Yellow Fever

[Suet]

Ok, frist I'll give you guys a run down of my plants history and then tell you about my problem. We germinated the seeds under two 2 foot flouro tubes (one grow lux and one tri phospour) until they where about 7 cm tall. They where looking quite healthy, and we had fertilised them once with some miracle grow.

 

Then, for reasons that I'd rather not go into, we had to tranfer the plants into a small cupboard and we put them under 2x48 watt compact flouros.

Now the top sets of leaves have begun to turn yellow, it started from the middle of the leave and its looks kind of like a rash, its really wierd. I think it was either too much light or the lights are too hot, but I thought I'd better ask the professionals. The bottom leaves where also turning yellow, but it started from the tips and it looks like the leaves are dying. I now have put the plants back under the 2 foot tubes but they are not recovering very well. I have two computer fans circulating air in the cupboard and the plants where transplanted into bigger pots about a week ago, before they where put in the cupbord.

 

Any diagnoses/general suggestions would be very helpful, this is my first grow and Im really getting into it.

Thanks heaps.

[Ozzy420]

Hi there Suet and welcome to ozstoners it sounds like thay have fertilier burn, how old are thay the 2 48w cf should not burn them, so u mite have to give them a good drink of just plane water flood them so it washers out the nutes and if u are growing in soil set the ph to 5.0, a few of the other growers will be able to help u ouit a bit more.

[Tom]

How much water are you giving them? What sort of potting mix have you used? Have you checked the ph of the new soil? If you have used a good quality soil you shouldn't need fertiliser for another week or two yet.

[Suet]

We use some pretty cheap potting mix that we got from Woolies and they where watered about 2 times a week. They where reppotted about a week ago and some sheep poo was added to the soil then. We've fertilsed them 2 twice since they germinated, which was about 4 or 5 weeks ago.

 

Does fertiliser burn start at the tips of the leves ?

 

It started the day they where put under the 48 watt compacts flouros, and they hadn't been fertilsed for a while then, and now they are under the 2 tubes, the rate of growth of the yellowness has decreased. I have no idea what the pH is sorry. It gets quite hot in the cupboard, this is a stealth grow and I had to sacrfice ventilation for security, theres not much point in producing a bumper harvest if I get busted before I can harvest it, but I suppose what's the point of being secure if my plants die...

[Luke Skywalker]

Sounds like fert burn... If you have sheep manure in the soil already the plants shouldn't need supplimentary fertilisation for quite some time yet. How much poo to how much potting mix and in what sized pots?

 

Fertiliser burn starts at the tips of leaves and progresses up. As the nutrients are in overdose they are also out of balance. If you haven't been checking and maintaining ph then you are most likely also experiencing nutrient lockout. You can get a ph testing kit from bunnings or a similar garden center, you'll need a soil one. Range for soil is 6.3 - 7.0 or so.

 

Immediately cease all supplimentary fertilisation and water the system thoroughly... I mean flush the things right out, that will remove most of the soluble fertiliser chemicals left in the pots. After that you'll be leaving it without ferts for a while, and get that ph checked and adjusted if need be. Depending on how much poo you used when making the mix, and how open this mix is, you won't need to fertilise for quite a while.

 

While I'm at it, you cannot sacrifice ventilation full stop. There is no crop without venting. The air needs to be exchanged, and it needs to move around the room, otherwise your plants will not give out anything like a harvest of any decency. Heat is not the only issue here, it's also fresh air and co2 getting to the plants and humidity too. Get a small oscillating desk fan in there to gently blow over the plants too, this will encourage it to grow strong stems and will also keep moulds at bay.

 

Stick to the basics of growing indoors, light, water, air, temps, nutes, media. And love, of course. Get all those factors in the right ranges, then you're laughing, and the plants will just go and do what they do best. If you need help with the specifics, just ask. But you need to get an extraction fan in there asap mate, and you also need to flush them too.

 

Hope that helps.

[Suet]

Thanks for the advice.

 

I drilled a large hole in the back of the cupboard and I have two computer fans blowing air onto the plants and I'll begin to flush the soil.

[Luke Skywalker]

You need more than a hole in the side. Use one of those computer fans to pull air out of the grow, if noise is a concern they can be silenced somewhat by suspending them with rubber bands... The extraction fan will need to be at a high point in the grow, as it's there to pull out warm air. Next, you'll need an intake, you only need a passive one, at least as big as the outlet, better if it's bigger. If both fans are identical then you could use one as an intake as well, along with another passive intake, but honestly, you'd be better having two extractors.

 

Anyway, hope that helps, if you need some tips on how to set up your growroom check out the links in my sig, and have a look in the growfaq... there's heaps of info here to if you use the search function.

 

Keep us updated on the plants too...

[pipeman]

fans become a helluva lot quiter if you fit a short length of ducting maybe with a bend to trap light. Mounting on rubber bands will assist as well. or, if screwing to surface use rubber mounts or buffer with stick on rubber stops or foam or something. Also, wrapping rockwool or other insulation around the fan and the ducting for about a foot either side it makes it a HELLUVA light quieter. I've seen a big noisy motherfucker reduced to bearly audible standing right next to it with this method. Most hydro shops sell fans with flanges ready to fit ducting. They sell the ducting as well.

[Suet]

Thanks for the advice, they are looking alot better but I still have a couple of questions. Should I cut off the yellow leaves (they look pretty dead) or just leave them ? Also there are some tiny black flies living in the pots and the lowest leaves have got a couple of brown spots about 1mm across, should I be worried ?

 

One plant is about half the size of the other, Is there a way to get it to grow taller ? all the nodes and leaves are quite crowded.