Source of slow release organic nutrients, perhaps?

I've heard of people using teas as a type of low feed fertilizer, maybe this person just went straight to the source and buried the entire tea bag?

The pic is from the Nat'l Bonsai Museum in D.C. Unbelieveably the training was started in 1625.
What looks like tea bags are laying on the surface of the soil. I don't really know that they are tea, could be something else.

I'm pretty sure it's something other than tea or tea bags, unless they're borrowing the bags and perhaps filling them with a nutrient or insecticide (imidicloprid - Merit/Marathon?).

Here's something I wrote a while back about coffee/tea:

Forum discussions frequently center on the question of adding dilute coffee/tea or grounds to plants as a 'tonic', but Arabica (coffee) and Camellia (tea) are known for their toxic alkaloid (caffeine) content and their allelopathic affect on plants as well as autotoxic (poison to their own seedlings) effects on future generations. Caffeine interferes with root development by impairing protein metabolism. This affects activity of an important bio-compound (PPO) and lignification (the process of becoming woody), crucial steps for root formation.
We also know that the tannins in both coffee and tea are known allelopaths (growth inhibitors). There are ongoing experiments to develop herbicides using extracts from both coffee and tea that cause me to want to say they might serve better as a nonselective herbicide than as a tonic. I would not use either (stale coffee or tea) by applying directly to my plants - especially containerized plants; nor would I add tea bags/coffee grounds to my container soils.

Al