Melissa – USA:
I have two Euphorbia tirucallii (pencil cactus). One is getting pretty large and is basically growing sideways towards the sun instead of growing up. It is also starting to turn white. In the fall, it usually turns a reddish color. I repotted it into a larger pot this past June, so I feel like the pot is the correct size. The other factor is I live in Phoenix, so it is very hot in the summer and doesn’t get below freezing in the winter. The plant stays outside year round. My smaller pencil cactus is doing great. Also, I moved this past June and where I lived before, about 10 mins from where I live now, the larger pencil cactus received the direct afternoon sun and did great for the three years I lived there. Where I live now, the patio is receives much more shade, but still gets light. In the summer months, I water them every other day which is what I was told to do when I purchased them and in the winter, I water them once a week. Why is one of them turning white and am I watering them to much?

Answer – TAD:
I’m not sure what the white is – if it can be rubbed off it’s a fungus. If it cannot be rubbed off I suspect over time the sun has bleached it. Problems with succulents don’t show up instantly when growing conditions are wrong. Sometimes it takes a long time to see a plant react to a bad situation.

You should not water the plant every other day or every week but only when the soil has almost dried out and it will not dry out within a couple of days or even a week if it’s in the house and in a big pot. Over-watering can cause discoloration too.

The pot size should be such that it comfortably fits the plant. If the pot is too big for the size of the plant it will just hold more soil which will hold more water for a longer period of time which can often end in root rot.

Melissa – USA:
Thank you for responding to my email.

The white on the plant can’t be rubbed off. What is supposed to be green is now white. Forgot to mention I planted it in cactus soil. I’ll stop watering it so much.

Thanks again for responding. Your website is great, glad I found it.

Answer – TAD:
My pleasure.

Euphorbias are not in the cactus family. They are one of the ‘other’ succulents. Cactus soil, especially some of the very sandy pre-mixed potting mixes for cacti, are too lean for euphorbias. They require a more nutritious soil mix with more soil and just enough sand or grit to make the mix well draining.