Question
Our cactus seems healthy, but recently its many leaves turned yellow and are all
falling off. Is this a natural response to the change in seasons, or is it lacking
some nutrient, being over- or under-watered? Please advise

Answer
Dear Lisa,

In general, Euphorbias are deciduous, which means they will drop their leaves. This time of year is common for that to happen, mostly in response to the shortening of the days. Continue to water only when the soil is dry, although when it is actively growing and in leaf, you can increase the watering slightly. Hope this helps.

Sincerely,

Greg