Cacti growing experts please have a look

[HeartCore]

Hey,

Two of my San Pedro seedlings look like this. What do you think is the most likely cause?

- humidity too low
- humidity too high
- over feeded
- under feeded
- etc..

Thanks

 

[Ultima]

are they still growing? they look sunburnt

 

[Mr.Smith]

.

 

[user_1919]

Make sure they get diffused light. They need light, just not the same intensity as a full grow cacti would get. Add some waxed paper in front of the window or something. Goran will be able to help you much more

peace & love

 

[Ultima]

i had some peyote that looked like that, im pretty sure its either too much light(almost possitive) or too much water.

 

[HeartCore]

Thanks so far for the replies. It's only two cacti that have this problem. I'm growing around 50-60 now with some more on the way. All other's are looking fine, like little spiked green thumbs sticking out.

I've managed to make a few better pictures. Following advice here, I've put the 2 fts which provide light a little higher and I put the two cacti back in a terrarium with only a fluorescent bulb and high humidity. If the light was causing the problem, I wonder why some of the much younger ones which where under similar conditions didn't show any signs of trouble.

Something I forgot to mention, I've added 1/10 of cacti fertilizer to all cacti older than three months. Could that be the problem? Overwatering does not seem a problem, the soil was dry and I water twice per week.

Anyway, they seem a little better than before but maybe someone else has an idea seeing these new pics.

 

[Ultima]

i wouldnt feed them cacti fertalizer untill they are at least a year old.. i had some trouble with that as well.. i managed to kill some of my peruvians because of that. (i only put 3 drops of cacti fertalizer into 1liter of water, and it killed like 10 of them) all naturell is the way to start em

 

[tryptonaut]

Depending on the soil mix you are using, there is already a lot of fertilizer in there - maybe almost too much for the little seedlings.
You really don't need to fertilize them until they have a root system that is at least covering 1/3 of the soil inside the pot.

 

[Goran.Hrsak]

Overburned with water and rich soil! Hell with cacti fertilizer!

 

[tryptonaut]

... the soil mix usually sold as "cactus soil" (and from the pictures I guess this is what was used?) is mostly over-fertilized for most cacti, even adult ones, because they put in too much peat and humus (which are cheap mass products).
They just mix that with some sand and maybe a little perlite and label it "cactus soil", but it's not reallly cactus soil.*
If you're growing San Pedro or other Trichocereus/Echinopsis you are lucky because these guys actually need a little more humus and fertilizer than most cacti - but the tiny little seedlings (just like seedlings from any other plant) should best be grown in special sowing soil with near to no fertilizer.

*I bought some special cactus soil recently from a big specialized cactus dealer and it really was totally different from the stuff you can buy everywhere else. They put in stuff like lava, different mineral stones, even some special sort of clay and almost no humus. For my grown Pedros I mixed it with a bit of normal potting soil because they can use more of that than other cacti.

 

[skoeip]

normal cacts soil contains small wood chips and when those decompose they rip nitrogen out of the soil and thats a big no no for cacti.