I don't grow Longan but grow Lychee...they have similar growing conditions I believe? Longan being less fussy and might be more tolerant to frost than lychee.

You don't say what zone you live in? Are you planting this in the ground or in a Pot?

I believe lychee and longan both love water and don't tolerate the soil drying out completely....Keep the soil "moist" NOT sopping wet or the roots and leaves get damaged...

If you're planning on growing it in a pot...here's a link below from the Tropical Fruit Forum a while back...Good luck!

Here is a link that might be useful: Growing Longan in a Pot...(GW)

I'm in southern california and going to plant it in the ground