I have noticed some of my astrophytum seedlings are starting to turn dark brown/orangeish towards the bottom. I've read that some seedlings will turn brown-red under bright light but that it on the top of the seedling. I have mine under a 100w grow light about 18 inches from the seedlings and I have some melocactus seedlings that are growing well in the same conditions as the astrophytums.
100w grow light about 18 inches from the seedlings
Looks too far from seedlings and these look elongated for me. Don't be afraid of reddish pigmentation - this means the light is sufficient. Brings lamps or seedlings closer, like 10 cm away. this will make them healthier and shape more typical for that plant. Only brown colour at the base can be harmful as from fungus infection. So it's a good idea to keep temperature high (>20 - 30 C) if the mix is not sterile sealed or let the surface to dry out between waterings.
If your cacti mess in your job just forget about the job.
°C = (°F - 32)/1.8
Ah, I thought they were fine for light but I’ll move my grow light closer. I have them on a heat mat that keeps them warm and haven’t watered them since they were sown, as there is a cover over them most of the time to keep the moisture in and humidity up. I’ll keep an eye on the ones with brown bases for fungal infections as well.
