Vivi's Orchid Corner

Dear Orchid Friends:

Dendrobium aggregatum is one of the Callista species and is native to Burma, northern India and southern China. Other species in the Callista family include: Den. chrysotoxum, Den. densiflorum, Den. farmeri. These are classified as dwarf dendrobiums. They do not grow into tall canes but have short spindle-shaped pseudobulbs bearing thick, leathery leaves. These orchids like to be mounted on bark or cork. Dendrobium aggregatums are 'evergreen', which means they do not drop their leaves as some of the tall cane dendrobium orchids.

Care Tips: Dendrobium aggregatum definitely require a change in the cultural requirements at various times of the year and become dormant in the fall through winter months. They should be suspended and mounted on bark or cork for optimal growth. Grow them with your cattleyas (intermediate to warm conditions) but they require somewhat cooler temperatures during the winter months. In the winter move them to a cooler location and provide them with cooler night temperatures and dry conditions. Good air circulation is necessary.

Light: Dendrobium aggregatum takes high light, so keep them with cattleyas.

Watering: Watering is a crucial element for this orchid. (and may be the most difficult regimen to follow!) During spring and summer, water well when growth is developing. Be generous with your watering and fertilizing. As Autumn approaches, it is important to cut back on your watering and fertilizing schedule. Dendrobium aggregatums require dry conditions in the winter. During the fall and winter, water your plant only enough to keep the pseudobulbs from shriveling and dying. Be aware that the pseudobulbs will become wrinkly during this dormant period. You will need to learn the distinction between what is considered wrinkly and when the orchid will need some water to keep it from dying. Don't fertilize at this time. This severe drying and rest period is difficult to do especially if you are heavy handed with the water or if you are more accustomed to watering. But stick with it!

As Spring arrives and flower buds begin to emerge, increase your watering schedule. Water well while flowering and with the signs of new growth. As late Spring and Summer progress, increase watering and water thoroughly. If the tips of the leaves begin to brown, reassess how much fertilizer you are providing. Perhaps the concentration is too high and the leaves are experiencing some fertilizer burn. Or try changing your watering schedule. Determine how your orchids respond to any regimen you have established and be flexible to change if needed.

Flowers: Flowers usually appear Spring to Summer and is dependent upon adequate light. The Dendrobium aggregatum orchids form hanging clusters (like grapes) of yellow-orange flowers. The flowers are truly delightful. Flowers are approximately 1 inch in diameter, are flat with round lips. Flowers are delicate and cascade gracefully. Flowers last approximately 1-2 weeks.

Miscellaneous: Watch for spider mites. They love to live among the pseudobulbs. Spider mites are difficult to rid and will suck the life and energy out of the plant. If your plant takes a downward turn, begins to yellow, check carefully for any infestation.

Dendrobium aggregatum does necessitate a considerable change in their care in order to produce flowers. They need a solid rest period. Dendrobium aggregatum is a difficult orchid for a novice grower. It is truly difficult not to water! It took me two years to finally get it right! If it is not flowering for you, try something a little different: cooler temperatures, more light, less water. It does take time to master this species. Simply put, remember these tips: Spring to Fall give adequate amounts of water, fertilizer and light. Fall to winter give cooler temperatures (especially at night), water SPARINGLY to prevent them from drying out, keep on dry side.

Overwatering this orchid will only induce growth and will prevent it from flowering. This dormancy period is crucial. Sometimes the best advice one can give is just forget about your plant during these months of dormancy. You may think the plant has died and may be tempted to discard it. Be patient and diligent with their extreme care requirements and you will be rewarded with gorgeous inflorescences.

Good luck!

Until next time,

Vivi

P.S. Summer is here and insects are active during this time. Check your plants, leaves for pests. Remove old dried sheathing to prevent scales from forming. Any infestation is hard to rid so take a few extra minutes each week to monitor your plants' health.