On 29/05/17 10:02, Michael Bell wrote:
I have been growing seedlings of Alnus glutinosa under light and heat.
All have grown well for the first 4 months.

In *Some* of them (and preponderantly from a particular strain) the
leaves have blackened died dropped off, the others have continued OK. Why?

Some notes:-
The lighting is Powerplant
The temperature is 43 C
The watering is Miraclerow made up manfacturers' directions.
I have been pretty regular about watering.

Where have I gone wrong?

Who knows? Guesses...

1.The strain doesn't like the Powerplant light.

2. You are cooking that strain. Why are you using 43 C for a hardy tree?
Even in its extreme habitat (North Africa) it would be unlikely to be
exposed to that sort of temperature continuously (and see point 4).

3. Why are you using Miraclegrow? Are you not using ordinary or seed
compost? Why do you assume the compost is exhausted after 4 months?
Maybe the Miraclegrow is too strong for some Alnus strains.

4. What does "pretty regular about watering" mean? If you miss one
watering when the temp is 43 C I doubt the plants would like it. Alnus
glutinosa appears to prefer growing in damp conditions, so if it dries
out that would not help.

If it was me, once the first true leaves have appeared, I would put the
seedlings outside and let them get on nwith growing normally. Forcing
any plant to grow will, in the end. weaken it. Just consider those
prepared bulbs which are forced. They usually aren't good for anything
for the next few years until they recover.

--

Jeff