Question
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Followup To
Question -
My big oncidium has two long new spikes - going to bloom for the second time even tho the plant is 5+ years old.  The ends of the leaves get rusted.  I trimmed off the rust part, but it comes back.  What am I doing wrong?
Answer -
Hello Ardie,

Second blooming in 5+ years?  My, you are very patient!  (grin)  One of my bigger oncidiums produces bloom spikes 3 to 4 times a year, at this moment it has 14 spikes!  Of course, it completely fills a 12 inch pot and needs to be divided soon.  

By rust, do you mean the leaf tips turn brown along with some small brown or black spots?  Small brown/black spots is not unusual with oncidiums, I wouldn't worry about them for now.  Browning leaf tips is usually an indication that your water may be high in salts.  Or, if you have a water softener, the presence of salt due to the softening process.  You can help minimize the leaf tip browning by watering twice, once a month.  By this I mean water it in the morning, wait about 2-3 hours then water it again.  The first watering will dissolve the salts building up in the potting mix and the second watering will flush it out.  

Another possibility may be the fertilizer you are using, if you are feeding it one.  Most oncidiums prefer being fed lightly or less than the amount listed on the fertilizer container instructions.  If you are feeding it the recommended amount with each watering, that could easily cause the leaf tip problem.  I feed my orchids with each watering but at 1/4 to 1/2 the recommended amount.  

By the way, where have you been growing the oncidium?  Oncidiums prefer fairly bright light, enough so the leaves will be a light green color.  If yours are more a dark green color, that would mean too much shade.  Move it slowly towards higher light.  

Hope this helps.  Good luck and good growing.

Jim Kawasaki
San Jose, Ca.  

Answer
Hi Ardie,

Thanks for the rating and comments.  I noticed you mentioned having a cymbidium orchid along with the oncidium.  Even though you didn't ask about it, here are some things that might help you with the cym.  You didn't mention where you live or where and how you have been growing your orchids, but here are some general guidelines that my help.  

Cymbidiums require quite a bit of sunlight in order to grow and bloom, even more than your oncidium.  Cyms should be grown outdoors as much as possible.  Cym. leaves will be a light to medium-light green color when grown under ideal light conditiions.  They are for the most part fairly temperature tolerant, easily withstanding temperatures from 40F to 85F, even lower and higher with a little help.  Allow the potting mix to become barely moist between waterings as cyms do not like to have their roots constantly wet.  If possible, humidity should be above 50%.  Place it where there are some gentle breezes or, if you have it in your home, have a small oscillating fan to help create air movement around it.  You can feed it with the same orchid fertilizer as the oncidium at the same reduced amount I had suggested earilier.  

Hope this helps.  Good luck and good growing.

Jim