Moving from one location to another, too much heat or dry air, or waterlogging or dryness at the roots may contribute to this trouble. This problem can be minimized by maintaining constant levels of high humidity and uniform moisture levels in the potting mix. It is also helpful to maintain temperatures around 70 F and to avoid high temperatures, especially at night. Chlorosis , iron deficiency. This is probably the most common and important problem on gardenia.
Leaves appear yellow or chlorotic and have green veins.
Growth may occasionally be retarded and highly symptomatic leaves may drop. In most cases, the condition is associated with the unavailability or deficiency of iron in the potting mix. Chlorosis can be avoided by using a fairly light, slightly acid potting mix. Insect Problems Fuller rose beetle, Asynonychus godmani . This weevil sometimes injures gardenia.