AOS Stanhopea Culture Sheet

Stanhopea and Relatives

Stanhopeas bear incredible flowers with intricate and complex structures and mechanisms for pollination, from channeled "walkways" for insects, to buckets of a watery solution. Most have inflorescences that grow downward, so the plants must be potted in hanging baskets or similar containers. Flowers may be spicily fragrant, and although the flowers are short-lived, each plant may produce many inflorescences throughout the year.

Related genera, Paphinia and Peristeria, grow cooler and warmer, respectively, than others in this group, and produce upright inflorescences.

LIGHT should be bright, with direct sunlight diffused so as not to burn the leaves. Most growers suspend these orchids due to their pendulous inflorescences. This also brings the plants closer to the light. Light levels approximating those for cattleyas, or 3,000 foot-candles, are best.

TEMPERATURES for these orchids should be moderate: 52 to 60 degrees F at night, with day temperatures 68 to 75 degrees F in the winter. Plants can stand short spells of higher temperatures, but air movement, humidity and shading must all be increased. Cool night temperatures seem to promote flowering. Many species flower in the summer, and putting them outside in the summer may be ideal.

WATER in ample quantities is important to produce strong pseudobulbs and healthy flowers. Most growers pot in an open medium and water frequently, especially when warm. Dry roots lead to leaf-tip dieback, or a browning of the leaf tip. Watering frequency can be reduced in the winter months, but these plants should never dry out completely.

HUMIDITY should be kept at 40% to 75%, and at high levels especially when temperatures are high. Frequent misting reduces the chance of mite and insect infection; at the same time, strong air movement must be provided to prevent spotting of the foliage.

FERTILIZER should be applied at regular intervals. Most growers fertilize with a diluted concentration every week to two weeks. For plants in bark, use a 30-10-10 high nitrogen formulation, alternating with a 20-20-20 balanced formulation; in the blooming season, which is mainly summer, use a 10-30-20 bloom booster formulation. Plants grown in osmunda need fertilization only infrequently.

POTTING is best right after summer bloom, as most plants seem to grow year-round. Plants that rest in the winter may be repotted in the spring. The best flowerings come from large clumps of plants, so large baskets are usually used. An airy, yet moist medium seems to work best, such as medium-grade fir bark (often mixed with sphagnum peat) or osmunda fiber. Baskets are most often lined with moss before plants are placed in the medium; this allows the pendulous inflorescences to grow through the bottom of the basket. Pre-moisten the potting medium so that the roots do not dry severely after repotting. Vigorous plants may need repotting every three years.

Prepared by: Education Committee, American Orchid Society, 6000 S. Olive Ave., West Palm Beach, FL 33405 (407) 585-8666.