Cornell Cooperative Extension
of Westchester County

Gardenia Question:
Q. Why does my gardenia fail to bloom even though it appears to be healthy?

A. Lack of bloom concerning gardenias can have a great deal to do with giving the plant proper night temperatures during the winter. Place your gardenia in a spot where it will receive ample bright light such as sunlight filtered through a sheer curtain or blind (an East window can also be suitable) but where night time temperatures fall to about 62 degrees. This night time temperature drop should assure flower bud formation. Always avoid placing the plant near radiators. When the weather warms in mid to late May, place your plant out of doors in partial shade. The sunlight that filters through a tree without dense foliage seems ideal. Bringing the plant back into the house in late summer before the heating system is turned on usually prevents a great amount of leaf loss from "relocation shock". Of course, cultural practices consistent with the healthy growth of gardenias still apply. Water the plant when the soil surface is just getting dry to the touch and remove any water that remains in the drainage saucer longer than 1/2 hour by using a turkey baster bought specifically for this purpose. Always remove the drainage saucer when the plant is summering out of doors. When transplanting, use a soil that is rich in organic matter, yet drains freely and does not become soggy. A standard flowering house plant fertilizer that is not too strong is best applied from spring to fall. If the plant shows signs of chlorosis, a house plant mix containing increased amounts of peat moss may be advisable the next time you transplant. Apply a standard acid-type fertilizer at the reduced house plant rate per label directions until the soil can be amended. A note about sunlight requirements: Despite many repeated and well intentioned attempts, the establishment of standardized yet understandable definitions of different light levels for house plants still seems elusive and sometimes both unintelligible and unattainable. Regarding gardenias, I have seen them grown successfully in a full sun, south facing bow window from late October to late February with no sign of foliage injury. Yet, many sources warn us to keep them (always) out of direct sunlight in winter often using the proverbial curtain or blind. Clearly, there are indoor "light microclimates" to match every window, window treatment and windowsill, so start by filtering bright light as best you can or by keeping the plant to the side of a sunny window in a bright room. If it's clear that your plant needs more light in winter, try slightly more exposure. Foliage injury from too much sunlight will occur fairly rapidly so be observant and adjust light levels accordingly. Remember also, that as spring approaches, the sun becomes increasingly more intense so be prepared to move your gardenia "back, aside or behind" until it's time for its summer vacation out-of doors.

Gerald G. Giordano
Senior Horticulture Consultant
Extension Community Educator
CCE Westchester Hort Team

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For more information please e-mail westchester@cornell.edu

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