National Garden Bureau, the non-profit organization promoting gardening on behalf of the horticulture industry, is pleased to announce the three crops that will be featured in their 2013 "Year of the" program. They are Gerbera for annuals, Wildflowers for perennials and Watermelon for edible vegetables. This week, we will focus on the Gerbera…
Few flowers capture the hearts of people more than Gerbera Daisies since the daisy shape is such a familiar form and is easily drawn by artists of all abilities. Combine the pleasing shape of Gerbera with bright luminous colors and you have an irresistible plant for today’s gardens. Gerbera is an extensive genus and a member of the sunflower family (Asteraceae). There are approximately 30 species in the wild, extending to South America, Africa and tropical Asia. The meanings of Gerbera flowers come from those attributed to the general daisy family. These meanings include innocence and purity. The daisy is also a classic symbol of beauty. In addition, Gerberas hold an added meaning of cheerfulness, which stems from the assortment of colors available.
Gerbera, as we know it today, probably originates from crossings between Gerbera jamesonii and Gerbera viridifolia. Both of these species are native to the southern part of Africa, in particular South Africa. The Gerbera genus was classified in 1737 by Gronovius and named after the German botanist, Traugott Gerber, who travelled extensively in Russia and was a friend of Carolus Linnaeus. In 1884, a rich gold deposit was discovered near Barberton, South Africa. Robert Jameson, a Scottish businessman, formed a mining company to search for gold in the Barberton area in the Kaap Valley. Near the mining operation wild Gerbera plants grew in profusion. Mr. Jameson, an amateur botanist, took interest in the wild Gerbera plants and brought some plants back with him when he returned to his residence in Durban, South Africa. These plants would later become known as the Transvaal or Barberton Daisy. The plants were initially given to the local Botanic Garden in Durban and then in 1888 sent to Kew Gardens in England. Only one plant survived the journey but fortunately another botanist, Harry Bolus, had previously sent a large number of plants to Kew in 1886 and suggested naming the species after Robert Jameson. The lead botanist at Kew, Joseph T. Hooker, agreed and soon work began in England on the development of the modern Gerbera.
In the beginning of the 20th century, the breeding of Gerbera accelerated when a large range of crosses were made by Adnet in France and Lynch in England. However, during the two world wars, not much breeding was done but in the early 1970’s the breeding of Gerberas accelerated again. Cut Gerbera were the main interest, but Gerbera for bedding use were also developed. Then in the late 1970s, breeding of potted plants began. The first gerbera for potted plant usage began with the release of Gerbera jamesonii ‘Happipot,’ an open pollinated series bred by Sakata Seed Corporation, in Yokohama, Japan. ‘Happipot’ was available in five colors and was a big hit with consumers who had never seen daisy-type flowers in colors other than white. In the early 1990s, Sakata improved on the ‘Happipot’ series with the introduction of the world’s first F1 hybrid pot Gerbera series, ‘Skipper’ and ‘Tempo.’ ‘Skipper,’ was a mini type for 4-inch/10 cm pots and ‘Tempo’ was bred for slightly larger pots. In the late 1980s, Daehnfeldt Seed Company, based in Odense, Denmark, raised the bar with the introduction of Gerbera ‘Festival’ series. ‘Festival’ offered bright colors in an expanded color range. Initially, all Gerbera were available with green centers, but in the mid-1990s, Daehnfeldt released varieties with dark centers which added a new dimension to Gerbera, which increased its appeal. Additional flower forms, such as semi-double and spider types, were later introduced to pique the consumer’s interest and offer more beautiful flower forms.
Gerbera species bear a large flower head with rayed petals in pink, orange, yellow, gold, white, red, cream and bi-colors. The center of the flower is either green or black. The flower head has the appearance of a single flower but is actually composed of hundreds of individual flowers. Gerbera flowers are diverse, and their flower heads range from 2.5 to 8 inches/6–20 cm in diameter. Single flowers: The main class of flowers is the single type with two layers of flower petals. Semi-double flowers: The semi-doubles are often seen in cut flower types and some series of pot types. Semi-double flowers have extra rows of mini petals around the center eye, giving the blooms added bulk and interest. Double flowers: Unique full flowers have 5-7 layers of flower petals that completely cover the flower head. Spider flowers: Featuring a unique flower form with thinner and more pointed flower petals resembling sea urchins.
Many consumers have their first encounter with Gerbera as cut flowers since Gerbera is the fifth most used cut flower in the world (after rose, carnation, chrysanthemum and tulip). Gerberas as cut flowers offer a rich color palette and beautiful flower forms from single to semi-double.
Originally, pot-type Gerberas were grown from seed. This changed when an outdoor patio type from tissue culture called Gerbera jamesonii ‘Giant Spinner’ was introduced. It offers enormous pink and white flowers (8-inches/20 cm) with a vigorous plant habit suitable for 10-inch/25 cm pots. Additional vegetative lines from tissue culture soon followed. Florist de Kwakel B.V. introduced the ‘Landscape’ Series, a cross between potted Gerbera and cut flower types, with large flowers targeted for patio pots and large tubs. These larger flowers met a consumer need for home-grown Gerbera cut flowers. The ‘Garvinea’ series is another recent introduction that has a more botanical-look with an abundance of smaller flowers on disease resistant plants.
It is not surprising that consumers would want to enjoy Gerberas in mixed containers throughout the summer growing season. Gerberas do well outdoors if given the proper care and conditions.
Media: Plant in coarse, well-drained media that is slightly acidic pH 5.5 – 6.5. A high pH results in iron chlorosis characterized by yellow striping of the upper foliage. A pH below 5.5 causes excess manganese to accumulate in the lower foliage characterized by black spotting or patches.
Exposure: Gerberas require morning sun in warmer southern climates and full sun in cooler northern locations. Do not plant them against a brick wall or near surfaces that reflect intense heat.
Moisture: Water early in the morning to allow rapid drying of foliage. Allowing moisture to remain on the leaf surface overnight invites diseases like powdery mildew.
Fertilizer: Incorporate a slow release fertilizer into the media and supplement with a liquid fertilizer every two weeks.
Flowering: Gerberas flower based on the amount of light the plant receives into its center. Remove excess foliage from the center throughout the season to maximize light penetration and flower production.
Diseases: Gerberas are subject to various root rots so allowing the media to dry slightly between watering aids in keeping the root system healthy. However, do not allow the plants to wilt severely as this damages the root system making it more susceptible to fungal pathogens.
Powdery mildew appears as whitish spots that quickly spread until the entire leaf surface is covered. The white powdery growth is a fungus that over time becomes gray to tan/brown felt-like patches. Leaves may become stunted, curled, chlorotic and eventually wither and dry up.
Conditions of moderate temperatures and high humidity (>80%) help develop the disease. Under warm days and cool nights, water condenses on the leaves allowing spores to germinate. Mildew pathogens are host specific, and the mildew that attacks Gerbera Daisies will not spread to melons or zucchini.
Prevention and control: The use of baking soda is a kitchen remedy that helps control powdery mildew but will not eliminate it. Mix 1 tablespoon each of baking soda and horticultural oil (dormant oil/vegetable oil) or a few drops of liquid soap to 1 gallon of water. Spray weekly making a new mix each time. It will not eliminate the disease but helps to control it. Be sure to water the plants the day before and do not apply in full sun. As always testing the plant’s sensitivity by applying to a small area first is best. Neem oil is also effective in controlling infections of powdery mildew. Mix 1 oz (2 tablespoons) of Neem oil and an approved spreader sticker or a few drops of dishwashing soap to one gallon of water. The spreader sticker causes the solution to form a film on the leaf surface as opposed to droplets. Spray once a week for two weeks. A rotation of Neem oil and baking soda is the safest control method. If using commercially available fungicide sprays, always follow label directions to make sure the product is approved for specific plants. Early detection works best. Once the disease takes hold, it is difficult to control.
-Remove the infected leaves
-Do not crowd the plants
-Provide good air circulation
-Keep plants well watered and stress free
-Grow resistant plants when available
-Avoid excess nitrogen application as succulent new growth is more susceptible.
Insects: There are several insects that attack Gerberas including aphids, whiteflies, thrips, spider mites and leaf miners. Aphids are insects that eat the sap from gerbera daisy leaves, which causes the leaves to turn yellow. Ladybugs and spiders are the aphid's natural predators. You can spray a soap solution on the leaves of the gerbera daisy to keep aphids away, or apply an insecticide for aphids from your local garden supply store. Whiteflies also eat plant juices and saps and lay eggs on the underside of the leaves. The best way to control whiteflies is spraying insecticide not only on the top, but on the underside of each leaf of your gerbera daisies. You should also avoid planting healthy plants next to infected ones. Thrips cause damage by eating leaves and also act as vectors bringing diseases from other plants they have previously eaten. Thrip infestation can also cause the flowers of the Gerbera daisy to have a distorted shape. Green lacewings are a natural predator, or you can use a soap shield to get rid of thrips. Spider mites damage gerbera daisies by sucking the sap from their leaves to the point where the leaf yellows or even drops off. Like many other gerbera daisy pests, the predators for spider mites include lady bugs and pirate bugs. GROWING GERBERAS FROM SEED
Most gardeners find it easy and convenient to purchase finished plants at the garden center. However, growing Gerberas from seed is a fun exercise for the entire family and allows the hobbyist to order some unique varieties not readily available at garden centers. Below are some basic tips to consider when deciding if this is worth doing.
-Select a lightweight, sterile and well-drained media consisting of peat moss, perlite and vermiculite. The soil should retain sufficient moisture to germinate the seed but not be saturated. Optimum pH is 5.8-6.2. -Place the media in flats or pots that have drainage holes. Make shallow rows in the flats about twice the depth of the seed’s diameter and cover lightly with extra media or coarse vermiculite. Another option is to use peat blocks or Jiffy pots, but be sure to guard against planting too deep. -Moisten the media thoroughly, but do not oversaturate so that water does not ooze when pressed with your thumb. -Cover the flats with a clear plastic germination dome or clear plastic wrap and place about 18 inches/46 cm under fluorescent lights. -Check the flats daily to ensure that there is sufficient moisture and do not allow the media to become dry, especially when Gerbera seeds are beginning to germinate. -Once seedlings emerge and the cotyledons are up and lying flat, allow the media to dry down in between watering. A lack of oxygen at the root level results in gnarled and stunted seedlings. Transplant as seedlings begin to touch to avoid stretched and spindly plants. -Gerberas do best with a calcium nitrate-based fertilizer that also contains some magnesium. Formulations such as 15-5-15 Cal/Mag at 150-200 ppm Nitrogen are ideal. Alternate as needed with an acidic formulation such as 20-10-20 to control the pH. A pH above 6.2 results in microelement deficiencies, especially iron and boron. A pH below 5.5 increases uptake of manganese with black spotting beginning on the lower foliage. Supplemental applications of magnesium applied every 14 days promote healthy green plants. Dissolve 1 teaspoon of Epsom Salts (magnesium sulfate) into 1 gallon of water or combined with a gallon of fertilizer solution. Professional fertilizer formulations are available at some garden centers or may be purchased on line. -Provide light up to 14 hours per day. Lighting longer than 14 hours causes excessive plant stretching. -Gerberas flower based on the amount of light received into the plant crown. Depending on conditions, flowering occurs in 18-20 weeks from sowing. A hobby greenhouse or sunny windowsill that provides higher light levels will hasten plant development and flowering.
Founded in 1920, the National Garden Bureau is a non-profit organization whose mission is to disseminate basic instructions for home gardeners. NGB publishes and sponsors “Year Of The” fact sheets annually featuring flowers and vegetables, including new introductions, which are especially suited to home gardens. http://www.ngb.org/
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