I don't think it was left in the sun, but I'm not sure. The person that took it home to replant may have. Too much sun causes a chemical reaction that releases a powerful oxidase, H2O2/ hydrogen peroxide. H2O2 has an O- free oxygen radical which attacks (oxidizes) the first organic molecules it comes in contact with, which is usually the green pigment (chlorophyll) an essential constituent of the plant's photosynthesizing machinery. Even a half hour in full sun can affect plants not properly acclimated to such a heavy photo load. If you find it WAS left in the sun, that would conveniently explain the symptoms. If it wasn't, damage as shown could also be the result of a sudden over-application of fertilizer, severe over-watering and/or soil compaction. Sudden exposure to chilling temperatures can cause leakage of phenolic compounds into inter-cellular spaces, which can also cause the same symptoms via a different mechanism.
I don't believe there is a drain hole, should one be added? Yes. If the pot has a snap-off bottom, snap it off and make sure there is at least 1 drain hole in the pot that holds the plant. Pots w/o drain holes make it far more difficult for even experienced growers to grow in; this, due to the significantly increased chance of over-watering and the fact that it ensures all salts from tapwater and fertilizer solutions will remain in the grow medium making water/nutrient uptake difficult and skewing the ratio of each nutrient to the others, which causes antagonistic deficiencies even if you DO fertilize regularly. How often should this plant be watered? Plants are best watered on an 'as needed basis'. It's relatively unimportant how dry the top of the soil column is, and very important what moisture levels are deep in the pot, where it counts. If pots are about 5" deep or less, the finger method works - dry to the second knuckle - time to water. For deeper pots, say a plant in a 10" deep pot, the top 3" of the soil can feel dry while the bottom 6" of soil is still 100% saturated. It's that layer of saturated soil that causes watering problems because too much water means too little air in the root zone.
One of the most reliable methods of checking a planting's need for water is using a 'tell' (more reliable than a 'moisture meter'. You can use a bamboo skewer in a pinch, but a wooden dowel rod of about 5/16" (75-85mm) works better. They usually come 48" (120cm) long and can usually be cut in half or in several pieces, depending on how deep your pots are. Sharpen both ends of each tell in a pencil sharpener and slightly blunt the tip so it's about the diameter of the head on a straight pin. Push the wooden tell deep into the soil. Don't worry, it won't harm the root system. If the plant is quite root-bound, you might need to try several places until you find one where you can push it all the way to the pot's bottom. Leave it a few seconds, then withdraw it and inspect the tip for moisture. For most plantings, withhold water until the tell's tip comes out nearly dry. If you see signs of wilting, adjust the interval between waterings so drought stress isn't a recurring issue.
I meant the soil must've been contaminated with some kind of fungus since mushrooms were growing. Fungal spores are ubiquitous and trees even form a symbiotic (mutually beneficial) with many species of fungi. Not much to worry about because only a few species of fungi, usually associated with poor conditions in the root zone, are problematic for plants. Most of those are gathered loosely under the umbrella of 'damping-off diseases'.
We haven't fertilized it, should we? Most hobby growers don't fertilize often enough or at an appropriate rate. Fertilizer packagers provide directions that ensure the most efficient uptake and plant use of fertilizer products, with instructions habitually well within the margins of safe usage practices. I can't imagine they would leave unsaid the recommendation to fertilize at a half or quarter of the suggested rate, yet the advice to do so proliferates.
Regular applications of fertilizer are essential to most plants grown in containers. if the grower wishes to maximize their plants' opportunities at realizing as much of their potential as possible. Withhold fertilizer until you start to see new growth, then fertilize at recommended rates.
Typically, any starter charge of fertilizer a grow medium might contain is only enough to justify the packager using the claim "contains fertilizer" as a selling point. IOW, it might SAY you won't need fertilizer for X number of months, but you'll soon find that most plants exhibit symptoms of deficiencies - especially if you're watering properly.
I use a very good product I highly recommend for a number of reasons. Foliage-Pro 9-3-6 has ALL nutrients (taken up via the root pathway) that plants need for normal growth. The ratio at which the nutrients are provided matches the rate at which the average plant actually USES the nutrients. There is a significant advantage in that, due to the fact it allows you to fertilizer at the lowest concentration possible without deficiencies or toxicities (too much). It also provides more than 2/3 of its nitrogen from nitrate sources, and uses no urea as a source of nitrogen (helps keep plants fuller and more compact.
Al
