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I had a cactus at work since the end of March. It is my first cactus and I don't really know if I was watering it correctly or if I missed something else, but now it's turned yellow and became softer. I googled around, but I can't tell if I'm identifying the problem correctly and if this is a case of overwatering, some sites say that all that's left is to dispose of the cactus, other say to just leave it for some days.

The question is, is there anything I can do to help it? And how can I prevent this from happening.

Some info: the cactus is on the table, about 2-2.5 meters from a window which more often than not has its blinds shut. Also, the last couple of weeks have been quite hot, so the window was often opened. There may have been draft from time to time, but not for long periods of time. I've been watering it two times a month, every other Friday, until I saw a drop or two of water come out of the drainage hole in the bottom of the pot. I don't know how much water it was precisely, but if I had to guess, I'd say about 100 ml each time. Nothing else has been done since I bought it. At the moment the ground it completely dry and I was going to water it again this Friday.

edit: Also, I sprayed it with water two or three times during the time it was here.

The cactus in question

J. Musser
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Anton Zujev
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1 Answers1

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I don't think you are overwatering at twice a month. What I DO see are salt deposits on top of your soil. This is from softened tap water. Not good. Repot with soil made for cactus. Check the roots. If any are mush, cut them off and wash them. In fact, if the roots supporting the yellowed barrel are mush, I'd probably get rid of that part of the plant. Make sure that just the roots are back in the soil and no soil is touching the cactus. Water lightly and wait to fertilize until the plant can acclimate to new conditions. You might lose the barrel in the middle, but the others will do fine.

When the window opens, is the cactus getting direct sunlight? It could have even gotten sunburn without the protection of the glass...spraying with water is a good way to water a cactus or succulent. Washes off dust, possible insects and their root system is so shallow that wet soil below the roots could cause problems...or in this case, if the pot the cactus pot is sitting in doesn't have a drain hole, sitting water will cause root rot. Get a new, shallow, clay pot with drain holes and use a tray to catch water (dump water out of tray). Get distilled water and stop using tap water.

The little green barrels that still look healthy can be broken off the parent plant and placed, raw end down in the new soil (make sure you get sterilized potting soil just for cactus). Use your sprayer to keep the top of the soil moist, not wet.

stormy
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  • Thanks for your answer. Are cacti sensitive to tap water? We have another plant here at work that we also water with tap water and it looks pretty healthy. The water stays in a watering can for a week or more before we use it. I'll try repotting the healthy parts and use distilled water from now on. – Anton Zujev Jun 04 '14 at 05:45
  • Hi Anton! Most plants don't tolerate salinity. The salt build-up takes time, but once it accumulates it can kill your plants. I am more worried about water standing between the two pots for your cactus. Go ahead and use tap water but try to get a couple cheap bottles of water from the store. You'll be able to see the build-up, especially if you have clay pots. They show on the outside as well. I hope this helps...the chlorine evaporates, but not the salts or fluorine. You don't drink tap water do you? Grin!! Seriously!! – stormy Jun 04 '14 at 06:03
  • Also, is it safe to use distilled water? I mean, it is completely cleaned of everything. Or should I mix it with minerals or something? – Anton Zujev Jun 04 '14 at 06:04
  • I actually do drink tap water. :) – Anton Zujev Jun 04 '14 at 06:05
  • Stop drinking it...look up fluoride. No you don't have to use distilled water; bottled water or well water that isn't conditioned would be even better. I was trying to be more brief...sigh. If you have friends with well water, get some from them to drink yourself. I just learned about the fluoride this past few months. Haven't even thought about the effect fluoride has on plants. Let me know how things go... – stormy Jun 04 '14 at 06:12
  • Just for the info. Looked up the fluoride. I'm from the Czech Republic. We try to control the quality of tap water here. Here's the latest study I could find: http://www.szu.cz/uploads/documents/chzp/voda/pdf/monit/voda_12.pdf. It's from 2012, but was allegedly updated in 2014. It has a whole section on fluoride (sadly, in Czech, although everything else is translated) and it states that the amount of fluoride in tap water doesn't exceed that in other water sources. For my town it's 0,125 mg/l on average, with the state imposed limit being 1,40 mg/l. I don't know if that's good or bad though. – Anton Zujev Jun 04 '14 at 06:59