How often should I water my weed plant?

Not on a schedule. Water when the pot has lost about half the weight it gained at the last watering, which you check by lifting it. As a starting baseline that works out to every 2 to 4 days in a bagged potting soil, every 1 to 3 days in a peat and perlite mix, and daily in coco coir once the plant is established. The interval shortens as the plant grows and lengthens again in late flower.

How much water does a cannabis plant need per watering?

Roughly a quarter to a third of the pot's volume, if you have let it dry back properly first. On a 5 gallon (19 L) pot that is about 1.2 to 1.6 gallons (4.5 to 6 L). That is more than most guides suggest because it pairs with watering less often - the two numbers move together. The check is the pot's weight afterward: it should come back to what it weighed after the last full watering.

How do I know if my cannabis plant is overwatered or underwatered?

Lift the pot. Both problems make a plant droop, so the leaves alone will not settle it, but the pot's weight will. Droop plus a heavy pot is overwatering. Droop plus a light pot is underwatering. Overwatered leaves feel firm and thick and curl downward; underwatered leaves are thin and papery and recover within an hour or two of a drink.

Can you overwater cannabis in a fabric pot?

Yes, but it is much harder. A fabric pot loses water through its walls as well as its surface, and a nursery trial by Million and Yeager measured a genuinely higher irrigation demand for fabric than for plastic. That faster dry-back is exactly what makes overwatering difficult. You can still do it by watering a tiny plant in a large pot, or by leaving the pot standing in its own runoff so it wicks back up.

Should I water cannabis every day?

Only in coco coir or another fast-draining medium with an established plant, where daily is normal and correct. In a bagged potting soil, daily watering will keep the root zone permanently saturated and suffocate the roots. The medium decides, not the calendar. If you are watering a soil pot daily and it never gets light, that is the definition of overwatering.

Why is my cannabis plant drooping after I watered it?

Almost always because it was already too wet. Droop in a heavy pot is oxygen starvation, not thirst - the pores that should hold air are full of water and the roots cannot respire. The treatment is to do nothing at all: no more water, no feed, no repotting. Wait until the pot is genuinely light, get some air moving over the surface, and check the pot is not sitting in its own runoff.

Does letting cannabis dry out increase potency?

A controlled drought can, in a lab. Caplan, Dixon and Zheng withheld water in week 7 of flower until plant water potential hit about -1.5 MPa, which took 11 days, and got 12 to 13 percent higher THCA and CBDA concentrations. But Morgan's group found severe drought cut both yield and cannabinoid content. The window is narrow and the trial's control was an instrument you do not own. We do not recommend trying it deliberately.

How much runoff should I get when watering cannabis?

It depends on who is feeding the plant. In coco, rockwool or any medium you feed with bottled nutrients, aim for 15 to 20 percent runoff every watering to carry accumulated salts out. In a pre-charged bagged soil, an amended soil or a living soil, aim for damp all the way through with little or no runoff, because what runs out is the nutrient charge you paid for. A diagnostic runoff test is different and needs at least 20 percent.

Is Fox Farm Ocean Forest or a similar pre-charged soil harder to water?

It is more forgiving on frequency and less forgiving on runoff. A pre-charged bagged soil holds a lot of water, so you water every 2 to 4 days rather than daily, and it feeds the plant itself for roughly the first three to four weeks. That is the trade: give it plain water and very little runoff during that window, because heavy runoff washes out the charge you bought. Our soil guide covers reading a bag properly.

Are self-watering pots or systems like Blumat and AutoPot good for cannabis?

They are genuinely good at the problem they solve, which is not being there. If you travel, or you cannot water daily in coco, they beat a plant that goes four days dry. The trade is that they hold moisture steady, and the wet-dry cycle is how the root zone gets its air back. Size them so the pot still dries between fills, or run a coarse, high-perlite medium that keeps its air even when wet.

Do I need to let tap water sit out before watering cannabis?

No. Tap water is fine for container cannabis and standing it overnight does not help. Standing off-gasses free chlorine, which container plants tolerate at tap levels anyway, and most utilities use chloramine, which does not off-gas at all. If you run a living soil and your water report shows chloramine, a carbon filter or a conditioner is the only thing that works. Our planting guide owns the water chemistry.

How often should I water cannabis seedlings?

Water the starter cup to runoff before you plant, then leave it alone until it feels noticeably lighter, usually 7 to 10 days. After that, small volumes whenever the cup feels light, keeping the medium damp but never wet. A seedling has almost no root system and cannot drink down a large volume, which is why starting one directly in a big pot is such a reliable way to drown it. When the cup dries out in 24 hours or less, that is not a watering problem - it is the cue to transplant.

Should I water more or less during flowering?

More during the stretch, then less. Demand peaks in flower weeks 1 to 3 as the plant adds most of its final size, and that is where people underwater. It falls again in late flower, once growth stops and the older leaves start to fade, typically every 1 to 3 days mid-flower stretching to every 3 to 5 days near the end. Keeping the mid-flower rhythm through the final weeks is the most common overwatering of the whole grow.

What time of day should I water cannabis?

At lights-on, or early in the light period. The plant does its drinking and its growing while the lights are on, so water given then gets used rather than sitting in a saturated, unlit root zone all night. Outdoors the same logic makes morning the best time. Watering right before lights-off is the least useful moment and the one most likely to leave the pot too wet for too long.

Guide de culture BudTrainer

À quelle fréquence arroser le cannabis : fiez-vous au pot, pas au calendrier

par {{ author }} Henrique Dias

A gray metal watering can pouring a thin stream of water onto a young cannabis plant in a black fabric grow pot with handles, standing on a wooden surface against a plain cream wall.

Dans cet article

Par Henrique Dias, PDG et cofondateur de BudTrainer
Dernière mise à jour septembre 2026 · 18 min de lecture

Réponse rapide : Arrêtez d'arroser selon un calendrier. Arrosez lorsque le pot a perdu environ la moitié du poids qu'il avait gagné lors du dernier arrosage, ce qui, en pratique, correspond à tous les 2 à 4 jours dans un terreau en sac, tous les 1 à 3 jours dans un mélange de tourbe et de perlite, et quotidiennement dans de la fibre de coco une fois que la plante est bien établie. Voici ce que presque personne ne dit à voix haute : vous arrosez probablement trop souvent. Lorsque nous avons demandé à 387 cultivateurs amateurs de nommer leur plus grande erreur lors de leur première culture, l'arrosage inadéquat est arrivé en tête, et l'excès d'arrosage l'emportait sur le manque d'arrosage d'environ trois contre un. Les recherches pointent dans la même direction. Le groupe de Wayne Morgan a maintenu du chanvre à 30 à 50 pour cent de sa capacité au champ pendant toute une saison et a récolté le même rendement, avec les mêmes niveaux de THC et de CBD, avec deux tiers de l'eau habituelle. L'essai d'irrigation de Richard Roseberg a révélé qu'arroser au-delà d'environ 80 pour cent de ce que la culture pouvait évaporer n'apportait aucun cannabinoïde supplémentaire. La plante ne demande pas un calendrier. Elle vous demande de soulever le pot.

Les mains d'un cultivateur inclinant un arrosoir gris à long bec au-dessus d'un pot de culture en tissu noir dans une tente de culture, un filet d'eau clair atterrissant sur la surface brune claire de tourbe et de perlite et l'assombrissant autour de la tige d'une jeune plante de cannabis en bonne santé.

La réponse courte : À quelle fréquence arroser le cannabis

Si vous voulez un chiffre de base avant d'apprendre à « lire » le pot, le voici. Le substrat définit l'intervalle de base, et la taille de la plante ainsi que votre espace de culture le font varier.

Substrat de culture	Arroser environ tous les	Drainage visé	Facteurs de variation
Terreau de qualité en sac	2 à 4 jours	Peu ou pas tant que le terreau contient encore des nutriments	Plus lent dans une pièce fraîche, plus rapide une fois que la canopée remplit le pot