"Sand" covers a lot of ground. As the particle size of the sand becomes larger than 1/10", perched water tables disappear; so sand larger than 1/10" and uniform in size would be a very good medium for rooting a wide variety of plants, including plumeria. As particle size becomes smaller than 1/10" a perched water table will be present and will become taller as the particle size decreases. It's important to be sure your cuttings aren't stuck so deep that the proximal end is below the ht of the perched water table, IOW, so the bottom of the cutting isn't immersed in the layer of perched water held in the soil.

Keep in mind that if you DO use sand that is finer than 1/10" and the plant roots, you'll still be faced with the limitations imposed by the perched water table as the roots try to colonize the soil occupied by perched water.

Perched water tables increase the intervals between watering, but they come at a price. Varying fractions of the roots that grow into the lower parts of the pot are killed within a very short time from a lack of O2 after watering soils that hold perched water, time that's measured in hours, not days. The plant then has to borrow energy from it energy supply held in reserve or from current photosynthate production to 'pay' for the lost roots as they regenerate. This lost potential would have been used by the plant to maintain metabolism at a heightened level, fuel growth, or increase it's reproductive capability, which translates into more blooms.

Al

I used to root in sand successfully all the time, beach sand. No idea of particle size. Seemed like the perfect rooting temp for them. My 2 cents

Pondplant,
You can dive into the science of a container later but your plant has to root and survive first. It will be very difficult to root if you pull it out to inspect. Leaving it alone is the best advice you can receive at this point. Especially since you have some confidence in using sand at this point.

If its working for you then keep it up but stay on the dry side of things until there are leaves. The whole purpose at this point to get the plant to root and then you would need to transfer it to a more permanent planting media anyways.

Jim Little wrote to using beach sand as a possible rooting medium in his book. He proposed sea salt may have some antiseptic qualities and did not appear impact the cutting negatively. I would surmise he was referring to North Shore of Oahu sand which is relatively course when compared to the sugar sand on the mainland. Hope this helps and good luck with it.

I root in sand in a small bag, easy for transplanting.

Will, plumerias stakes root in the dark? (in s warmer. Windowless bodega)?

Short answer....yes

Long answer...yes but needs warmth from a heat mat or other means and expect any growth to be colorless and weak. IOW I would do it for a few weeks if no other way but not for much longer.