Does anyone know anything about browning in bridgesii cacti, and whether I should be worried about this? I acquired half a dozen cactus seedlings in September of last year, and I water them every week or so. They're on a window sill which receives about 4 hours of direct sunlight a day, and indirect light during the rest of the day. Where I am it's winter at the moment, and it gets to be around 45 degrees Fahrenheit during the middle of the night.

I've attached a couple pictures of the cacti, sorry about the low webcam quality though, any part which looks brown in the picture is about twice as brown on the cacti.

You are probably over watering those babies. In the winter they go dormant, especially if they're only getting around four hours of direct light, and with temps as low as 45 degrees. They need zero water when dormant, and are prone to rot if they are watered. They may not be a desert cactus, but they take to dry conditions nonetheless.

If they have rotten, hopefully they'll fight it off. If you could put them in a warmer place with more hours of light they might grow in time to out grow any rot. They could really use this anyway, since they are pretty small still. In nature they would germinate in the spring, grow all summer and hopefully be big enough to hibernate the winter.

Twice a month to once a week watering is a good rule of thumb in the middle of summer, not winter.

Alright, cheers . I moved those two to another location with a bit more sunlight, and will wait until spring to start watering these guys again.

I killed an old Trichocereus friend by watering it once a week during the winter. When I dug it up to check the roots, they were totally rotten! Don't water it again until it's very dry. Even when mine are actively growing, I tend to water them only every 2-3 weeks. More sunlight never hurts either.