Sudden change in two orchids, is it sunburn?

[AEKass]

I have had these two orchids for several (5+) years and have had them in the same spot (near south facing windows) for the past two years. Recently I noticed discoloration on both orchids. We typically keep our blinds up all the time, but since this was a sudden change and I have not changed their location, watering or feeding in years I am unsure. The weather has recently changed where I live (Chicago), but I have a humidifier that I use when it is very dry. I cut spikes off of both orchids within the last 2-3 months after all the flowers died. I water the plants by putting them under running water, putting the faucet in spray mode, and typically water in the morning. Based on similar posts on the message board I think this is sunburn, but I'm not totally sure. If it is sunburn, I'm unclear on why it suddenly happened and what to do going forward to keep my plants healthy.

In the larger orchid I noticed one side of its center suddenly became very light, as did a spot on one leaf. The discoloration seems to be worsening, but it is also producing a new leaf (just saw that today). The leaves also seem a bit parched.

In the smaller orchid, an older leaf was turning yellow and I wasn't concerned at first. However, recently several other older leaves (~4) have started turning yellow with some black spots. The black spots seem like sunburn, but I'm unsure. I took the photos of the smaller plant shortly after watering.

Appreciate any thoughts! And please let me know if I should provide more information or different photos. Thanks!

[Dollythehun]

A couple pictures do look sunburned, others I am unsure of. We have had weird weather but, not exceptionally sunny or hot. How does Chicago water test, PH, TDS, trace minerals? We have well water and I had neutrient defficencies in my phals, which took years to show up. I've been growing them a long while but still think I'm a novice. Someone will be along soon to help further.

[AEKass]

Thanks Dollythehun for the feedback! I'm not too sure about Chicago's water, but the city does post information on that online (City of Chicago :: Water Quality Results and Reports).

I haven't looked at the reports yet, but will shortly. What in particular should I look for? What would indicate water quality is an issue?

[ryrycochinco]

The white spots definitely look like sun bleaching

[Dollythehun]

I am just sure I will get corrected here, however, I noticed some of those blemishes on my phals. Brown crunchy leaf tips and foliage with yellow streaks and spots. (Look at the St.Augustine Orchid site). I was underwatering and my water binds up minerals. I switched to Repotme.com's Imperial phal mix and added cal-mag. I also started filtering my water. The symptoms eventually went away and my phals went into a growth spurt. My eyes glaze over when the experts start talking water...but, there was a connection with mine. Chicago's water comes from the Lake vs my well water, however I'm only 5 miles from the lake. So that may not be your problem. Take my thoughts for what they are worth.
All that to say, there may be more than one problem.

[Roberta]

In both spring and fall there can be sudden changes of sun when the sun clears a building or other obstacle. This can toast leaves even if it isn't particularly hot in general... A sudden blast of sun for 5 minutes can do that... and then it passes as the sun moves, if you aren't standing there to see it, won't be obvious at all why it happened. I speak from hard experience...

[AEKass]

Thank you Roberta! Is there anything I should do now to keep them healthy? I did start putting the blinds down to prevent further sunburn.

[Roberta]

Originally Posted by AEKass

Thank you Roberta! Is there anything I should do now to keep them healthy? I did start putting the blinds down to prevent further sunburn.

They should be OK. The toasted leaves won't heal, but won't hurt anything either... if they turn brown and crispy can be trimmed, but don't rush to surgery.

A concern now is that they don't get ENOUGH light... with Phals I have found that supplemental light from fluorescent (LED should work too) lamp 12 hours a day helps blooming. They need long duration of gentle light.

[estación seca]

The sun is lowering and trees are losing leaves. The sun enters your windows at a lower angle and penetrates farther into the room. Spring and fall are big sunburn seasons for Midwestern plant growers.

Also be sure you don't have spider mites. Run a white tissue under the leaves and look for brown or red streaks. If you have those, spray the upper and lower surfaces of all your leaves with 70% rubbing alcohol or 1 teaspoon of liquid dish detergent in a quart of water, and report back here for more advice.

[AEKass]

Hi All:

Based on everyone's feedback, I think it is just sunburn, but I wanted to post an updated photo of the most affected leaf. The spot has become more brown (and thin), but the discoloration does not seem to have spread.