Watering Without Drowning It

More first grows die from watering than from anything else. Not from bad light, not from bugs, not from nutrients. From a well meaning person with a watering can.

The reason is that overwatering and underwatering look almost identical from across the room. Both make the leaves droop. If you read droop as thirst, and it was actually too much water, you add more water and the plant gets worse, which reads as more thirst. That loop takes about ten days to kill a seedling.

The fix is not a schedule. It is learning to tell what is actually going on in the pot, and there is a simple physical test that gets you most of the way there.

Stop watering on a schedule#

"Water every three days" is advice that works until it does not. How fast a pot dries depends on plant size, pot size, temperature, humidity, airflow and how much light the plant is getting. A three gallon pot with a seedling might stay damp for eight days. The same pot with a plant in week six of flower might need water every 24 hours.

Water when the pot is ready, not when the calendar is.

The lift test#

Pick the pot up. That is the whole technique, and it is more reliable than any moisture meter under thirty dollars.

To calibrate, do this once. After you water thoroughly and the pot has finished draining, pick it up and remember how heavy that feels. Then, a few days later when the top two inches of soil are dry, pick it up again. The difference is obvious and it is large. A saturated three gallon pot can weigh two to three times what the same pot weighs dry.

Water when the pot feels light. In practice that means the top one to two inches of soil are dry to your knuckle and the pot has lost most of its weight.

You want the soil to go from wet to nearly dry between waterings. That dry back is not neglect, it is part of the cycle. Roots need oxygen, and the only time they get it is when water drains out and air moves into the gaps.

How much to give it#

Once the plant is established, water until you get 10 to 20 percent of what you poured coming out the bottom as runoff.

That means a three gallon pot takes roughly three quarters of a gallon to a full gallon, and you should see a few cups come out the drain holes. Runoff matters because it carries away built up salts from fertilizer and from your tap water. A pot that never gets runoff slowly accumulates salt, and after six weeks that shows up as a deficiency that no amount of feeding fixes.

Pour slowly and evenly across the whole soil surface, not in one spot. Dumping it in the center carves a channel that sends water straight down the middle and leaves the outside dry.

Then dump whatever collected in the saucer. A pot sitting in a tray of standing water is being overwatered continuously no matter how carefully you poured.

Seedlings are the exception to all of this. Water a small ring near the stem, around a cup at a time, and widen it each watering until week three.

Reading the plant#

Symptom	Overwatered	Underwatered
Leaf feel	Firm, thick, almost swollen	Thin, limp, papery
Leaf shape	Curled down hard, clawing	Drooping from the stem, edges soft
Pot weight	Heavy	Light
Soil surface	Dark, damp, sometimes algae or gnats	Dry, pale, pulling from the pot edge
Recovery after water	Gets worse	Visibly better in 2 to 4 hours
Growth rate	Slow, stalled, pale	Slow, but greener

The recovery row is the tiebreaker. An underwatered plant perks up within a couple of hours of a proper drink and looks normal by the next morning. An overwatered plant gets no better, or gets worse.

If you conclude you have been overwatering, the treatment is to stop. Let the pot dry out completely, get a fan blowing across the soil surface, and wait. It may take four or five days. Do not try to help it with more water, nutrients or a transplant.

The water itself#

Tap water is fine for most people in most places. Cannabis is not as fussy about this as forums suggest.

If your city uses chlorine, letting water sit out uncovered for 24 hours will off-gas most of it. If your city uses chloramine, which many now do, sitting out does nothing. Chloramine at municipal levels is not going to kill your plant in soil, so you can either ignore it or run the water through a carbon filter. Do not buy reverse osmosis gear for grow one.

Water temperature should be around 65 to 72F. Cold water out of the tap shocks roots and slows growth for a day. Fill a jug and let it come to room temperature. This also solves the chlorine question for free.

Softened water is the one real exception. Water from a salt based softener carries sodium that builds up in soil and will cause problems. If your house has a softener, use an unsoftened outdoor spigot or buy gallon jugs.

pH matters more than the source. Soil takes up nutrients best between 6.0 and 7.0, with 6.5 being a good middle. Most tap water lands between 7.0 and 8.0 and pre-amended soil buffers a lot of that, which is why plenty of people get away with never checking. But if your plant shows deficiency symptoms while properly fed, pH is the first suspect, not the last.

How much a plant drinks, by stage#

A rough sense of what normal looks like in a three gallon fabric pot:

• Seedling, weeks 1 to 3. A cup or two every three to five days, in a ring.
• Vegetative, weeks 4 to 7. Half to three quarters of a gallon every two to four days.
• Flowering, weeks 8 and on. Three quarters of a gallon to a full gallon every one to three days.

If your plant is drinking dramatically less than this, either the environment is cold or the roots are in trouble. If it is drinking much more, that is usually a good sign, as long as the plant looks healthy.

Get on a rhythm and mostly leave it alone#

Once you have done this for a few weeks, you will stop measuring and just know. Lift the pot in the morning, water or do not, move on with your day.

Watering also interacts with everything else in the tent: hot dry air makes a plant drink faster, and a light hung too close bakes the top of the pot. That is the next thing to set up.