Anthurium

 Anthuriums have been cultivated for many decades for cut flower production. Since the mid 1980’s, Anthurium’s popularity as a flowering pot plant has increased dramatically and has become a popular addition to many foliage growers’ product lines. Anthuriums are relatively easy to grow, have attractive foliage and under the proper environment, produce long lasting flowers year round. Currently, numerous cultivars with different flower sizes, shapes, colors and some with delicate fragrances are available for the consumer. Commercially, Anthuriums are grown throughout the world with the heaviest concentrations in the United States (Florida) and The Netherlands.

Anthuriums can be divided into four basic groups; A. andreanum cultivars, inter-specific hybrids between A. andreanum cultivars and dwarf species currently referred to as ‘Andreacola’ types, A. scherzeranum hybrids, and foliage Anthuriums. Anthurium andreanum, a generally large, somewhat open-structured plant with large flowers, is commonly grown for cut flower production and sometimes adaptable to pot culture. New andreanum cultivars, selected specifically for pot culture are more compact. A. andreanum primary flower colors are white, pink, red, red-orange and green. ‘Andreacola’ cultivars are small to intermediate in overall size, fuller, more compact and generally produce smaller but more numerous flowers than andreanum cultivars. ‘Andreacola’ cultivars tend to have thicker, dark green leaves and many times show resistance to the more aggressive Anthurium diseases. Primary flower colors are white, pink, red and lavender. A. scherzeranum, the first widely cultivated Anthurium pot plant, is a small, compact plant. Primary flower colors are white, pink and red. Foliage Anthuriums come in numerous shapes and sizes and represent a minor portion of the total Anthurium pot market. However, it should be noted that most foliage Anthuriums are durable plants and offer the consumer distinct forms.

Most Anthurium species are native to tropical rain forests and are primarily epiphytic in nature. Thus, in their natural habitat, they receive ample, frequent water with good drainage. In cultivation, Anthuriums prefer evenly moist media especially when actively growing. Overall, it is better to slightly underwater than overwater. Drying out may cause tip burn, root damage and reduced growth rates while over watering can also cause root damage and sudden yellowing of older leaves. Anthurium will not tolerate saturated, poorly drained soil mixes. Best results are achieved with a 1:1:1 ratio of Canadian peat, composted pine bark (watch for particle size; not too much dust) and perlite or airlite. Avoid vermiculite except in 4″ (10cm) containers. In long-term crops, i.e., 6″ (15cm) and up, vermiculite compacts and will water-log. Soil pH should be maintained between 5.5 and 6.5.

Young plants are primarily propagated by tissue culture and available commercially as 72 or 98 cell liner trays. Depending on the cultivar’s inherent branching and flowering habit, young plant producers use one to three plants (microcuttings) per liner cell. Cultural conditions, especially light intensity, are very important for young plant production. Finish growers should avoid using young plants grown under low light conditions.

Most pot Anthuriums are sold in 6″ and 8″ (15-20cm) containers, with a smaller percentage in 4″ and 10″ (10-25cm) containers. Crop finish times will vary depending on cultivar, pot size and cultural environment. Except in the case of scherzeranum, growers should consider Anthurium a long term floral crop. Under the sub-tropical climate of Florida, most 6″ container crops are finished in 8 to 10 months, using 72 or 98 cell tray young plants. Scherzeranum is usually grown in 3 1/2 to 6″ (9-15cm) containers and will finish in 4 to 7 months. A young plant supplier will be able to give recommendations on the optimum container size and finish times for each individual cultivar.

Moderate but consistent levels of a complete fertilizer are important. Magnesium requirements in Anthurium plant tissue are higher than most foliage crops especially in warmer climates. Because of the long-term nature of Anthurium crops, special attention must be paid to ensure continued availability of Magnesium. Per cubic yard of soil, incorporate 10 lbs. (4.5kg) of dolomite and 3 1/2 lbs. (1.6kg) Hi-Cal lime to balance the Calcium and Magnesium ratio. Regular foliar applications of Magnesium sources (Epsom Salts, Magnesium Nitrate, etc.) will help prevent Magnesium deficiencies. After 24-26 weeks, a top-dressing of dolomite (3 tbsp/10″ pot) or another Magnesium source will help insure continued availability of Magnesium. Top-dressings of Epsom Salts are beneficial but short-lived.

Avoid high nutrient levels especially after planting young plants. Liquid fertilizer on a constant feed program should not exceed 250 ppm Nitrogen (N). On mature plants, occasional rates as high as 400 ppm N are acceptable, but must be alternated with watering. Tests have shown that plants given frequent doses of 300-400 ppm N grow slower, have lighter flower colors and produce thick deformed leaves. When using overhead irrigation system to dispense liquid fertilizer, a quick rinse with pure water is beneficial since liquid fertilizer left on foliage can damage leaves causing grayish corky scars. With dry fertilizer applications, it is very important to water frequently to reduce salt build-up. When using time-release fertilizers, carefully consider crop times and if necessary reapply to avoid deficiencies.

Anthuriums grow best with day temperatures of 78 to 90°F (25-32°C), and night temperatures of 70 to 75°F (21-24°C). Temperatures above 90° F may cause foliar burning, faded flower color and reduced flower life. Night temperatures between 40 to 50°F (4-10°C) can result in slow growth and yellowing of lower leaves. Scherzeranum cultivars require lower temperatures in the range of 68 to 80°F (20-27°C) daytime and 60 to 70°F (15-21°C) nights. Anthuriums will not tolerate frost or freezing conditions.

Anthuriums grow under a wide range of light intensities but their actual performance is dependent on the cultivar, elevation, temperature and nutrition. Generally, most Anthurium types grow well at light intensities ranging from 1,500 to 2,500 f.c (1627klux). Light intensities higher than 2,500 f.c. (27 klux) can result in faded flower and leaf color. Scherzeranum cultivars are best grown at light intensities between 1,000 and 1,500 f.c. (11-16klux).

Preventive maintenance programs for mites, snails, slugs, worms, thrips and white flies are important. White flies are especially attracted to the new growth and once established are difficult to eradicate. A number of chemicals are effective for pest management, however, cultural conditions and cultivars will determine what you can use safely. Many growers have experienced phytotoxicity on numerous Anthurium cultivars from the use of certain pesticides. Never apply pesticides while plants are under any form of stress, i.e., moisture or hot temperatures.

Anthurium blight, caused by Xanthomonas campestris pv dieffenbachiae, is by far the greatest challenge to the anthurium grower. While many of the pot type varieties (specifically the ‘Andreacola’ varieties) are resistant or partially resistant, many of the hybrids with larger, showier flowers have no resistance. Xanthomonas is a bacterium. The pathovar Xanthomonas campestris pv dieffenbachiae is specific to plants in the Araceae family and is most pathogenic on Dieffenbachia, Aglaonema, and Anthurium. The disease can easily spread from one genus to another in this group. Syngoniums and pothos also have the potential to host strains of Xanthomonas which may be pathogenic to Anthuriums.

There is no available chemical cure for Xanthomonas blight. While some chemicals are effective as a preventive measure, none of the fungicides/bactericides in the market today will actually cure an infection. Thus, the only effective way of controlling blight is via sanitation and prevention.

Virtually all of the pot type Anthuriums in the market today are produced from tissue culture. As plants will not survive in vitro infected with Xanthomonas, plants directly harvested from tissue culture can be considered free of infection. However, young plants weaned in the greenhouse are susceptible to infection. The same sanitation practices should be in place in young plant production as those practices effective in finished production.

Since Xanthomonas can exist in plants without any visible symptoms, it is wise to isolate incoming plant material for observation before introducing into the production facility. Proper cultural practices and sanitation can be effective in prevention and spread of blight.

Cultural practices:

Keep foliage dry if possible. Drip irrigation and hard cover are essential when growing susceptible cultivars. Lower humidity will decrease guftation and can help dry the foliage faster if using overhead irrigation. Give plants ample spacing to allow for good air circulation. Avoid condensation with the use of fans. Avoid hanging plants above your Anthurium crop. High Nitrogen fertilization makes plants more susceptible to infection. Preventive maintenance programs of Copper based fungicides alternated with bactericides of streptomycin or oxytetracycline can help prevent infection. However, Copper can be phytotoxic to many cultivars!

Sanitation:

Disinfect all benches, pots, and tools coming in contact with plant material. Prevent standing water under benches. Routinely (preferably daily) rogue out any infected plants. This is most effective at the end of the day. Do this when foliage is dry and remove all infected plants and plant parts from the greenhouse premises. Avoid any unnecessary movement through aisles. Avoid cross-contamination by isolating susceptible crops. Aglaonemas imported from the tropics are frequently carriers. Inhouse vegetative propagation of Dieffenbachia and Aglaonemas should be kept far from tissue cultured plants.

Many Anthurium cultivars are susceptible to Phytophthora, Rhizoctonia, Pythium, Colletotrichum and Pseudomonas. Although there are a number of effective fungicides for these diseases (we have not seen phytotoxicity from proper use of the popular chemicals available), the best approach is prevention via cultural practices. Keep plants off the ground, provide good ventilation and avoid overhead irrigation during late afternoon or evening hours. As a matter of caution, all new pesticides should be used in a controlled test on a small percentage of each cultivar grown. Always allow four weeks for phytotoxic symptoms to appear. Most often, symptoms occur as distortion and/or discoloration of new growth.

Since their introduction, potted Anthuriums have generated a great deal of excitement at retail and with the end user. Anthuriums are durable and will survive as an indoor foliage plant for a remarkable period of time, even under adverse conditions. The big plus, of course, is the added canopy of color. If the last few years are any indication, Anthuriums as flowering pot plants will continue to grow in popularity. As a result of breeding programs, new and improved cultivars will be introduced which will help Anthuriums gain additional market share.

This text is a recommendation only; it is not an endorsement of any products or acceptance of any liability as a result of usage.

Update: 2.16.2012