Monday, August 30, 2010

Gerbera Daisies by Gardener Dave

With their large, bright, color-crayon-colorful “Daisy” flowers, wide “spinachy” leaves and upright attitude, healthy Gerberas, Gerbera jamesonii (hybrids) are an asset to the garden in beds or in pots.  They are rated by some nurseries as “Impulse Buys”, due to their showy nature.  Ooookay!  Sure, I can grow those – they look so healthy and easy!  I can accept that they are an annual here!

To be brutally honest, I’ve never had a lot of success with Gerbera’s.  For me, they either burn from too much of our high-altitude sun, or they get powdery mildew on their broad leaves (lots!), or they just quit blooming, or all of the above.  I think I have concluded that they can be “touchy”!  Soooo… having now done some more research, I am trying them again this late summer season, starting with 4”potted, brightly-colored, healthy ones, bought at reduced prices.  I will treat them per my newfound advice and see what happens. I am inviting your comments re: experiences you have had with them, maybe we can all learn something about growing these spectacular flowers!

 My Summary of Cultural Information from Various Sources:

Things to avoid
  • Wet, poorly drained soil
  • Crowns below soil level
  • Hot (especially afternoon) sun
  • Pests: Thrips, leaf miner, spider mite, caterpillar, botrytis, powdery mildew, fungal rot and crown rot.
More Tips - From Greenhouse Growers
  • Light - Gerberas require high light intensities for good-quality plants and high flower bud numbers... Plants receiving too little light have pale green, stretched foliage and long, weak flower stems. Plants receiving too much light have compact, slightly yellow foliage with short flower stems often hidden in the foliage. (Morning sun or filtered sun is best in our location).
  • Watering - Gerberas should receive a thorough watering and then be allowed to dry somewhat. This discourages soil-borne diseases. Gerberas should never be allowed to wilt, however. Plants allowed to dry out too much and too frequently have short flower stems that may be hidden in the foliage. It is also a good practice to water early in the day so the foliage is completely dry before evening.

  • Diseases - Powdery mildew, Phytophthora (crown/root rot), Botrytis, impatiens necrotic spot virus, and bacterial blight are the main disease problems of gerberas. (Do not overcrowd plants).
Typical Greenhouse Culture: Indirect or filtered sun, with well-drained soil mix. Many greenhouses use a soil mix consisting of 2 parts peat moss to 2 parts sand to 1 part loam. During the growing and blooming seasons, the plants are watered and allowed to dry slightly. Too much water can cause crown rot. Plants are fertilized monthly with a balanced fertilizer, especially during blooming. Spent flowers should be trimmed off. Crown rots and many fungal vectors can attack the plant if they are kept too wet.
Some Common Problems and Probable Causes
  • Foliage too large or flower stems too long:
    • Light intensity too low
    • Ammonium fertilizer too high
  • Flower stems too short:
    • Plants too dry
    • Soluble salts too high
    • Growing temperature too cold
  • Flowers distorted:
    • Mite or thrips problem
    • Soluble salts too high
    • Temperature too high or too low
  • Plants stunted or failing to grow:
    • Drainage or aeration poor; plants too wet
    • Soil temperature too low
    • Plants planted too deep
  • Plants wilting or dying:
    • Plants planted too deep--crown rot develops
    • Root rot
Other Gerbera Observations from Various Sources - Since Gerberas have been extensively hybridized, they may occasionally exhibit some “eccentricities” such as distorted flowers or leaves – however, newly sprouted leaves or flowers can be entirely normal on the same plant. (I was going to make a comparison with King Tut’s ancestry here, but I won’t.)  Flowers that are blooming on the plant when purchased will frequently wilt or die when plants are transplanted to new locations/environments. Newly sprouted flowers should be OK.

Historical Background…  (If you’re interested enough to care. This came from several online sources)
Common Names: Gerber daisy, Transvaal daisy, Barberton daisy, African daisy
Family: Asteraceae/Compositae (aster/daisy/sunflower family)
Gerberas have approximately 30 species in the wild, extending to South America, Africa and tropical Asia.  They were discovered by Scotsman Robert Jameson in the 1880’s near Barberton, South Africa. It was named in honor of the German naturalist Traugott Gerber, a friend of Carolus Linnaeus, who is known as the father of modern taxonomy (sorry, no connection to the Gerber baby food company).  Jameson donated plants to the Durban Botanical Gardens, and the curator of the gardens, John Medley Wood, sent specimens to Harry Bolus in Cape Town, South Africa, for identification. Bolus then sent specimens to the Royal Botanical Gardens at Kew in England, with the suggested scientific name Gerbera jamesonii.  Beginning about 1890 in England, Richard Irwin Lynch carried out breeding programs that resulted in many improvements. Gerberas soon became popular in the Netherlands, where much of the modern breeding has been accomplished. Gerberas were not produced in North America until the early 1920s. Extensive breeding at the University of California at Davis during the 1970s led to many plants suitable for garden use. However, breeding in Florida and Europe focused on developing long-stemmed cultivars for greenhouse cut flower production. In fact, much of the production today in Europe and Japan is for cut flowers.
In the U.S., California and Florida are the leading states in the production of cut flowers and tissue-cultured stock. The majority of cut gerberas, however, come from Columbia and surrounding countries in South America, with substantial quantities coming from the Netherlands. Current breeding strives for vigorous growth, compact habit, and continuous flowering on sturdy stems. The domesticated cultivars are mostly a result of a cross between Gerbera jamesonii and another South African species, Gerbera viridifolia. The cross is known as Gerbera hybrida. Thousands of cultivars exist. They vary greatly in shape and size. Colors include white, yellow, orange, red, and pink. The center of the flower is sometimes black. Often the same flower can have petals of several different colors. It is the fifth most-used cut flower in the world (after rose, carnation, chrysanthemum and tulip).  Gerberas are attractive to bees, butterflies and birds, and are resistant to deer.
Gardener Dave