Yellow leaves - water issues?

Hi all

I'd really appreciate your opinions on this. I have 5 plants, almost 3 weeks old. I live in Spain with long hours of good sunlight so this is my regime:

During the day the plants sit next to open balcony doors. They get good light all day including probably about 5 or 6 hours of direct sunlight. In the evening when the sun goes down I move them under lights - 5 x 25w cfl's total lumens 6500 for 5 hours, then lights out. So they r on roughly 18/6 (maybe some days they get a little more than 18 hours of light).

I'm using a good soil bought from a grow shop, no ferts yet (too young), and ONLY distilled water so I don't think it's a ph prob.

I'm building a grow room where they will be flowered under bigger / stronger lights.

They were doing fine but in the last few days the 2 lower fan leaves are starting to lighten in colour, becoming a little yellow. (the cotys are also yellow and droooping, but I presume this is normal).

Is this a watering issue? I can't believe that it is OVER watering because I'm very careful but could UNDER watering cause the yellowing? The leaves look strong and r NOT drooping.

When I water I use a spray bottle and spray on to the top of the soil until it is good and wet but not saturated, and I do this sparingly - not every day, perhaps every couple days. I also mist the plants several times a day while they are in the sun - keeps the humidity up.

Maybe it's a heat issue. It gets pretty warm in the sun - the plants pots are pretty warm, as is the top of the soil.

I would add some nutes now1/4 strength .Often yellowing is a N ( nitrogen)deficiency sign.the cotys yellowing is normal.

Yeah, maybe u r right gardenandcats. Odd thing is - only 2 lowest leaves r going yellow.

I'm interested to know how people water their young plants. Do u for instance flood the pot until water comes out the bottom then wait few days until soil is completely dry b4 watering again (like with more mature plants)? Or do you perhaps spray the surface only? I'd like to know...

Anyone else have an opinion which might help me? Nitrogen defeciency maybe?

It's not unusual to see some of the very lowest leaves drop. If it is only a couple lowers, no sweat. If the problem is spreading up the plant, look for trouble with overwatering.

Watering is hard to give useful guidelines on because there's so much variability in the drainage of soil mixes. You're looking for damp, not wet. When the soil is dry from the surface down to about 50mm or so, it's probably time to water.

Go with the flood method. Flood them until water drains out the bottom, then let them dry out completely. Lift your pots when they are BONE dry. That weight is the weight you need to water at.

This will allow your roots to get oxygen and avoid rotting them out. Don't continually water and keep them damp.

Al B. Fuct said:

It's not unusual to see some of the very lowest leaves drop. If it is only a couple lowers, no sweat. If the problem is spreading up the plant, look for trouble with overwatering.

Watering is hard to give useful guidelines on because there's so much variability in the drainage of soil mixes. You're looking for damp, not wet. When the soil is dry from the surface down to about 50mm or so, it's probably time to water.

Click to expand...

Thanks 4 the help Al. Boy, I thought everything was going too well. No probs at al up to now but those yellow leaves have started to appear and made me worried. If it is normal as u say then I'm relieved. It's a real bummer that watering is apparently such a fine art - I mean I been so careful not to overwater. And the plants look happy - NO DROOPING LEAVES at all, just the yellowing.

laserbrn said:

Go with the flood method. Flood them until water drains out the bottom, then let them dry out completely. Lift your pots when they are BONE dry. That weight is the weight you need to water at.

This will allow your roots to get oxygen and avoid rotting them out. Don't continually water and keep them damp.

Click to expand...

Thanks laserbrn. I think yr right with this advice and im gonna follow it.

yep, gauging by weight is a very good way to go. When you pot up, weigh the dry soil and pot. Water the soil, let it drain and weigh it again. Subtract the dry weight from the wet weight. When there's about 1/4-1/3 of the water capacity remaining, it's time to water again.