GARDENIA for Me, Nothing Evokes Summer More Than the Fragrance of a Gardenia
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Nancy Merwin January 30, 2020 GARDENIA For me, nothing evokes summer more than the fragrance of a gardenia. My love affair with this beautiful, fragrant, classic flower began sixty years ago in my Mother’s well-tended Bay Area garden. She grew several varieties and placed bowls of floating gardenias throughout the house in summer. My favorite variety was ‘Mystery’ as it is the largest, most fragrant gardenia. As I grew older, trips to San Francisco’s Union Square often included a stop at the corner florist stand where a gardenia corsage was purchased and proudly worn. For my birthday my Father always gave me one gardenia for each year, on my 30th birthday he gave me a gardenia plant having decided it was time for me to learn to grow my own. Thus began my endeavor to grow the gardenia. History G. Jasminoides, commonly known as Gardenia is part of the Rubiaceae Family. An evergreen flowering plant known for its shiny dark green leaves, displaying white or yellowish, single or double flower with a strong fragrance. It is most commonly found in tropical and subtropical areas such as the Pacific Islands, Southern China, and Japan. In the US it grows outdoors in Zones 7-9, 12- 16 and 18-23. In other zones, it can successfully be grown in containers or a greenhouse (H1, H2). The gardenia is native of China, (where it was thought to have been around for a thousand years), Taiwan and Japan. One theory is that it was brought to England in the 1750s and may have been named after jasmine due to its fragrance. In 1761 it was brought to America where John Ellis first cultivated the gardenia in a South Carolina plantation. It is said that he named the genus after Dr. Alexander Garden, a Charleston physician. In the late 19th century it became popular for gentlemen to wear the flower in the buttonhole of a formal coat and in the twentieth century for women’s 1 | P a g e corsage and wedding bouquets. The gardenia became a valued commercial flower for florists due to the flowers' ability to keep well for several weeks in cold storage. Qualities and Varieties The Gardenia flowers outdoors usually from mid-summer to early autumn and longer in tropical climates. It can be used as stunning single planting, hedges, shaped into small tree- standards, or grown in containers. It blooms best after the first year and for the next five or so years. There are thought to be well over 100 varieties of gardenias. For our purposes, we will discuss a few varieties that can be grown outdoors in the Bay Area. August Beauty- grows 4-6 feet high and 3-4 feet wide in an erect manner and produces a loose, double white flower 2-3 inches in early summer. Aimee (or Frist Love)-grows 4-6 feet tall and wide in an upright manner and produces one of the largest, rose-like, double flowers with petals in a spiral design. It begins blooming in spring and continues through the summer. Mystery- grows 6-8 feet high and wide and can grow larger; it is one of the most fragrant gardenias with pure white flowers 4-5inches in diameter. This blooms mid-summer to early fall and may bloom longer in warmer climates and is the variety most used by florists. It needs regular pruning to keep it from becoming leggy. Radicans (Prostrata) - a miniature, compact gardenia that grows 6-12 inches high and 2-3 feet wide. This variety produces abundant 1 inch flowers in early summer and is used beautifully as an edging plant, ground cover or in a container. It also comes with variegated leaves variety such as Prostrata Variegata. Veitchii-(also known as ‘Everblooming’ Gardenia) - grows 3-4.5 feet high and 3 feet wide in a compact manner. One of the oldest varieties and very reliable bloomers, it produces a pure white flowers 1.5-2 inches that resembles a rose and blooms late spring into fall. 2 | P a g e Grafted Gardenias- In my opinion, the easiest varieties to grow in the bay area are those grafted from the rootstock of Gardenia thunbergii. This variety, a native to South Africa, is more tolerant in cooler areas and clay soil; its leaves will stay green and won’t yellow out as easily in winter. It is grafted onto August Beauty, Frist Love, Mystery, Veitchii as these are some of the best gardenia performers in our zones. These gardenias can be found at Sloat Garden Center in SF or at nurseries who buy from the grower, Monrovia. Cultivation Many believe the gardenia is difficult to grow but with the right care, it can be a very successful, show-stopping plant in our area without using a greenhouse. It is best to plant in the spring, well after all frost has passed, or in early summer. Its roots like to be kept warm and should be planted in a sheltered area, protected from frost and wind. To bloom best, most varieties need to receive full sun or at least between hours of 11 AM-2 PM (light afternoon shade only when in the hottest zones). Western exposure is the best to encourage flowering. Locating a gardenia near a door or window is always an excellent idea so its fragrance can be easily enjoyed. Planting Conditions Plant a gardenia ‘high’ in the soil as they are area surface rooting plants and need to have plenty of space around their roots- best not to plant too close to an. It is but best not to spray the plants when in the full sun or spray the buds as this can damage them. Do not overwater, keep the soil moist but not soggy, organic mulching can help maintain moist soil. Soil The gardenia grows best in cool, moist acidic soil with excellent drainage. If soil is too alkaline it causes the leaves to yellow. A planting mix for acid-loving plants is recommended. If planting in clay soil, dig a larger hole and mix some coarse sand into the planting mix. To provide the best drainage in clay soil, dig the hole 3 feet deep and fill the bottom foot with gravel before adding the mix. When plating in loam or sandy soil, dig a large hole at least 1 foot deep and 2 feet wider than rootball and 3 | P a g e fill with the planting mix for acid-loving plants or mix in equal parts of loam, leaf mold and well- decayed manure. The PH of soil is best kept between 5 and 6. Too acid a soil (PH 4.5 or lower) will cause buds to drop and too alkaline (PH above 7) leaves will become yellow as the plant will not be able to produce enough chlorophyll. Adding organic matter such as peat moss will help to increase the acidity (iron sulfate or iron chelate can be used to increase acidity as well). Usually, too much acid is not an issue, adding lime can decrease this problem. It is best to check the PH of the soil to best determine what, if anything, to add to your soil. Fertilization Use a commercial fertilizer for acid-loving plants every 3-4 weeks during the growing season, April-October. Fish emulsion or blood meal can be used instead as they are both high in nitrogen and phosphorus, however, you must be careful when using either of these as it can cause nitrogen burn. When plants receive too much nitrogen and are ‘burned’, they may appear shriveled or crispy looking. When using blood meal it is best to use the ration of 1 tablespoon per gallon of water and let stand overnight before adding to the plant to avoid burning the roots. On the other hand, if the plant is lacking in nitrogen, the leaves will look pale yellow and show poor growth. Lack of Magnesium can lead to yellow leaves with green veins; treat by adding one tablespoon of Epsom salts to a gallon of water and soak the roots and best if done in the spring. Irrigation Gardenias like moist but not soggy soil. Soil should drain fast to keep the soil barely moist as too much water can allow fungi to attack and overwatering can cause the leaves to turn yellow (along with too high a PH). Keeping the roots mulched will help the plant retain and provide more consistent moisture especially when the weather is hot. Should the irrigation water have high salt content it may be necessary to water deeply once a month. Pruning 4 | P a g e Flowers should be cut when fully open, cutting foliage with the flower may result in a reduced number of flowers it produces. As next seasons blooms develop on the new growth, prune lightly after flowering to shape and to remove dead or “straggling” branches. Remove old flowers frequently during the blooming season. Pests Gardenias fleshy foliage makes them susceptible to feeding insects such as aphids and brown scale. These feed on sap and secret what is known as ‘honeydew’ which can then create an unattractive layer of black, sooty mold on the stems and leaves. Eventually, this mold will keep light from reaching the gardenia and if sufficiently severe will stop the plant from the process of photosynthesis, resulting in stunted growth. Smaller infestations of aphids, whitefly and brown scale can be controlled by washing the plants frequently with a strong spray of water and washing the sooty mold off leaves and stems with soapy water.