New Onc Carnival Costume - Sunburned?

[taradale]

I rec'd an Oncidium Carnival Costume and Colemanara Wildcat Bobcat yesterday in the mail. Well the Onc Carnival doesn't look right, parts of the leaves are all bown/red on it and what look likes bubble scars. I didn't look at the leaves too closely yesterday, because I was bummed that both the Carnival & Bobcat's spikes had been damaged during the mailing (The dark side of mail order) and I also wanted to get to my task of DE dusting my sick snail ridden Vuyl Cambria.

Well this morning, when I was tending to my orchids I noticed the brown/red leaves. Is this something that could have happend in less than 24hrs. I had the Onc in shady part of the basket so it's mystery to me if the bright light alone could have caused this? I even placed her at a funky angle to keep her out of direct sunlight.

Below is the set up and the Onc Carnival is in the lower basket and close-ups of the areas affected.

Also, while I'm thinking this through, the Vuyls nor the Colemanara have any evidence of this mystery burn? If that what it is.

Any opinions, advice and experience greatly appreciated.

Thanks!!
Kath-

[jerrymeola]

What you are seeing is very common in oncidium alliance plants.

I have this often with my orchids. The tips of leaves turn burn and entire leaves fall off. It is the result of heat and stress (or just age) but not burn. Sunburn on an oncidium will show up in the middle of a leaf not the tips usually where the leaf bends.

With our heat here in Florida every leaf on my oncidiums can look like this in August. If they look really bad I cure it with a pair of scissors and cut them off. Once new growth, has started I tend to ignore the old growth. Overly stressed plants can lose every leaf. I always judge the heath of a plant by the new growth not the old leaves.

Newly arrived plants will often lose leaves. The stress of shipping and the change of environment add to the problem. I notice a lot of roots outside the pot. This is common with oncidiums grown in greenhouses. They grow very fast. In the greenhouse they got watered probably every day and the roots did well as bare root. The change to your watering will kill back some of these (it is not a problem and can not be helped). I have the same issue with new plants especially if I mounted them and totally changed their method of growth.

After the flowers are finished you will see a lot of new growth. The new growth will be adapted to your growing conditions.

[taradale]

Jerry,
Thank you so much.

Kath-

[Cynthia, Prescott, AZ]

Are you sure it was not this color on arrival. It looks kind of like high light effects, which is not a problem. If it continues to change color, that would be a problem. If it is steady state, don't worry. Cynthia, Prescott, AZ

[taradale]

I honestly can't remember if that was the color on arrival. But, the more I think about it - it had to be because I put it out in the basket after the 45mins of afternoon full sun that that particular area gets. And since he was brand new i made sure to stick him on the shady side of the basket. Then I noticed the unusual red/brown color the following morning, before it would have gotten any sun.

Thanks again for the great advice and helping me determine whether this was defective plant or not. It was new seller for me.

I'm planning on leaving it alone and not cutting the leaves or anything, they don't bother me. I just wanted to make sure it wasn't diseased or something. Especially because of the bubble scars on it.

Kath-

[jerrymeola]

If you look closely at the leaves of an oncidium alliance plant you will see a thin line at the top of the bulb where the leaf starts to grow. This is the point where the plant can disconnect the leaf from the bulb. It comes off as a clean cut.

These plants discard so many leaves they have evolved an easy method to trim themselves. The leaf becomes totally brown and falls off. The bulb continues to look the same an acts as a food and water reservoir for the plant.

[frances]

I'm sending you a very good article about heat stress from the American Orchid Asociation, it's been very helpful for me, cause I live in a very hot climate all year long, so I hope that you take a lot of knowledge from it.
Good Luck

ORCHID AILMENTS
Heat Stress By Susan Jones
Getting Your Orchids Ready for the Summer Sun
LIKE PEOPLE, ORCHIDS, ESPECIALLY those that prefer cooler, shadier
environments, can suffer from heat stress during the hot summer months.
The midday sun is intense, especially during the summer, and the high
temperatures that bright sunshine brings can burn your orchids quickly,
especially the more sensitive types such as phalaenopsis, pleurothallids,
paphiopedilums and miltonias. Heat stress is a condition that occurs in orchids and other plants when excessive heat causes an imbalance in transpiration, the process by which moisture evaporates from the plant’s tissues. When that rate of evaporation exceeds the pace at which moisture is being replaced through water taken up by the orchid’s roots, the plant becomes dehydrated — leaves soft and wilted, pseudobulbs wrinkled and ridged. The instinctive response in this situation is to overwater the orchid to correct the dehydration. This can instead make matters worse by rotting the plant’s root system, further hampering its ability to take in much-needed
hydration. The roots can only absorb so much water at one time. In addition
to watering, control of heat and humidity play a significant role in the prevention and management of heat stress.
SIGNS OF HEAT STRESS
These symptoms may appear singly, even in otherwise fairly healthy orchids. When they appear in combination, however, it is usually an indication of heat stress or an underlying problem (such as root loss) that has lead to heat stress. Yellowing of Plants and Leaves Too much light causes a plant’s chlorophyll to deteriorate, which can turn your orchid an anemic yellow-green, and eventually cause premature loss of leaves. Most healthy orchids receiving appropriate light levels will be a robust
light green. Withered Leaves The culprit, especially in summer weather, can be overheating. If your plant’s leaves feel warm to the touch, they could be
getting too much light, and need increased air circulation and shading, or a move to a more p r o t e c t e d area.
Sunburn
Initial signs of sunburn, as in humans, appear as a reddish-purple tint or freckles on leaves and pseudobulbs. In advanced stages, leaf tips and roots may brown, flowers drop, buds blast or flower spikes fail altogether.
Shriveled Pseudobulbs
Your orchid’s pseudobulbs serve as its water-storage organs, so shriveled pseudobulbs indicate a dehydrated orchid – it is in a stressed state, having used up its moisture reserves.
Leathery Leaves
This goes beyond mere wilting, and occurs in the advanced stages of heat stress, indicating severe desiccation and possible damage on the cellular level.
Depending on how long the condition has persisted, the type of orchid and
its overall health aside from the leaf damage, it may or may not recover once
its leaves are parched.
PREVENTION
Your orchids need lots of attention during the summer months, especially on hot days. With higher temperatures, orchids require more frequent watering to prevent dehydration. High temperatures quickly dry out mounted orchids, those in baskets and even potted plants. Maintaining the balance between
keeping orchids sufficiently hydrated and over-watering can be a challenge. A simple rule of thumb is that an orchid’s need for water increases and decreases with the ambient temperature, so water thoroughly and more frequently during higher temperatures. Most mounted plants and those in baskets, especially vandaceous orchids and other genera grown with little or no media, will benefit from daily watering in warmer weather. In addition, keep humidity high and air movement continuous, as both of these factors help plants keep their cool on hot days. Adding a fan to the growing area, or locating your orchids where they receive the caress of summer’s breezes, as well as spacing your plants to allow for sufficient air circulation between orchids, can make a big difference in their environment and overall health. This will also help to keep rots from fungi and bacteria at bay.The benefits from misting orchids during hot weather do not have much sustained effect, so unless one has a misting system in place to maintain that added humidity throughout the day, it is probably not useful to your plants. When watering or misting, always be certain that plants have ample time to dry before night falls, so as to discourage bacterial and fungal growth. hen moving orchids outside for he season, start them out in a shaded spot and gradually increase their exposure to sunlight to acclimate them to the higher outdoor light levels. Make sure to protect them from the strongest sunlight as midday summer sun has more intense UV rays that can burn tender plants. Check the amount of exposure your plants receive at different times during the day as the sun moves, and throughout the year as the earth’s orbit around the sun
makes its gradual seasonal changes, which in turn changes the angle of the
exposure your plants receive. For greenhouse growers, consider using shade cloth for added protection during the summer months. Windowsill growers may want to add a sheer curtain during the summertime to keep sunlight reflected by the window glass from causing sunburn. Finally, always have someone care for your orchids while you are away on summer vacation.
TREATMENT
Once an orchid has suffered the effects of heat stress, it may take a long time to rebound. Apply fertilizers sparingly, using a weak solution, and flush the growing medium with clean water between applications of fertilizer, as the salts in fertilizers are difficult for dehydrated plants to assimilate, and a regular dose may further burn the plant. Be especially alert for pests on distressed orchids – insects and viruses are more likely to attack weakened plants.