Some species are just hard to germinate; but how have the recalcitrant seeds been packed when you got them?
Before I was able to find live Mangosteen locally i purchased seeds on 3 different occasions from 3 different Asian sources. these seeds were all well packed, they arrived in moist peat, in zip locked bags and taped. non arrived crushed, some even sprouted on route, but not one grew. In this case I suspect it was the delay, the fastest order took around 18 days. since mangosteen can lose 75% of its viability in just 1 week, its no surprise. in contrast, the Garcinia aristata seeds I bought from a US source, gave me like 100% germination.
Are there many mangosteen trees that are producing in DR? Has your trees begun fruiting yet?
There are fruiting mangosteen here now, I have not seen them personally, but the seedlings I have are from these fruiting trees. there are only a few scattered around in private collections and in research centers. a person I know that is a Biologist in the country was able to get his mangosteen to fruit in just 5 years, using organic bio stimulants. my plants are still too small, about 2-3 years old with no branching yet.
First I have to mention that the mail in Mexico is not the greatest and is getting worse by the day , before I used to get seeds from all over the world in less than a month . Now only registered mail arrives , I guess the rest gets stolen ....
I never use regular postal service in the DR, I would probably not get one item.
I use a mailing service called "Business Mail" http://www.bmcargo.com/
Envelopes and letters are dirt cheap to mail in, and anything under 200 dollars pays no import tax. a letter may only cost me 0.60 cents dollars, to bring over. and even more important I have a US mailing address, and someone is there to receive packages.
But they will ship containers full also.
In Mexico there must be a similar type service available. everything from seeds, magazine subscriptions, parts, clothes etc. heck they even have a PC where you can order something on Ebay and pay them in pesos , and they pay Ebay. for those people that don't have a PC or Bank account in dollars.
Coincidentally there is a great supplier of these biostimulants in Mexico,http://www.agroquimicos-organicosplm.com/bioestimulante-33-2#inicio
I have not found similar products in the States yet, closest thing is what you see in Hydroponic shops. anyway that is for another thread hehe