From Wikipedia: "They require a warm subtropical to tropical climate that is cool but also frost-free or with only very slight winter frosts not below âÂÂ4 ðC, and with high summer heat, rainfall, and humidity. " They need high humidity ... really high humidity. And acid soil Also, they may need cross-pollinating by a different variety ... "Isolated or single lychee trees will usually set acceptable amounts of fruit. However, recent research has demonstrated that under some conditions, cross-pollination among different cultivars may increase fruit set. Therefore, in some cases there may be an advantage to planting more than one variety. " Here is a link that might be useful: California Rare Fruit Growers

You should post this in the Tropical Fruits Forum. Lychee is one of the biggest topics there......

so you moved it from inside to full sun? That sounds like sunburn. You need to move plants gradually into the sun. I would trim off the dead leaves and move it to a shadier location, edging it out into the sun over the course of a week or so.

wow... need more info... any changes in the soil or weather ? (recent flooding / drought ?) have you checked under the leaves for fungus or insect damage ? How fast did this happen... was it healthy looking a few months ago or ? have you fertilized recently ? the yellowing looks like mineral deficiency, but if it happened all of a sudden, maybe not... the 1 thing i know about Lychee, is they have a very close relationship with soil fungi... if the right fungi is in the soil, they do great. if not, they normally just dont grow and start to slowly die. If it is the soil, you can add fish fertilizer, mycorrhizal fungi, good compost and worm castings, and it should perk up. you have another plant growing near it...? what is it ? the roots may interfere...