Liquorice Root
I settled on this, because it has a strong historic record of being used + is commercially availiable.
Advertisement said Also known as 'jethi mudh' or 'malethi' (Jalpur brand)
Wikipedia said that salted liquorice was a good idea
Some long-term health effects, but probably ok.

Apple
"Tree bark is used to treat fevers and diarrhea."
https://www.offthegridnews.com/alternative-health/10-medicinal-trees-that-heal-virtually-everything/

Hazelnut Tree
"The bark was made into a poultice to help close and heal wounds.  The casing on the outside of the nuts was used to expel worms and parasites."
https://practicalselfreliance.com/medicinal-trees/

Oak Tree
"The tannins in oak bark and leaves can help disinfect wounds, and the tannins supposedly work to strengthen blood vessels.  It’s commonly used as a gargle for bleeding gums and a wash for hemorrhoids."
"It’s also been used against worms and parasites."
https://practicalselfreliance.com/medicinal-trees/
"The bark of oak is used for a range of medical treatments. White oak bark, in particular, is useful when it is converted into a tea that is then applied to bronchitis, caught, fever, colds, arthritis, and diarrhea. Oak is also applicable to the digestive tracts. Here, it is known that it can be used to stimulate appetite and even improve digestion for those who use it."
https://survivalistknowledge.com/common-trees-with-important-medicinal-uses/
"Oak is excellent for controlling loose stools. Either a tincture (alcohol extract) or decoction (boiled tea) of root bark is effective. Decoctions are used to promote healing of bleeding gums when used as a mouthwash. Finely powdered dried inner bark has been used to control nosebleeds. Oak is said to relieve poor digestion. It has been used to treat ulcers internally and externally. Finely powdered dried inner bark can be sprinkled on external ulcers to soothe, reduce swelling, prevent infection and strengthen tissue. A decoction or tincture can be used to heal internal ulcers. Compresses made from a root bark decoction soothe and shrink hemorrhoids, varicose veins and bruises. A bark decoction can be used as a gargle to relieve a sore throat. Skin problems such as rashes, irritation and swelling may be relieved with the application of poultices or compresses made from the root bark or leaves. Oak has been used in the treatment of cholera and gonorrhea. Decoctions have been used as douches to treat vaginal infections"
https://www.offthegridnews.com/alternative-health/the-natural-healing-power-of-oak-trees-and-acorns/
"The leaves and acorns of the oak tree are poisonous to cattle, horses, sheep, and goats in large amounts due to the toxin tannic acid, and cause kidney damage and gastroenteritis. Symptoms of poisoning include lack of appetite, depression, constipation, diarrhea (which may contain blood), blood in urine, and colic. The exception to livestock and oak toxicity is the domestic pig, which may be fed entirely on acorns in the right conditions, and has traditionally been pastured in oak woodlands (such as the Spanish dehesa and the English system of pannage) for hundreds of years.
Acorns are also edible to humans, after leaching of the tannins"
https://en.wikipedia.org/wiki/Oak

Willow
"A natural precursor to aspirin, willow bark was harvested by native Americans to treat pain and fevers.  Willow bark is also used externally to treat wounds."
https://practicalselfreliance.com/medicinal-trees/
"Plant source of salicylic acid, white willow is like the chemical known as aspirin, although more likely to cause stomach upset as a side effect than aspirin itself which can cause the lining in your stomach to be destroyed."
https://en.wikipedia.org/wiki/List_of_plants_used_in_herbalism
"The bark of the willow has been known as a powerful medicine for more than two millennia. In many ways, it is the true precursor or aspirin and its use helps with headaches, menstrual cramps, gout, and osteoarthritis. Modern medicine has been inspired by willow bark by such a measure that many still see aspirin as something that would have been impossible without this simple yet extraordinary tree."
https://survivalistknowledge.com/common-trees-with-important-medicinal-uses/
"The leaves and bark of the willow tree have been mentioned in ancient texts from Assyria, Sumer and Egypt[citation needed] as a remedy for aches and fever,[17] and in Ancient Greece the physician Hippocrates wrote about its medicinal properties in the fifth century BC. Native Americans across the Americas relied on it as a staple of their medical treatments. It provides temporary pain relief. Salicin is metabolized into salicylic acid in the human body, and is a precursor of aspirin.[18] In 1763, its medicinal properties were observed by the Reverend Edward Stone in England. He notified the Royal Society, which published his findings. The active extract of the bark, called salicin, was isolated to its crystalline form in 1828 by Henri Leroux, a French pharmacist, and Raffaele Piria, an Italian chemist, who then succeeded in separating out the compound in its pure state. In 1897, Felix Hoffmann created a synthetically altered version of salicin (in his case derived from the Spiraea plant), which caused less digestive upset than pure salicylic acid. The new drug, formally acetylsalicylic acid, was named Aspirin by Hoffmann's employer Bayer AG. This gave rise to the hugely important class of drugs known as nonsteroidal anti-inflammatory drugs (NSAIDs). "

Silver Birch
"Birch bark is antibacterial, and it was used to create storage containers that helped keep food from spoiling."
"Its also been used to treat gout, kidney stones and scurvy"
https://practicalselfreliance.com/medicinal-trees/
"Leaf tea helps heal sores in the mouth and helps heal bladder and kidney problems, and gout. Use bark in a bath to aid psoriasis, skin rashes and eczema. Birch sap contains betulinic acid, which is used to help reduce tumors and fight cancer."
https://www.offthegridnews.com/alternative-health/10-medicinal-trees-that-heal-virtually-everything/
"They are loaded with vitamin C and are in fact employed in many pharmaceutical products. When used as a boiled and drained tea, birch can do a lot of good in the case of urinary infections that impact the bladder, kidneys, urethra, and ureters. Additionally, its diuretic properties are regularly employed to increase the output of urine."
https://survivalistknowledge.com/common-trees-with-important-medicinal-uses/
"Native to northern and eastern North America, birch trees possess concentrations of salicylic acid, the predecessor of aspirin. Although birch products were never widely used, folk medicine called for chewing birch twigs to relieve headache and pain. Willows (Salix spp.) also contain the pain-reducing acid."
https://www.woodmagazine.com/materials-guide/lumber/medicinal-trees

Walnut
"Medically, walnuts are a well known purgative which helps to cleanse the body of parasites."
https://practicalselfreliance.com/medicinal-trees/
"The leaves of this tree are anti-inflammatory, alternative and anthelmintic. Internally, they are applied to issues like constipation, diarrhea, asthma and chronic coughs."
https://survivalistknowledge.com/common-trees-with-important-medicinal-uses/


Bitter Orange
"Used in traditional Chinese medicine and by indigenous peoples of the Amazon for nausea, indigestion and constipation."
https://en.wikipedia.org/wiki/List_of_plants_used_in_herbalism

Trifolate Orange
"Fruits of Citrus trifoliata are widely used in Oriental medicine as a treatment for allergic inflammation."
https://en.wikipedia.org/wiki/List_of_plants_used_in_herbalism