How tall in veg under a 400HPS and a 6ooHPS before flower????

How tall should I let my plant get before I flower them, to get a good yield? 3 of them (female seeds grapefruit) are 23 inches and 6 of them are 16 inches.

It depends how tall your ceiling is and the amount of light on the side; but generally plants will stretch 100% to 200% once you switch to bloom.
So typicaly a 26 inch tall plant will be 50 to 60 inches tall two to three weeks after flipping.

I'm growing a couple now that easily stretched 300%; so the rule is only general in nature.

If 50 to 60 inches tall is too tall for your area look up LST, which stands for Low Stress Training.

be aware a plant can double to tripple in size during flowering. plants should stay 28-30 in from an air cooled 600w hps....the bigger the plant the more it yields... it kinda depend on the space ur working with...if u have an 8 foot roof id say flower now

FatMarty said:

It depends how tall your ceiling is and the amount of light on the side; but generally plants will stretch 100% to 200% once you switch to bloom.
So typicaly a 26 inch tall plant will be 50 to 60 inches tall two to three weeks after flipping.

I'm growing a couple now that easily stretched 300%; so the rule is only general in nature.

If 50 to 60 inches tall is too tall for your area look up LST, which stands for Low Stress Training.

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also look into topping

They have already been topped, I was going to wait till the 6 smaller ones that are around 15 inches now, get to 17 inches then flower, I have 8 foot celling.

steve kelley said:

They have already been topped, I was going to wait till the 6 smaller ones that are around 15 inches now, get to 17 inches then flower, I have 8 foot celling.

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Well it sounds like you should be fine then.
Good luck Bro.

$waGgEr said:

be aware a plant can double to tripple in size during flowering. plants should stay 28-30 in from an air cooled 600w hps....the bigger the plant the more it yields... it kinda depend on the space ur working with...if u have an 8 foot roof id say flower now

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28 to 30 inches?? Try 12 to 18. FAIL.

from my experience my plants grown under a 400w hps grow 80%-140% after switching to 12/12. But thats just my set up. basically double in size give or take 6"

I keep my 600w about 12-14" away from canopy but I also don't have any heat issues it stays at 74-75 at canopy.

steve kelley said:

How tall should I let my plant get before I flower them, to get a good yield? 3 of them (female seeds grapefruit) are 23 inches and 6 of them are 16 inches.

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for the best result
you need to get the whole canopy the same level a week before flowering
topping more if the strain takes well to topping
lst of lifting some of the pots up
most of the buds will grow on the top 12" of plant closest to the light
so if one plant is 6" higher than the rest, you will lose a lot of your yield

JASON79 said:

for the best result
you need to get the whole canopy the same level a week before flowering
topping more if the strain takes well to topping
lst of lifting some of the pots up
most of the buds will grow on the top 12" of plant closest to the light
so if one plant is 6" higher than the rest, you will lose a lot of your yield

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Aren't you concerned with the major blow the floral hormones in the plant take once there topped? it can take up to a month before they are back to full power again. If they don't have time to get healthy again you'll experience diminished yields.

its not the height that maters
its how wide the plant is and amount of nodes on it near the top of the plant that counts
if your growing in soil/soil less mix, how much and how big the root mass,

steve kelley said:

They have already been topped, I was going to wait till the 6 smaller ones that are around 15 inches now, get to 17 inches then flower, I have 8 foot celling.

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I didn't read how you were growing. You must also take into consideration what the containers you are growing in are stressed for. My current grow in NFT tubes. I needed to flip at 1 foot or under. I didn't. Take a look at my journal and you'll see where my largest plant fell into the tube. I'm going to lose all internal buds.

SirLancelot said:

Aren't you concerned with the major blow the floral hormones in the plant take once there topped? it can take up to a month before they are back to full power again. If they don't have time to get healthy again you'll experience diminished yields.

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(that why i said if the plant takes well to topping)
and that's why i said 1 week before turning to flower
and then it takes 2 weeks to start flowering, so if this slow the stretching you get in the first 2 week of flower it can only be a good thing.
if he has a uneven canopy, this will reduce yield

They are in soil and 4 an a half gallon pots

that pot will make a huge plant! Smaller pot, smaller plant.

steve kelley said:

They are in soil and 4 an a half gallon pots

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this is a good pot size if you can give the plants extra veg time i top and lst the plants
try to keep them short and get a large root mass there and you will be very happy with the yield
1 of my plants is 3ft x 2ft 30 inches high and min 30 bud sites at same height, 8 gallon container full root mass could of used a bigger pot
i will get 6-10 oz off this one
root mass in soil reflects your yield 1 gallon to 1 oz
in those pots you could pull 3-4oz each if grown right and get the root mass in
if you can keep the lights round 18-20" from plants, the buds mite not be as dense
but you will have larger foot print and larger yield
it would be good to find out more about your strain as some need to be closer to the light
but if yours is like mine critical mass i can have it 24" from plants large footprint dense buds and very large yield

I am keeping my 600hps about 13 inches above the plants and my 400hps about 10 inches from the tops,I have thought about flowering the taller plants under the 600HPS and the smaller ones under the 400hps, I will just raise 2 of the plants, so I will be flowering 5 under the 600 and 4 under the 400, sound good?

sounds good
if your using nutes, use grow for first 2 weeks
this will keep the leafs green later in flower