Lithops and algae

[GreenHairsteak]

Hi, I’m growing some lithops seedlings. Over the last week I’ve noticed some green algae type stuff on the surface. Will this effect my young lithops and what should I do?
Thank you

[img]http://i.imgur.com/odeXW1s.jpg[\img]

[Diane]

It shouldn't be a problem - algae almost always forms on the compost surface of seedlings. It only becomes a problem when it grows large enough to swamp small seedlings, and yours should grow large enough not to be affected.

[MikeDom]

These are some of my lithops seedlings from the BCSS Seed Pool sown 4 months ago and you can see the algae on all of them hasn't inhibited development of the seedlings. The only thing you have to be careful of is touching it when the pot is dryish as it comes off in layers and you can pull the seedling out with it. Examples of the layers that come off are in the pot top right with the solitary Rubragold. It might be because I cover the seeds with a very fine layer of [dry] silver sand. I'm sure the algae doesn't help in getting air to the roots but I don't have a problem with damping off or root rot.

[rodsmith]

I would add to the above comments that lithops seedlings (unlike cactus seedlings) don't like to be constantly in wet soil. I have found that allowing the compost to dry out between waterings tends to kill off the algae and prevents the young seedlings from rotting.

[GreenHairsteak]

Thank you everyone, that has been very reassuring!
The lithops seedlings are a few weeks old now.. what would you advise regarding watering needs?
Thanks again.

[MikeDom]

Happy to help. It depends to a certain degree on the compost you use and the ambient temperatures. I use a 50:50 mix of Westland John Innes No. 3 (I don't get any sciara flies with this brand) and RHS Grit Sand. At the stage your seedlings are at, I wait until the top of the compost is starting to dry and is a bit crumbly before watering by spraying the compost around the plants with just water until it is wet. If you knock the plants out of their pot before watering you will see that the compost is damp for at least the bottom two thirds. The algae, being shiny, can give the impression that the compost is wet, hence the need to disturb the compost a bit. After 3 months I leave it an extra week before watering and soak the pot with a 50% strength feed of Chempak 4 High Potash feed (others use the Low Nitrogen one but I never have). As an example, In the heatwave we had I was watering once a fortnight, at the moment they are watered every 3 weeks or longer. Wait until spring before repotting.

[GreenHairsteak]

Thank you for the detailed response, that’s really helpful for a novice like me.

[David1971]

I agree with all comments of Mike, Rod and Diane. Lithops seedlings are much more drought-resistant than it could seem, so watering just enough to ensure growth while maintaining a good ventilation minimizes algae and other (much more important) problems.