Watering

[Challir17]

My plants are auto flowering northern lights, they are three weeks old from germination to veging. They only inch or two from soil. I'm growing in coco medium. My humidity is low around 40% (one of my problems) there are early signs of heat stress and I don't know exactly how much to water my plants. This is my second grow I'm going 10 plants under 250ww (just changed from 400w today to tackle heat stress)

[SinsemillaScientist]

Id need to know more about your setup to help. Are you in a closet basement grow tent? What about ventilation? And if you have any, try upgrading to a higher cfm rating on your fan. Small circulatory or oscillating fans on low setting can help, is it A/C accesible? For coco is it straight fiber or soil mix/ perlite? And in veg try running an 18/6 schedule with the light off for the hottest 6hrs of the day can help drastically. As far as water goes less is more with small plants but its hard to say without pictures, water P.H. runoff P.H., nutrients etc..

p.s.- you can accomplish great results with 250w of light but with ten plants your looking at each plant getting roughly 25w each. Think of your light as pie and each plant gets an equal piece, (in prime conditions). Again this is all just obtuse feedback based on what i know and my experiences, happy growing!

[D.A.A.S.69]

Hello 17, Great advice from SinsemillaScientist above.
Pictures of your plant would help alot.

[SinsemillaScientist]

https://www.growweedeasy.com/heat-light-stress

This should help too

[Challir17]

Here is my set up. I'm open to constructive criticism so please don't hold back. Temp dial reads 85f humidity reads 50% my set up is in a attic. Straight fibre with the coco. My lights are running 18/6 lights are on through the night. Again please have a look at the set up I have

[NAKEDGARDENER]

Are you just using coco coir?

[Flockshot]

Weigh your plant when the coco is what you consider to be 'bone dry'.

Fully water your plant until you get the desired amount of run off.

Weigh your plant when it is fully watered.

Half way between those weights is the weight you should use to water your plant, in my opinion.

After a short period of time you will recognize that 'light weight' and will no longer need to weigh.

my 2c

[Challir17]

Seems like a logical method. My plants are only 3 weeks old but I wouldn't want to overrated them by using your method would this be the case?

[SinsemillaScientist]

At 85°F, with that much humidity, the heat index of the room sounds to me could be making your girls, (at such a young age) develop slowly and droop or curl, possibly even burn. And I agree with Flockshot his method will give you the most accurate and recordable results, be sure to watch each closely as some may want more or less depending on several factors i.e. strain, phenotype, air movement, temperature etc...Also look into an echaust system you can duct outside, there iss even stealthy ways on GWE to help guide you and most things can be purchased on amazon relatively cheap.

https://www.growweedeasy.com/perfect-marijuana-grow-room

https://www.growweedeasy.com/stealthy-exhaust-systems-for-indoor-plants

https://www.growweedeasy.com/5-secrets-cannabis-heat-control

https://www.growweedeasy.com/exhaust

And those links should get you to where you want to be, good luck and happy growing friend!

[Challir17]

Great information thanks. I have a carbon filter fitted out of the picture I'm not sure how effective it is since my last grow that went sour. So your saying the method above is trustable at such a young age? Many thanks again for your reply

[SinsemillaScientist]

I trust all of gwe ingormation its necer lead me astray yet and there stticles are easy to follow for novice and expert alike

[Weed Pharma]

I would water/feed to the drip line only- as often (every 2 -3 days) when it dries out between 1 knuckle to 2 knuckles (1"-2") and not let it get any lower than that. Water/feed until some water comes out the bottom.
When you grow in coco, it's watered differently than in soil as you treat it like a hydro grow and it needs constant nutrients.

A 250w is fine for that many plants in veg- but 35-50w per plant is used for flowering- so 400w will be on the lower end. (personally, I would cull a few to three, of the ones that dont bounce back or the weakest ones)
Backing the lights off was a good place to start. And adding another fan for circulation would help, along with increasing the exhaust cfm as mentioned.

The plants have roots, so humidity is not at the top, of the list of worries.

[Challir17]

So by filling my 16l pots of coco with lets just say 2l of water with neutriants I will not over water my plants, permitting I have a decent drain off?

[Weed Pharma]

Correct- that's "Drain to waste" -you see on feed schedules.

[NAKEDGARDENER]

It’s my understanding that if you are using just coco then it should never be allowed to dry out, it’s not soil and contains no nutrients other than the buffering, and the nutrients you must use if you have it buffered yourself or it was already buffered. No one seems to pick up on this....

DrPhoton

[NAKEDGARDENER]

How Frequently to Fertigate

There are three main ways to determine your fertigation frequency:

By Look and Feel

The surface of the coco should never get dry! If you are used to growing in soil, you will certainly feel like you are over-watering in coco. When you apply each fertigation, the coco should still be moist from the previous fertigation. If the surface of the coco is dry, fertigation frequency should be increased. If the surface of the coco becomes so dry that it turns lighter brown, the coco is dangerously dry and you are likely burning your plants with high EC.

By Volume of Water Needed

You should fertigate frequently enough that about 5% of container volume of water produces run-off. This is less water than most growers assume. Fertigation quantities are small because frequency is high. Since you are never giving the coco much time to dry out, there is never going to be much capacity for it to hold more. As an example, in 5 gallons of media, it should take about 1 quart of water to achieve adequate run-off. If more than 1.5 quarts are required to produce adequate run-off, fertigation frequency should be increased.

By Monitoring EC

Early in the grow, you should use look and feel along with volume to determine frequencies. However, as the plant becomes established and is growing rapidly, you can also consider EC. As explained below, when the difference between inflow EC and run-off EC becomes too large, increasing fertigation frequency is the preferred way to lower it. Obviously, there are limits to this, but mature plants are difficult to overwater in coco/perlite. See our tutorial, “How to Manage Run-off EC”.

Start with DAILY Fertigation

In coco, your plants should be fertigated at least once per day. It is important that they are always in appropriately sized containers. A specific transplant strategy is laid out in chapter 2. Starting in pint sized containers, small seedlings should be fertigated once per day. Once they move to half-gallon containers and become established, you can begin fertigating twice per day. In final containers, plants may stay at twice per day through the rest of the vegetative period or require 3x daily fertigation depending on container size, climate, lights, and relative humidity. Tracking EC and run-off will allow you to determine when to increase frequency.

During Flowering: At Least Twice Daily

Water needs increase and your fertigation frequency should as well. Plan to increase to 3-5x per day, depending primarily on container size. You can get away with twice daily watering in larger containers. However, in coco, the best results come from small containers with more frequent fertigation.

Fertigation Event Timing:

For timing fertigation events, one hour of “lights on” is equivalent to two hours of “lights off”. Timing for these events works best as I describe in the table below.
Light Cycles and Fertigation Timing:

The light schedule you are using needs to be considered when setting the timing of fertigation events. In the cannabis community, light timing is expressed as a fraction with “Lights on” time over “Lights off” time.

24/0: Lights are on 24 hours and off 0 hours
18/6: Lights are on 18 hours and off 6 hours
12/12: Lights are on 12 hours and off 12 hours. 12/12 timing is used during the flowering period with Photoperiod plants.
Fertigation Event Timing
How to Handle Run-Off

Remove Run-Off Quickly

As run-off emerges from the bottom of the pots, it should be removed as quickly as possible. If pots are allowed to sit in their own run-off, it will be reabsorbed into the coco. When this happens, salts will accumulate in your coco and quickly burn your plants.

I recommend using plant elevators to raise the pots within the saucer. This prevents the re-absorption of run-off and increases drainage and airflow. To remove the waste water from the saucers, I strongly recommend elevating them and installing drain lines. We have complete plans and instructions for making “DIY Self-Draining Saucers”.

Measure the EC of the Run-off

Reliable meters can be purchased for as little as $10-$20. I use this Hone Forest EC meter and I have verified it’s accuracy against other meters. The technology involved is simple and you do not need to invest in an expensive EC meter.

To know how to respond to run-off EC numbers, be sure to read our tutorial “How to Manage Run-off EC”.

Taken from cocoforcanabis. Website.