Need a little help from the experts....

Hi there, i'm new growing my little plants and have recently discovered a problem. I have two plants which were happily growing on a window sill for 5 weeks until I moved them to a grow cupboard under a sodium bulb to give them 12/12. When they were young i used a 10/10/2 fertiliser but how now moved on to a lower nitrogen 12/25/25 fertiliser. They have been under there for 5 days now and one of them is showing signs of unhappiness on the leaves (upper ones especially) and although the other one seems to be happy the leaves are lighter than I feel they should be. After reading up on the forums I thought that it could be either heat stress or a lack of Molybdenum. The problem that I have is that the strange leaves (see picture) are on the smaller plant which is further away from the light and the taller one (closer to light) is not showing these signs. The fertiliser i use also contains trace amounts of Molybdenum (0.002&#37. I know there are geniune experts in this field who post on this board and would greatly appreciate it if you could give me some advice. Thanks in advance...

So what do we have here then?

Firstly how do you figure out that a fertiliser of 12-25-25 has a lower Nitrogen content than one of 10-10-2? It's the N figure you want to be looking at and that's the first one in N-P-K.

Secondly pumping a plant full of nutrients isn't going to help in anyway if the deficiency is being caused by any other factor other than a simple lacking of those nutrients in the soil substrate and that doesn't actually happen that often if a correct feeding schedule is adhered to.

So, this problem started when you put the plant under a HPS. The natural assumption to make would be that the two are linked and they probably are but perhaps not for the reasons you might think. I would suggest the problem has been caused by the higher light level of the HPS compared to the windowsill sun and this has caused an increased requirement from the plant in water and nutrients. For some reason the plant cannt access some of these nutrients in the soil substrate and this might be being caused by a number of things. An out of whack water ph would cause it, so would a build up of chemical fertiliser salts in the rootzone as well as a soil substrate with no nutrients left and a plant that's simply outgrown it's pot size.

The solution therefore is to decide which you prefer to do. You can repot into a fresh pot of soil and work out the correct feeding schedule or you can water flush the soil medium to rid all those excess salts and continue with a correct feeding schedule. Check your water ph to take that out of the equation.

great advice , and I want to add that I learned the hard way that you have to check and balance your ph after you introduce the nutes into the water. I also highly reccomend journaling everything you do like a scientist. Especially if you smoke because sometimes we stoners can get forgetful.................lol\


but the journaling will help you to establish water patterns growth patterns/spurts etc., Good luck ~

Hi there and thanks to both of you for your advice. I do 100% stricly follow the feeding guildelines that are instructed on the packet, although I give them several extra waterings during the day to stop them drying out under the lamp heat. I'm thinking it is the PH which could be the problem as I have stubbornly put it off, hoping it would all be ok. If not I will try repotting in larger pots to make them happier. As for the lower nitrogen feed, I was just reading out what it said on the packet to give you a bit of depth into what i have stumbled my way across so far. Thanks again for your help!

You know, PHing is the one thing I've never done with my grow. I bought the soil testing kit and just never saw a reason to use it. Luck, I guess....

hearmenow said:

You know, PHing is the one thing I've never done with my grow. I bought the soil testing kit and just never saw a reason to use it. Luck, I guess....

Click to expand...

You shouldn't have to ph the water in soil grows - the soil buffers the ph to an extent stopping it going too high or too low. It's only when problems start that its helpful to take the ph out of the equation, but it's not essential and rarely ever is the actual cause of the problem as I believe to be the case here.

If you want 100% control over the feeding of your plants controlling ph is vital, but for the majority of people growing in soil its not neccessary.

If it helps I have a similar prob. I'm growing indoors next to open balcony doors. The plantstherefore get good light all day including 5 hours of direct sun per day. (I live in Spain and wanted to utilise the good sun here, and then later flower under lights in a grow room that i'm building).

In addition to the sun I was putting them under lights after the sun went down for another 4 or 5 hours each day (5 x 25w cfl's). When they were about three weeks old problems started developing with yellowing of leaves. On the advice of the guy in my local grow shop I stopped giving them the extra artificial light. He said that my grow is basically an outdoor grow and the that sun should be enough, stop the extra lights and let the plants rest after the sun goes down.

Maybe yr plants r reacting somehow to going from sun to artificial? As I said, I plan to flower under lights so hope I don't get same prob.

Hmm, the problem is still there one the smaller one, I tried increasing the ventilation if it may be the heat but i'm simply not sure. Well they are just starting to flower and it doesn't seem to be causing any problems to the rest of the plant to i willj ust have to wait it out.

I think babygro is spot on, the increased levels of light and the increase in heat from it running is making the plants need more water and nutes, basically the light and the heat are allowing the plant to grow faster but the nutes are holding it back