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Cannabis & Hydroponic Grow Room Guides

Practical VPD, pH, EC, temperature, humidity, CO₂, and DLI guides — written for cannabis and hydroponic growers who want better data and bigger yields.

Getting Started with GrowAI

Set up your first farm, connect hubs, and start viewing live room metrics.

Basics
  • Create farms & rooms
  • Pair sensors to hubs
  • Watch live metrics

Cannabis VPD Chart & Guide — Ideal VPD by Growth Stage

Ideal VPD ranges for cannabis seedling, veg, and flowering stages. Live VPD calculator and stage-by-stage targets.

VPD
  • VPD by growth stage chart
  • Seedling 0.4–0.8 kPa | Veg 0.8–1.2 kPa | Flower 1.0–1.5 kPa
  • How to fix high or low VPD
Read VPD Guide →

Cannabis Grow Room Temperature Guide by Growth Stage

Ideal temperature ranges for cannabis seedling, veg, and flowering stages — day and night targets.

Climate
  • Stage-by-stage temperature chart
  • Lights-on vs lights-off targets
  • Overheating fixes
Read Temp Guide →

Cannabis Humidity Guide — RH% by Growth Stage

Optimal RH% for cannabis seedling, veg, and flowering. How to avoid mold, bud rot, and humidity swings.

Climate
  • Seedling 70–80% | Veg 50–70% | Flower 40–50%
  • Preventing bud rot and powdery mildew
  • Dehumidifier scheduling tips
Read Humidity Guide →

Cannabis pH Guide — Ideal pH for Every Growth Stage

Optimal pH ranges for cannabis in soil, coco, and hydro — by growth stage. What happens when pH drifts.

Nutrients
  • Soil 6.0–7.0 | Hydro/Coco 5.5–6.5
  • pH lockout symptoms by nutrient
  • Daily pH management tips
Read pH Guide →

Cannabis EC & Nutrient Guide — EC/TDS by Growth Stage

Ideal EC and TDS targets for cannabis at every stage — seedling through flush. Avoid nutrient burn and deficiency.

Nutrients
  • Seedling 0.4–0.8 | Veg 1.2–1.8 | Flower 1.6–2.2 EC
  • Signs of nutrient burn vs deficiency
  • Flush EC targets
Read EC Guide →

Hydroponic Growing FAQ

What is the ideal temperature for a hydroponic grow room? +
The ideal temperature for most hydroponic plants is 65–80°F (18–27°C) during the light period and 60–70°F (15–21°C) during the dark period. Seedlings and clones prefer the warmer end (75–80°F), while flowering plants perform best at 68–75°F. Temperatures above 85°F slow growth and increase the risk of root disease, while temperatures below 60°F can stunt nutrient uptake. GrowAI's temperature sensors provide real-time alerts the moment your room drifts outside your set range.
What humidity level is best for hydroponic growing? +
Optimal humidity depends on the growth stage. Seedlings/clones: 70–80% RH. Vegetative stage: 50–70% RH. Flowering stage: 40–50% RH. Late flower / harvest: 35–45% RH. High humidity in flowering encourages mold and bud rot, so a dehumidifier is essential. GrowAI's humidity sensors and trend graphs make it easy to catch swings before they damage your crop.
What is the optimal CO₂ level for a grow room? +
Ambient CO₂ is approximately 400 ppm. Most hydroponic plants grow well between 800–1,200 ppm, with maximum benefit from CO₂ supplementation at 1,200–1,500 ppm — provided temperature and light intensity are also elevated. Above 1,500 ppm offers minimal additional benefit and can be wasteful. CO₂ enrichment is only effective when lights are on; shut off CO₂ injection during the dark period. GrowAI sensors track CO₂ in real time so you never over- or under-supplement.
What pH should my hydroponic nutrient solution be? +
The ideal pH for most hydroponic systems is 5.5–6.5, with 5.8–6.2 being the sweet spot for nutrient availability. Different nutrients are absorbed most efficiently at different pH levels, so keeping pH in range ensures your plants can take up everything they need. pH below 5.5 can lock out calcium and magnesium; above 6.5 iron and manganese become unavailable. Check and adjust daily, or use GrowAI pH sensors for continuous monitoring.
What is DLI and why does it matter for hydroponics? +
Daily Light Integral (DLI) measures the total amount of photosynthetically active light a plant receives over a full day, expressed in mol/m²/day. It combines light intensity (PPFD) with photoperiod duration. Leafy greens grow well at 12–20 DLI; fruiting crops like tomatoes and peppers need 25–40 DLI. DLI is a more accurate metric than lux alone because it accounts for how long the lights are on. GrowAI calculates and displays running DLI in the dashboard so you can dial in your lighting schedule precisely.
How do I monitor my hydroponic grow room remotely? +
GrowAI uses wireless sensors paired to a hub inside your grow room. The hub sends live telemetry to the cloud, and you can view all readings — temperature, humidity, CO₂, light, pH, and moisture — from any device via the GrowAI dashboard. You also receive instant push and email alerts when any parameter drifts out of your defined range, letting you respond to problems even when you're not on-site.

Fruits & Vegetable Grow Guides

Exact pH, EC, temperature, humidity, DLI, and VPD targets for the most popular hydroponic fruits, vegetables, and herbs — from seedling to harvest.

Vegetables
Tomatoes
pH 5.8–6.3 · EC 1.0–4.5 · DLI 20–30
Vegetables
Lettuce
pH 5.5–6.5 · EC 0.8–2.0 · Harvest 28–60 days
Vegetables
Spinach
pH 6.0–7.0 · EC 1.2–2.2 · Temp 50–70°F
Vegetables
Bell Peppers
pH 5.5–6.5 · EC 2.0–3.5 · DLI 20–30
Vegetables
Cucumbers
pH 5.5–6.0 · EC 1.7–3.5 · Harvest 50–65 days
Vegetables
Kale
pH 5.5–6.5 · EC 1.5–2.5 · DLI 12–20
Vegetables
Swiss Chard
pH 6.0–7.0 · EC 1.5–2.5 · DLI 12–18
Vegetables
Arugula
pH 6.0–7.0 · EC 1.2–1.8 · Harvest 21–35 days
Vegetables
Green Beans
pH 6.0–6.5 · EC 1.5–2.5 · DLI 18–25
Vegetables
Radishes
pH 6.0–7.0 · EC 1.2–2.0 · Harvest 22–35 days
Vegetables
Beets
pH 6.0–7.0 · EC 1.6–2.5 · DLI 15–20
Vegetables
Snap Peas
pH 6.0–7.0 · EC 1.5–2.5 · Temp 55–70°F
Vegetables
Zucchini
pH 5.5–6.5 · EC 1.8–3.0 · DLI 20–30
Vegetables
Eggplant
pH 5.5–6.5 · EC 2.0–3.5 · Temp 75–85°F
Vegetables
Bok Choy
pH 6.0–7.0 · EC 1.2–2.0 · Harvest 30–70 days
Fruits
Strawberries
pH 5.5–6.5 · EC 1.2–2.0 · DLI 15–25
Herbs
Basil
pH 5.5–6.5 · EC 1.0–2.5 · Temp 70–85°F
Herbs
Mint
pH 6.0–7.0 · EC 1.4–2.2 · DLI 10–16
Herbs
Cilantro
pH 6.0–6.7 · EC 1.2–1.8 · Temp 50–70°F
Herbs
Chives
pH 6.0–7.0 · EC 1.4–2.2 · DLI 10–16
Herbs
Parsley
pH 6.0–7.0 · EC 1.2–2.5 · DLI 10–16
Herbs
Green Onions
pH 6.0–7.0 · EC 1.4–2.2 · Harvest 10–80 days
Herbs
Watercress
pH 6.5–7.5 · EC 0.8–1.8 · Temp 50–68°F
Herbs
Celery
pH 6.0–7.0 · EC 1.8–3.0 · DLI 14–20
Microgreens
Microgreens
pH 5.5–6.5 · EC 0.8–1.6 · Harvest 7–21 days
View All 31 Growing Guides →

Equipment Guides & Free Tools

In-depth guides for every piece of equipment in your grow room — plus free interactive calculators.

Free Tool

VPD Calculator

Enter temp & humidity to instantly calculate VPD. Interactive heatmap & stage targets.

VPD · Leaf VPD · Heatmap · kPa
 Free Tool

EC to PPM Calculator

Convert EC to PPM using 500 or 700 scale. Includes nutrient target charts for every plant and stage.

EC · PPM · TDS · 500 Scale · 700 Scale
 BOFU

Best Grow Room Monitor

7-parameter monitoring system review. USA, Canada & UK availability. Compare vs Pulse, TrolMaster.

VPD · CO₂ · pH · EC · Temperature
 Equipment

LED Grow Lights Guide

PPFD, DLI, spectrum explained. How to choose between quantum board, bar LED, and COB.

PPFD · DLI · Spectrum · Quantum Board
 Equipment

Grow Tent Setup Guide

Complete grow tent build checklist. Sizing, ventilation, lighting, and environment setup for 2×2 to 10×10.

2×2 · 4×4 · 4×8 · Fan · Filter · LED
 Equipment

Grow Room Ventilation Guide

CFM calculator, inline fans, carbon filters, negative pressure, ducting. Complete airflow guide.

CFM · Inline Fan · Carbon Filter · Duct
 Equipment

Hydroponic Nutrients Guide

NPK explained, EC/PPM feeding charts, pH interaction, deficiency diagnosis, and week-by-week schedules.

NPK · EC · PPM · pH · Deficiency