help with yellowing phragmipedium leaves

[blipe2]

I am hoping for some help with my phrags. I moved to upstate NY in the summer and this is my first winter growing them under lights. They have all started to get yellowed leaves that are yellowing from the middle outward. I wasn't too worried because they are growing and one is even in bud, but now the new growth leaves are also starting to get yellowed, so now I am worried. They are under a bank of 8 fluorescent lights. I use only RO water. I fertilize about once per month because I was starting to get some blacked tipped leaves when I was fertilizing more often. I run a humidifier during the day. The temp is high 60s during the day and low 60s at night. I thought it might be too cold so I moved them up higher under the lights, only about 8 inches below the middle tube. I am hoping for some thoughts?
thanks

[billc]

Sounds like they are getting too much light. 8 in.below the bulb is kind of close. Are your lights T5, T8 or T12?
I have phrags under 4 bulb T5's with only 2 bulbs in most of the time. The shelf is 24 in below the bulbs and the lights are on 8-9 hours a day.

Bill

[MrHappyRotter]

Summary: Try reducing the light a little, tweak your fertilizer regimen.


I think Bill may be onto something, but without more information about the type of fluorescent lights, it's hard to say. Generally speaking, Phrags do like bright conditions, and many of us grow them bright enough that they develop light green leaves. Some species and hybrids, however, like shadier conditions than others. Do you know the names of your plants? That might help with giving you suggestions.

My color vision is a tad wonky so I'm asking for some clarification as well. To me it looks like the leaves are bleaching out slightly (pale green) on the highest points (mid-leaf) of the wide leaved phrag. That suggests to me that the plant suddenly is getting higher light than it was used to and that the light levels might be a tad intense. I'm really only seeing yellowing leaves in the older leaves of the narrow leaved phrag. And that's perfectly natural. These guys shed old leaves as they grow, and if they're in active growth, then the new roots and new growths are often so rapid that they literally rip off the older leaves at the base of the plant.

Your growing temperatures are cooler than mine (especially your daytime highs), so I don't really have the experience growing Phrags that cool. I imagine they'll do fine, since I know from experience they can handle night-time lows in the low to mid 50s (F). However, cool night temps in the 60s is fine.

If the overall growth color is yellow (which I'm not really seeing in the photos, personally), then it certainly sounds like a nutritional issue. From that perspective, you have to consider whether you're feeding enough, whether you're using balanced fertilizer(s) with appropriate micro-nutrients, and whether there are environmental factors that might prevent some nutrients from being available to the plant.

For feeding, you may want to increase that a bit, so that you're feeding with a weak solution at each watering, and then just be sure to use pure RO water once or twice a month to flush out any excess. Orchids are light feeders in general, but phrags are fast growers, and your potting mix doesn't always supply enough of the right nutrients on its own. You may try to rotate in several different fertilizers (in case any one of them is deficient in certain nutrients). I do this to hedge my bets. I've got proprietary fertilizer, a couple national brand orchid foods (Schultz, Miracle Gro, etc), some Cal-Mag, and then I also supplement with bone meal. I probably go overboard with this, but it doesn't hurt to have a couple different fertilizers on hand. If you're using RO water, then you might want to pick at least one fertilizer that's designed for RO water as well. Also consider what kind of mix you're growing in, and what condition it's in. Some mixes (like bark) end up competing for nutrients at various stages of their life span. Completely inorganic mixes obviously won't provide any supplemental nutrition, so you have to feed constantly with those. Some ingredients can alter the root zone pH, which then changes how readily your plants can absorb some nutrients.

Anyway, just some considerations.

[blipe2]

Thanks for the input. I was wondering the same thing and makes sense. I have them under T8s, but can put them under a bank of 4. I will tweak the fertilization a bit too, was going to add a little calcium supplementation and just got some other fertilizers to try the rotational approach. I haven't done the bone meal, but will also keep that in mind. I appreciate the input.

[estación seca]

MrHappyRotter, the photos definitely show leaves turning quite yellow at the highest parts of their arcs. This is especially noticeable in the photo next to the sink. The yellow patches are mottled with green.

I don't know much about Phrags, but in other kinds of plants I would definitely suspect inadequate nitrogen, iron or magnesium - or a too-high pH, making the mineral nutrients unavailable. In other, nutrient-deficient plants, yellowing often happens on the parts of the plant most exposed to light. The plant struggles to replace chlorophyll damaged in the normal course of exposure to light if it can't get the necessary minerals and nitrogen.

blipe2, yes, Phrags are sensitive to too many dissolved salts in the water, and burn easily. It can take a while for plants to recover from this kind of yellowing since they need to absorb the proper nutrients. Phrags don't tolerate much in the way of dissolved solids in the water.

I would also focus on testing the pH of your water with fertilizer added and making sure it's appropriate for Phrags. You can get pH test kits at aquarium shops. The liquid kits are much more accurate than the dip strips. With the proper pH minerals are absorbed much more readily.

I don't know off hand the best pH for Phrags, but if you use the Search function in the maroon menu above you might be able to find out.