Hi folks,
Complete beginner here, getting frustrated with trying to grow something that should grow like a weed!
My seeds (Royal Queen Seeds automatics) all germinate well (damp tissue method), and when their taproots are 1-2 cm long I plant them out in small pots, approx 0.5-1 cm deep. Compost is mgc24 “bio-hanf” peat-free brand. They grow, possibly a bit stringy, but maintain a nice green colour, on the windowsill. When they have another couple of pairs of leaves, after their cotyledons, I move them outside, to a SW facing patio with a wall behind them. It’s been warm, but rarely >30 C, and I’d say it’s been sunny enough - the rest of the garden is fine….
Then the plants stall - they get a few more leaves, never show any interest in e.g. the stalk branching, and turn a uniform paler green. They do not grow taller than approx. 10 cm, with my oldest plant from late May having started to grow a single tiny bud (is bonsai cannabis valuable :-) ).
The water here (Berlin) is quite hard, but still tests as having a pH of ~7. I’ve also tried watering with rain water and acidified (citric acid - it’s what’s in the Biobizz pH down) water.
I’ve tried Root Juice, Fish Mix and Alg-a-mic fertilisers from Biobizz, nothing seems to make any difference, and with such small plants it’s difficult to not overwater. I’d also expect the compost itself to still be providing enough nutrition for such young plants?
All help/suggestions gratefully received - thanks! Sorry for lack of a picture - for some reason it’s not letting me upload anything.
That is severe nitrogen (N) deficiency.
Three ways this happens:
Not enough N added in fertilizer/compost etc.
Organic matter with high Carbon:Nitrogen ratio locking up the N as it decomposes. In order for bacteria/fungi to break down plant material they need a C:N ratio of 30:1. Wood chips are 250-500:1.
Over-watering. Bacteria convert all types of nitrogen in aerobic conditions to NO2- and then NO3-. Both NO2- and NO3- are highly water soluable and leach out of the pot quickly. In severely waterlogged soils anaerobic conditions occur. This triggers bacteria to convert NO3- to N2 gas and it returns to the atmosphere.
Thank you also for the very detailed reply - from those options I think 1) and 2) are unlikely in my case - it’s a pre-fertilised compost designed for cannabis and should still have enough nutrients (plus during various stages of panicking I added N-Rich fertiliser (Fish mix) and no change occurred). This leaves 3, which has been the suggestion of others as well - although from your explanation I’ll be careful about reusing compost and will use new compost and add further fertiliser if required.
Multiple problems, mainly your roots. Probably not enough drainage and over-watering. Your roots are not able to breath and are under-developed. Now they can't use all the nutritions the plant needs.
Get some good substrate, maybe even invest in bio bizz. At least perlite for your substrate. And re-pot asap. Its not too late, she will be back if you give her the chance.
Nochmals vielen Dank! Thank you again - I’ve got compost left and some extra perlite so I’ll mix some more in and repot now.
If you have a bigger pot, use it! Cannabis needs a lot of space for the roots. They are "Tiefenwurzeler", not sure how to translate that one ;)
Deep rooters! I’ve just done some repotting before reading your reply, actually downsized slightly and added a lot of drainage as the roots were basically nonexistent and I’m trying to force myself to not overwater now. When the colour returns and the repotting stress has passed I’ll follow your advice and go directly to the “final” pot size.
I've always read that autos like to be in their final pot size from the beginning.
Thanks - more compost has now been ordered :-)
Those leaves look too light green, the plant is stressed. How often do you water the plant and how much do you give it? What is your metric for 'enough'? Do you let water sit in that tray? I would just start by watering it 1/3 as much as you currently do and see how it goes, the leaves will wilt if you are stressing it due to lack of water but in my experience cannabis can handle serious drought stress, they're champs.
Thank you again :-) I have been watering when the pot is light, and the top cm or so is dry, not letting it sit in water but watering enough that the water runs through. I’ve spare compost and perlite, so I’ll try quickly repotting, in case the soil’s now too compressed/waterlogged, then follow your suggestion re the watering frequency and try and forget about the plant a little!
Healthy plants need to be ignored just the right amount in order to thrive. Over watering is harder to recover from than under watering, for what that's worth. The leaves still look good, albeit a little light on nitrogen, so a full recovery is totally possible. My current grow experienced complete root loss at about the same age due to an equipment oversight, and you would never be able to tell with how lush and green it is now.
You got this!
Learning to ignore my plants just enough was the turning point in my weed growing career. Excellent advice.
Great, thank you! Just have to hope I can rescue them before the “auto” part kicks in - it would be a shame to have to start again.