Question 1

How often should I water a cannabis plant?

Accepted Answer

It depends on the medium, pot size, stage, temperature, and humidity. In soil, let the top inch dry and the pot lighten before watering again. Coco and hydro follow a wetter rhythm, but the root zone still needs oxygen. Overwatering is more common than underwatering. A quick log of when and how much you water makes the pattern visible.

Question 2

What nutrients should I give my cannabis plant?

Accepted Answer

Vegetative plants need more nitrogen; flowering plants need more phosphorus and potassium. Start conservatively, measure EC or PPM, and adjust by plant response. pH is usually more important than the brand: soil near 6.0–6.8, soilless or hydro near 5.5–6.5. Never feed aggressively on a weak or stressed plant.

Question 3

Why are my cannabis leaves turning yellow?

Accepted Answer

Yellowing can be natural lower-leaf fade late in flower, or it can signal pH lockout, nitrogen deficiency, overwatering, light or heat stress, root problems, or pests. One symptom has many causes. Check the medium, runoff, recent changes, environment, and pest pressure before treating.

Question 4

What temperature and humidity should a cannabis grow room have?

Accepted Answer

Rough targets: seedling 70–80°F / 65–75% RH; veg 75–85°F / 50–65% RH; flower 68–78°F / 45–55% RH. Read these alongside VPD and the cultivar's preferences. Stability matters more than chasing a single number.

Question 5

How do I know when to harvest cannabis?

Accepted Answer

Use trichome color and pistil maturity, not the calendar alone. Clear trichomes are early; milky trichomes are peak for most cultivars; amber trichomes indicate more ripeness and sedation. A jeweler's loupe or handheld microscope is enough.

Question 6

How often should I feed cannabis nutrients?

Accepted Answer

Frequency follows the medium and the plant, not a fixed day count. Soil holds a charge, so many growers alternate feed and plain water. Coco and hydro are inert and are usually fed every watering at a lower strength. What matters more than the interval is consistency plus a record: log strength and date every time, and the pattern that actually works for your room becomes visible. Skip or dilute a feed when a plant is stressed, newly transplanted, or already showing burn.

Question 7

What nutrients do cannabis plants need at each stage?

Accepted Answer

Seedlings need very little — usually just a lightly buffered medium and water. Vegetative growth leans on nitrogen for leaves and stems, with steady calcium and magnesium. Flowering shifts toward phosphorus and potassium while nitrogen tapers. Late flower needs less of everything as the plant finishes. These are directional shifts, not a schedule: cultivar, medium, light intensity, and temperature all move the target, so read the plant alongside the stage.

Question 8

What EC or PPM should I feed, and how do I read runoff?

Accepted Answer

There is no universal ideal number. EC is more useful as a trend than a target: compare what you feed against what comes out. Runoff meaningfully higher than the feed suggests salts are accumulating and the plant is taking up less than you are giving — ease off or water plain. Runoff meaningfully lower suggests heavier uptake and room to feed. Measure the same way every time, because a number is only comparable to your own history. PPM scales differ (500 vs 700), so record which one your meter uses.

Question 9

How do I fix nutrient burn or a nutrient lockout?

Accepted Answer

Nutrient burn usually shows first as crisping or browning leaf tips, often after a strength increase. Stop feeding at that strength, water plain until runoff EC settles, and let new growth tell you whether it worked — scorched tissue does not heal. Lockout is different: the nutrient is present but unavailable, commonly because pH drifted outside roughly 6.0–6.8 in soil or 5.5–6.5 in soilless or hydro. Check pH and runoff EC before adding anything, since feeding more into a lockout makes it worse. Change one variable at a time so you can tell what actually helped.

Question 10

How far should an LED grow light be from cannabis plants?

Accepted Answer

Use the fixture maker's hanging range as a starting point, then verify the canopy rather than treating distance as the dose. Record the distance in inches or centimeters, dimmer setting, plant stage, and a PPFD reading or clearly labeled estimate at several canopy positions. A center reading can hide dim edges or a hot spot. Change height or output gradually and compare new growth before changing something else.

Question 11

What is the difference between PPFD and DLI for cannabis?

Accepted Answer

PPFD is the photosynthetic light reaching a square meter each second at the measurement point, written as micromoles per square meter per second. DLI adds the photoperiod and describes the total delivered across a day, in moles per square meter per day. For a constant PPFD, calculate DLI as PPFD multiplied by light-hours and 3,600, divided by 1,000,000. Both are comparison tools, not universal prescriptions.

Question 12

Do autoflowers need a different light schedule?

Accepted Answer

Autoflowers do not require a 12/12 switch to initiate flowering, but that does not make one long schedule correct for every plant or room. Compare any schedule alongside measured or clearly labeled estimated PPFD, calculated DLI, temperature and humidity, plant stage, energy and heat limits, and the plant's response. Keep the schedule stable long enough to read the result and change one variable at a time.

Question 13

Should I copy a PPFD chart from another cannabis grow?

Accepted Answer

Treat an outside chart as context, not a prescription. Fixture spectrum and geometry, meter or app method, canopy shape, cultivar, stage, carbon dioxide, temperature, irrigation, and nutrition all change the response. Make a small grid at your own canopy, label the source of every value, and keep the same measurement method when you compare a later change.

Question 14

Is bleaching always caused by too much light?

Accepted Answer

No. Bleaching is a visible loss of pigment, not a complete diagnosis. Compare where it appears in the canopy, whether it followed a fixture, dimmer, distance, or schedule change, the PPFD source and map position, temperature and humidity, watering and feeding history, pest pressure, and how the symptom progresses before deciding what to adjust.

Question 15

How can I tell cannabis light stress from heat stress?

Accepted Answer

Possible excess-light patterns are usually strongest in the most exposed canopy area and follow a documented intensity, height, or schedule change. Heat stress needs local temperature, humidity, airflow, and timing evidence and may not follow the light map. The patterns can overlap, so compare exposed and shaded growth, repeat photos, and environmental readings instead of deciding from leaf shape alone.

Question 16

Should I lower my grow light immediately when top leaves look stressed?

Accepted Answer

Address an immediate electrical or unsafe-heat condition first. Otherwise, verify fixture output, distance, canopy measurement source, schedule, local temperature and humidity, and recent root-zone changes before reacting. If a change is warranted, make it measured and reversible, record when it happened, and avoid changing feed, watering, and lighting together.

Question 17

What should I log before adjusting a cannabis grow light?

Accepted Answer

Record fixture and model, dimmer setting, distance in inches or centimeters, photoperiod, canopy position, PPFD source or method, temperature and humidity source and time, plant stage, recent watering or feeding changes, and repeatable photos of affected and unaffected growth. That baseline lets you compare the next light period and the next few days without guessing.

Cannabis plant care FAQ: practical answers with the context to use them safely

Watering is the most common early mistake

Nutrients follow the plant, not the bottle

Environment and observation beat guessing

Treat grow-light distance and schedules as measurements

Harvest timing needs trichome and pistil evidence

Common questions

Evidence and scope

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