Media
Page 21 (contributed by Ken Leonhardt, Edwin Mersino, and Kelvin Sewake)

"The primary purpose of a planting medium is to provide support for the plant and a healthy environment for root development. The root system is of critical importance because its function is to absorb and assimilate nutrients and water. A poorly developed or poorly functioning root system cannot take up adequate nutrients and water to support healthy plant growth and acceptable flower yields."

"The parent species of modern dendrobium cutflower hybrids are epiphytes in their native habitats. They grow clinging to trees and rocks where drainage and aeration are optimal. They are not found growing in the soil or forest litter. Growers must attempt to simulate such good drainage and aeration conditions in cultivation. For a cutflower grower, repotting mature plants is impractical; thus the growing medium must provide good drainage and aeration for the entire productive life of the plant."

"The most widely used growing medium throughout Asia for cutflower production stock is coconut husk and fiber in one form or another. This is satisfactory only for short-term cultivation. The fibers of the coconut attract and retain water, but within two years the medium partially decomposes and begins to restrict drainage and aeration. Within three years, anaerobic conditions may result in root tissue breakdown and conditions favoring diseases. Three flowering cycles is all that Asian growers expect from their plants."

"In contrast to Asian practices, the Hawaii grower expects seven to ten years of production from cutflower plants without repotting them. The Hawaii grower must therefore use an inorganic medium that resists decomposition. Plants can be grown on the ground in beds or in containers, or on a strong low bench. The preferred medium in Hawaii is basaltic gravel, known locally as "blue rock" (Fig. 2.4, 2.5). It should be screened to stones ranging in size from 1½ to 2¼ inches referred to by quarry processors as "number 3" size. It is important to remove the smaller stones and fine particles that would impede drainage and aeration after roots have penetrated and occupied the spaces between aggregates. Basaltic gravel is readily available, inexpensive, durable, and has high porosity. However, it has a low nutrient-holding capacity, and te plants will require a continuous nutrient supply."

"Producers of dendrobiums for local potted plant sales also use blue rock, but it is usually screened to a smaller size. Potted dendrobiums shipped out of state are often grow in lighter media, such as peat and perlite mixes. Shredded coconut husks, cubed coconut husks, Styrofoam and other light materials are also used for these plants."

"Another suitable medium is volcanic cinder, which is lighter than blue rock, has greater surface area due to its irregular form, and provides adequate drainage and aeration for short-term production purposes such as potted plants. Volcanic cinder is more widely used on the island of Hawaii, where it is available locally."

Spacing
Page 22 (contributed by Ken Leonhardt, Edwin Mersino, and Kelvin Sewake)

"A wide range of planting densities is used for dendrobium cutflower production. In earlier times, up to 35,000 plants were planted per acre. It was learned, however, that as the plants grew larger, the dense tangle of canes prevented good airflow. This hindered adequate penetration and coverage of pesticides, and insect and disease control became a problem. It also resulted in a high percentage of bent, unmarketable sprays."

"Currently, the common practice is to plant between 15,000 and 22,000 plants per acre. Any number of patterns can be used for laying out the planting beds (Fig. 2.6, 2.7). The spacing of the beds and aisles depends on the spacing of the shadehouse supporting members, the length and width of the structure, and other infrastructure conditions. Typically, aisles are not less than 4 ft wide, and beds are 4 - 5 ft wide. The spacing of the plants in the beds is determined by the size of the bags or pots (if they are used), the size of the beds, the predicted life span of the plants, the availability of plants of appropriate size, and the plant density required."

"A high density of plants means a higher initial cost for planting material and a higher initial return from production. This must be balanced with the longer crop cycle of a less dense planting. The lower the plant density, the longer the potential crop cycle. However, a lower density means that the grower has to wait longer before the crop reaches its peak production in terms of yield per area. Factors such as cost-recovery time for the capital investment need to be considered. Every grower has a unique situation, and the decision must be based on it."

Irrigation
Page 24 (contributed by Ken Leonhardt, Edwin Mersino, and Kelvin Sewake)

"Dendrobiums must be irrigated for optimum production, especially during dry periods. Since dendrobiums are grown in porous media that holds little water, they should be irrigated whenever the media and root mass become dry. In dry, hot areas with basaltic gravel as a media, daily irrigation may be necessary. In humid, cooler areas, irrigation may be done once to three times per week, depending on the season and weather."

"The common practice at present is to mount rotating sprinkler heads above the plants. This practice encourages the spread of foliar diseases. It is better to design an irrigation system to apply water to the root system and keep the foliage dry. Spitters mounted on risers 12 - 24 inches above the ground can accomplish this. In addition, this type of system conserves water because irrigation water can be directed only to the plants, and aisles and peripheral areas can be kept dry (Fig. 2.8). Drip irrigation is seldom used because the large pore spaces of the most commonly used growth mediums do not allow capillary action to wet the entire root mass."