Once a gardener gets a whiff of the beautiful, pure white blossoms it is hard to forget the experience. These beautiful plants, with their dark green, shiny leaves and intensely fragrant flowers are available in three different varieties. The popular "Mystery" gardenia, with its 4 to 5-inch flowers; the "Radicans", a small low-growing plant, 6 to 12 inches high and the "Veitchii", a compact form, 3 to 4 feet high, with 1- 11/2- inch-wide flowers that blooms almost year 'round.
GENERAL CARE
Gardenias are fussy plants. They like to be given ample water, ample feeding and ample warmth. The soil they are to be grown in must be acidic, otherwise the leaves turn brown and the buds drop. They need regular treatment with iron and doses of aluminum sulfate to keep the soil acid and keep iron chlorosis from turning the leaves a pale color. Feed them monthly during the growing season with an acid food, one prepared for camellias, azaleas and rhododendrons. Many successful gardeners use Miracle-Gro or Miracid as a foliar spray and as an aid in correcting iron deficiencies.
Gardenias prefer being planted in a place where they get full sun in the morning and shade in the afternoon. Plant them in the ground with the crown (the part where the stem arises from the ground) raised slightly above the existing soil. This will help prevent root rots. Gardenias do not like their roots disturbed by cultivation. Cover the area underneath gardenias with a thick layer of mulch. Once established in a place they like and given proper care, gardenias will bloom their hearts out, providing an abundance of fragrant flowers for you to enjoy.
SOME COMMON PROBLEMS AND SOLUTIONS
-- Salt "burn" on the leaves. Salts found in alkaline soils tend to concentrate in the edges and tips of the older leaves, killing the cells and turning the edges brown. Keep the soil acidic with applications of aluminum sulfate. Purchase a soil testing kit, one for testing the pH of the soil. One such kit is the Sudbury Garden Soil Tester. It costs about $4.00 and will give about ten tests. The instructions are easy to follow. To lower the pH of the soil the gardenias are growing in, add 1/4-1/2 cup of aluminum sulfate to the soil at the base and under the gardenia and water in well. This will lower the pH about 1 point. Wait two weeks. Test the soil. If the pH needs to be lowered even more, reapply aluminum sulfate. Test the soil once a month in the summertime, adding the aluminum sulfate as needed to keep the pH to 6.0.
-- Iron deficiencies. The leaves are pale in color with the veins still green. This is a symptom of iron, magnesium or zinc deficiencies in the soil. This condition is also known as chlorosis or iron chlorosis. Treat the soil to lower pH with aluminum sulfate. Use 1/4 to 1/2 cup of aluminum sulfate spread around under the gardenia and water it in. Spraying the leaves with Miracle-Gro or Miracid, in addition to acidifying the soil with aluminum sulfate, will give a quick, but temporary, fix for iron chlorosis.
-- Sooty mold. The leaves are covered with a blackish, sticky stuff that can be wiped off Sooty mold is a fungus that grows on the exudate of sap-sucking insects such as aphids, whiteflies, scale insects and mealybugs. The mold can inhibit the food-production in the leaves. It usually will wash off in the winter rains. Prevent sooty mold by controlling the insects causing the problem. These insects may be on the gardenia or on plants growing above them.
-- Insects attacking gardenias. Commonly found are aphids, scales, whiteflies, spider mites and mealybugs. Control them with Orthenex or malathion. Organic gardeners use insecticidal soaps, horticultural oil, pyrethrins, ryania, or sabadilla.
-- Buds dropping and leaves yellowing. These are attributed to abrupt climate changes, excess watering, or both. It usually occurs in the winter. Some leaf fall is normal. Gardenias drop some older leaves just before blooms appear in the spring. Maintain optimum moisture levels in the soil, moist, but not saturated. Maintain nutrient levels by frequent feedings.
SUMMARY
Properly grown and maintained, gardenias are one of the joys in the garden. The shiny green leaves and the gorgeous, white, intensely fragrant flowers are a sight to behold. Placing gardenias in the right spot in the landscape, taking care that the crown is above the native soil and using generous amounts of peat moss when planting, will give the gardenias a good head start. Prevent leaves from turning brown at the edges by keeping the soil acidic and keep those dark green leaves that way by applying iron. Insects are not a major problem and they are easily controlled with sprays.