In Florida, all Garcinias take off like rockets with Sequestrene 138. iron: Specifically Sequestrene 138 is steroids to Garcinia seedlings. I had Garcinia seedlings idling for a few years until I started giving them that stuff. OMG, what a difference! Just sprinkle a little in the roots and water it in. Spray it at a rate of 30 gms per 100 litres of water with some dish soap and 100 gms of Urea. Do it once a week. Additionally break up the soil around the trees and add 200 gms of bloodmeal and work it in deeply. Monitor your progress watching the new leaves.
Put loads of mulch around the trees.
Chelated iron has really made a difference in my Achachairu plants. They respond to chelates even in my adverse climate. Limoncillo is another Garcinia that shows improvement after a generous regime of chelates. Ref: Sérgio Duarte, Algarve, Portugal.
Mangosteen – I purchased an electric blanket to hasten mangosteen germination and growth during our Innisfail winter and this is what I did: Fill deep plastic food containers with damp perlite and coconut coir. Sowed mangosteen seeds and a few small transplanted mangosteen seedlings. Wrapped the food containers/with lids in the electric blanket. Switched the heat setting to give approx 27-30 degrees C around the clock. The results in just a few days are pretty amazing. Within 4 days, Mangosteen seedlings (previously growing outside in the garage in forestry tubes for 3 months) with ¾” shoots and no sign of leaves, put on major growth spurt to reach 3” tall with small leaves. I estimate the increase in growth speed to be maybe a hundred fold. – Greg Woolley in Innisfail