Oncidium undulatum is a strong-growing evergreen species, and it belongs to 
the O. macranthum section. The scape is produced from the side of the bulb 
after growth is matured, and, like all this section, it is a very long time between 
its first appearance and the development of its flowers. The sepals are brown, 
flushed with green- in the centre, petals white, having a large irregularly shaped 
blotch of purple at the base, and spotted with brownish purple on the upper 
margins; lip wholly rich purple. It blooms during the months of March and April, 
and continues in full beauty for about six weeks. 
This species requires similar treatment to that of Oncidium macranthum, 
revelling in the cool moist atmosphere of the Odontoglossum house, as do all the 
kinds from the cool regions of Colombia. There are also some fine kinds from the 
cool regions of Brazil that thrive under the same conditions, and thus become good 
companions, while as their flowers in many instances differ in colour from those of 
0. undulatum, O. macranthum, ete., they afford excellent contrasts. The plant now 
under consideration should be grown in good fibrous peat and living sphagnum moss, 
and the pot must be well drained. As before remarked, it is a strong-growing 
plant, and it produces roots in abundance. It requires a liberal supply of water 
during the growing period, and should not be allowed to get dry at any season, 
but during the winter months the quantity must be reduced considerably, just 
sufficient being given to keep the bulbs and leaves in a good healthy condition. 
Nothing is more inimical than shrivelling of the bulbs, to this section of the genus, 
and should it occur, it is a difficult task to restore them to health. With the 
early spring months the scape appears, and at this time the plant requires to be 
watered in a very careful manner; but after it has attained to a foot or more in 
height, water may be given more freely. In ve-potting, care must be exercised 
that the roots do not receive injury, the best time for the operation being just. 
prior to the commencement of new growth. If re-potting is not necessary, with the 
return of spring, any old or exhausted soil should be removed, and substituted by 
new, fresh material, after seeing that the drainage is in good working order. 
This operation must be performed with care, as the plant will receive a decided 
check if its roots are injured in any way. 
