powerful ways to boost yield, flavor, and overall health. Whether you're growing in soil or hydroponics, this guide will help you build a feeding schedule that matches your grow style.

What Is a Nutrient Schedule?

A nutrient schedule tells you:

Which products to feed (base nutrients, CalMag, bloom boosters, etc.)
How much to use (measured in tsp/gal or mL/L)
When to feed (by week or plant stage)

Good schedules are based on plant biology—not just the calendar. The best growers adjust based on how the plants look and respond. Read our full Cannabis Nutrients Guide to learn how each nutrient works and what your plants need at every stage.

Soil vs Hydro: What Changes?

Soil: Feed every other watering. Soil buffers pH and holds nutrients longer.
Hydroponics: Feed daily or continuously. Nutrients must be dialed in precisely.

No matter which you use, always monitor EC/PPM, pH, and plant response.

Sample Weekly Feeding Schedule

Here's a basic example for photoperiod plants using a 12-week grow cycle:

Week	Stage	Base Nutrients	Additives
1	Seedling	Water only	Optional root booster
2–4	Veg	Grow A + B	CalMag
5–6	Transition	Grow + Bloom	Silica, enzymes
7–9	Flower	Bloom A + B	PK booster (e.g. Beastie Bloomz)
10–11	Late flower	Bloom	Ripener (e.g. Cha Ching)
12	Flush	Water only	-

This is just a starting point. Always adjust based on your strain, environment, and grow medium.

Autoflowers vs Photoperiods

Autoflowers enter flower automatically (usually week 4–5), so your nutrient schedule must shift earlier. They also prefer lighter feeding—start at 50% strength and increase only if needed.

Common Mistakes to Avoid

Feeding too early (wait until 3–4 nodes)
Mixing nutrients in the wrong order
Not checking pH and EC regularly
Using hard tap water without adjusting

Next Steps

Feeding doesn’t have to be complicated—especially when you’ve got tools to help.

Build Your Feeding Schedule Now

Learn More About Cannabis Nutrients

Tool & guide by GrōHaus — helping growers unlock the potential of every plant.