all plants shed the oldest leaves.. its usually seasonal.. and annual ...

i cant quite tell how long youve had this plant... so there might be stresses of moving locations.. light changes... watering changes.. etc ...

soo.... study leaf age.. just remove oldest.. usually lowest or outer most.. and see if that doesnt make it look better ..

also note the newest leaf or two;.. those are what is telling you current situation.. rather than some stress that might have happened weeks or months ago ...

ken

Thank you, Al and Ken. I've had the plant 1 month and this just began. The nursery had these under a sun-filtering carp. I have it on a console in front of a full-wall open window that leads to a balcony with overhead roof, where It receives lots of light but no direct sunlight.

I water the plant weekly, when the surface soil is completely dry to an inch and have not yet applied any form of fertilizers. I did water in a tsp of meal frass as a top dressing 1x when I brought it home. When watering, I do flush the pot to runoff and allow it to drain in the sink. I also do tip my pots to remove any stagnant water. Note I live near the beach in a tropical climate with extremely high heat and humidity.

I have other prayer plants and posted to learn more about the needs of this plant in particular. Not only are the leaves browning in spots, this past week it has not been lifting or 'praying' when the sun begins to go down. Until now it was doing so. This tells me it's in distress.

Two things come to mind. First, I have a tendency to leave new plants in their original pot/medium the 1st month or 2 as they acclimate to their new environment. Perhaps it's time to change the soil to inspect the root system and make sure it's not trapped in one of those horrid 'grow plugs'. Second, I haven't been able to collect rain water lately for my indoor plants and have been using tap water. All are doing well except this one. Perhaps this plant is particularly sensitive and can only tolerate rain water.

M - as dedicated as you are to ensuring your plants are healthy, you might want to consider purchasing a small R/O water filtration system. I have a 5-stage system that can produce about 75 gallons of R/O water per day, and systems that produce 100, 150, or 200 gallons per day. The 75 G/D system is more than enough to filter water for all our drinking and plant needs. I paid about $200 for mine about 10 years ago, and it's currently about $280. It produces water with 0 ppm dissolved solids, so almost all intents/purposes, it's the equal of distilled water and should have a lower level of dissolved solids than rain. See Here

The systems are very easy/quick to install and require only simple tools.

Al

Im going against the grain here - this is a calathea and they like more water than the average houseplant. Keep the soil moist, but not wet. They also like a lot of humidity. You can place rocks on a plate with some water and sit your plant on top of the rocks, or put it by a humidifier.

You're not really cutting against the grain at all. "Moist but not wet" is typically what nearly all houseplants prefer insofar as moisture levels in the root zone are concerned, so in that regard they aren't any different than most houseplants. They do like humidity levels of at least 50%, preferably higher. They also don't deal with perched water any better than other foliage plants.

As an experiment I put together a large humidity tray filled with peastone and filled it with water so the entire surface of the pebbles was wet. I placed a bonsai tree on blocks immediately above the tray - maybe 1/2" of separation and wedged a digital hygrometer in the branches. Imagine the setup below except the tray would be much larger and filled with peastone/water.

The humidity tray raised R/H only .4% (four tenths of 1 percent); so, most rooms will have much too much buffering capacity to allow a single humidity tray to make any meaningful difference in humidity levels in the plant's immediate proximity. It would take a good number of humidity trays in most rooms, or a humidifier (far more effective) to move the R/H level meaningfully.

Al

The humidity tray raised R/H only .4% (four tenths of 1 percent); so, most rooms will have much too much buffering capacity to allow a single humidity tray to make any meaningful difference in humidity levels in the plant's immediate proximity. It would take a good number of humidity trays in most rooms, or a humidifier (far more effective) to move the R/H level meaningfully.

Very useful. I think I will no longer keep a container of water next to my orchids.

We own a retail plant store and keep our humidity somewhere about 65% most of the time, I find that even at 65%, our calatheas still don't thrive like they would in a greenhouse setting. We find small amounts of water more often rather than big amounts of water less often to be more beneficial to our calatheas though. We throw the "let the top dry before watering again" out the window with calathea, begonia, stromanthe, and some others because if we wait that long we get browining/crispy leaves.

Watering in small sips ensures dissolved solids from fertilizer solutions and tap water don't get flushed from the soil, so they build to levels that affect the plant's ability to keep its most distal parts hydrated. It also tends to quickly skew nutrient ratios in the soil/ soil solution, which can quickly cause antagonistic deficiencies, depending on what fertilizer is used. At a minimum, it will cause a build-up of (bi)carbonates. So, while that might be a useful strategy for plants that come and go, it's not the best long term strategy.

I agree the oft repeated advice to water when the soil is dry to the second knuckle, and similar, is more often than not poor advice, but mostly because it promotes over-watering unless the pot is about 5" deep or less.

Al

Well, the last leaf just fell off this one, so it may be a goner. I'll place the pot on my 'triage table' and watch for new growth just in case but am skeptical. I have another similar wider leaf calathea that's doing great.

I'm in the Caribbean so humidity is very high and not an issue. I am also surrounded by beach, so the corrosive salt air is always a consideration. I used only rainwater after posting this and that made no difference. Since it's indoors, watering was every 7 to 10 days, depending on ambient temperatures and when the top 1'' of soil was dry. I NEVER water anything in 'small sips' ... I water to runoff and tip / bounce the pot to drain excess. I have had this plant 3 months and have only applied 1 tsp earthworm castings as a top dressing on month 2. There is no mineral buildup.