I'm not sure of the exact growth period of this plant. It may be in late Summer or Autumn. If you're at all curious and don't know the exact name of the plant it seems to be Euphorbia leucodendron, the term "Pencil Cactus" while it can refer to this plant, is more commonly associated with Euphorbia tirucalli. The warnings about toxicity are the same for all Euphorbia though, so still be careful. :)

If it helps at all I just found this on a website when looking for dormancy and growth periods. "

Responds well to warmth, with its active growth period in the late spring and summer months."

Leucodendron! Neat. I don't know why pics show up squatty sometimes but if you click on pic it elongates and you can see how tall it is.

i can't remember when it grew last summer but I loved the little leaves and I read that's how it gets the little black dots on the stems

The pictures are only squatty on mobile devices so now worries. Yes, the polka-dots are nodes left behind by leaves. The "flowers" are yellow if it happens to bloom. I say flowers loosely because they are technically referred to as a cyathium or multiple cyathia as a plural, and are false flowers. Hope that's not too confusing.

And it actually does grow even without the leaves, you know, as long as growth conditions are there. Those leaves are indicative of the first flush of growth, IIRC.

Oh gosh, I need to start measuring with a yardstick! Thanks for that info. But I miss the little leaves.

I own a Euphorbia tirucalli 'Firesticks,' which also has cute little leaves on it as well. When they shed those leaves, they won't regrow them back at those leaf nodes. It will only grow new leaves on new growth.