Grammatophyllum is a genus of 13 currently known orchid species. The name is derived from the Greek words "gramma" (a line or streak or mark) and "phyllon" (leaf), referring to the parallel leaf veins or the markings of the perianth. This epiphytic genus occurs in the dense rainforest from Indo-China to Indonesia, the Philippines, New Guinea, and the Southwest Pacific islands.
There are two distinct growth forms in this genus. The first has very long pseudobulbs, resembling sugar cane, bearing many leaves, arranged distichous (alternating in two opposite ranks). The second has rather short thick pseudobulbs which are not covered leaf bases and bear a few leaves around the top of the pseudobulbs. The pseudobulbs are sympodial in growth, with each new growth arising from the previous growth. The flowers of most Grammatophyllum species are generally yellow and brown.
Grammatophyllums grow well in moderate light intensity. Morning sun is best, until about noon. Observation of the leaf structure can be your best guide to the correct light conditions for which a type is particularly suited. Lime green-colored foliage is an indication of proper light. Dark green foliage, while very attractive, is not conducive to the plant reaching its full blooming potential. Yellow-colored foliage indicates too much light. In very mild climates, most members of this can be grown out of doors, with protection from the hot summer sun, and the colder nights of winter.
The ideal annual temperature range for most members of the genus Grammatophyllum are 75 to 85 °F (24 to 30 °C) during the day and 55 to 60 °F (13 to 16 °C) at night. Plants will tolerate temperatures to 45 °F (10 °C) and up to 100 °F (38 °C) for short periods. At higher temperatures, air circulation and humidity must be increased, or damage can occur.
Grammatophyllums enjoy frequent watering, during their growing period, but will not tolerate wet feet for extended periods. However, when growth is completed, a 2 or 3 week rest period should follow to allow the growths to mature. Generally speaking, the growing season extends from March to October. The frequency of watering is relative to the container, the temperature, air circulation, and the amount of water retained in the medium in the container. Watering should be done, so the roots are approaching dryness before rewatering. In the warmer periods, several waterings a week can be done, without worry, if the roots can dry quickly. The roots are sensitive to fertilizer salt build-up, so clear water flushes are necessary for good growth.
Grammatophyllum plants should be fed consistently, when in full growth. During the spring through early fall, fertilizing every seven days, with several clear waterings in between, will make your Grammatophyllum plants happy. In the late fall through winter, a light feeding once a month will suffice.
The fertilizer formula should match the potting medium. Use 20-10-20 with tree fern, charcoal, or various inorganic aggregates, but use 30-10-10 with fir bark. We recommend non-urea based fertilizers at half strength. Non-urea fertilizers provide 100% immediately available nitrogen, which urea-based fertilizers do not.
Whichever formula is selected, we recommend half strength at each application. As with most Orchids, Grammatophyllum roots are sensitive to fertilizer salt build-up. Grammatophyllums are particularly fond of organic fertilizers, such as fish emulsion and manure teas. The organic fertilizers eliminate the concern of salt build up in the medium.
Grammatophyllums do not resent being disturbed, so repotting should be undertaken whenever necessary. The best time is, after all, flowering has ceased, and new growth is just beginning. To minimize root damage, a warm water soak for 10 minutes, will make most roots very pliable and easier to remove from the container.
While most Grammatophyllums will do well in clay or plastic pots, some large-growing types such as Grammatophyllum speciosum are best grown in a wire or wooden basket. The strong, rapidly-growing root system often breaks ordinary pots. The baskets allow free airflow over the roots and eliminate over watering problems.
The potting medium must be well-drained, i.e., coarse fir bark, lava rock, pieces of broken pottery, chunks of tree fern, hardwood charcoal, etc. so that the roots can be wet, but then dry quickly.
When dividing Grammatophyllum plants, always divide into parts with at least four pseudobulbs. Remove any dead roots from the divisions, then lay the divisions aside until new root growth begins. At that time, usually a week or so, repot the divisions in their new pots. Now the plants can be watered and fertilized as usual without worrying about rotting them because they retained no roots in the division. Newly repotted plants should be placed in slightly lower light for several weeks.