A "tell" in the context used is an indicator or a revelation of something hidden. Poker players watch for "tells" from other players to help them make decisions. A fever is a "tell" that the patient is trying to cope with an illness/injury. A completely defoliated plant might be a "tell" there is a root infection or perhaps an abiotic pathogen at work. See below for more re using a "tell".

"Potting Soil" covers a lot of territory. Some commercially prepared potting media are reasonably good and others virtually unusable. I've been growing trees in containers since the early 1980s and I've found that media which hold a lot of excess water (perched water) are generally not a good choice for trees because the excess water limits the oxygen roots need to function normally. It's particle size that primarily determines how much water a medium can hold. The finer the particles that make up the medium, the more water it can hold. If a medium is based on a large fraction of fine ingredients like peat, coir, compost, composted forest products, ....., it's almost certain it well hold enough excess water. Adding more peat to a medium already comprised of a huge fraction of fine materials is a step in the wrong direction because it increases the water-holding ability of a medium that might already be too water-retentive.

I'm guessing you should be able to find a source for pine bark. If you have any interest and think you can find the bark, I can help you make a very good grow medium using the bark + a fraction of commercially prepared potting mix + perlite + lime. It will look like what you see in the middle of this image when dry:

The bark products at 3, 6, 9 o'clock, show an appropriate size bark from 3 different packagers.

If you'd rather not make your own medium, there are some tricks that by using some simple science you can limit the amount of excess water your planting is capable of holding. Since these work passively (no effort on your part other than some easy adjustments at potting time) and very effectively, you get an immense amount of return (some in the form of personal satisfaction) for only a little effort. The 'tricks' I'm talking about can allow you to use a grow medium that without the tricks would be a poor choice. Raise your hand if you're interested.

Using a 'tell'

Over-watering saps vitality and is one of the most common plant assassins, so learning to avoid it is worth the small effort. Plants make and store their own energy source – photosynthate - (sugar/glucose). Functioning roots need energy to drive their metabolic processes, and in order to get it, they use oxygen to burn (oxidize) their food. From this, we can see that terrestrial plants need plenty of air (oxygen) in the soil to drive root function. Many off-the-shelf soils hold too much water and not enough air to support the kind of root health most growers would like to see; and, a healthy root system is a prerequisite to a healthy plant.

Watering in small sips in order to avoid over-watering leads to a residual build-up of dissolved solids (salts) in the soil from tapwater and fertilizer solutions - which limits a plant's ability to absorb water – so watering in sips simply moves us to the other horn of a dilemma and creates another problem that requires resolution. Better, would be to simply adopt a soil that drains well enough to allow watering to beyond the saturation point, so we're flushing the soil of accumulating dissolved solids whenever we water; this, w/o the plant being forced to pay a tax in the form of reduced vitality, due to prolong periods of soil saturation. Sometimes, though, that's not a course we can immediately steer, which makes controlling how often we water a very important factor.

In many cases, we can judge whether or not a planting needs watering by hefting the pot. This is especially true if the pot is made from light material, like plastic, but doesn't work (as) well when the pot is made from heavier material, like clay, or when the size/weight of the pot precludes grabbing it with one hand to judge its weight and gauge the need for water.

Fingers stuck an inch or two into the soil work ok for shallow pots, but not for deep pots. Deep pots might have 3 or more inches of soil that feels totally dry, while the lower several inches of the soil is 100% saturated. Obviously, the lack of oxygen in the root zone situation can wreak havoc with root health and cause the loss of a very notable measure of your plant's potential. Inexpensive watering meters don't even measure moisture levels, they measure electrical conductivity. Clean the tip and insert it into a cup of distilled water and witness the fact it reads 'DRY'.

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.

Al