I've never read about there being a tolerance effect specifically for those two herbs, but in general even with herbs that are super safe for long term use, etc. it's always smart to take a break if you're not experiencing the same beneficial effects, to see if that's what's happening.

The list of herbs that aren't safe to use long term would be very long! I'd grab a couple of herbal medicine books for reference, this is a good one: The Practice of Traditional Western Herbalism: Basic Doctrine, Energetics, and Classification, by Matthew Wood https://www.amazon.com/Practice-Traditional-Western-Herbalism-Classification/dp/1556435037/ref=sr_1_1
(Wood's Earthwise Vol 1 and 2 are also excellent resources.)

You can think of herbs on a spectrum, like:

• Nourishing / tonifying
  
• Mildly sedating / stimulating
  
• Strongly sedating / stimulating
  
• Potentially poisonous
  
  Nourishing herbs like nettle, oatstraw, calendula, red clover, burdock, alfalfa (and many others) are like food, no more harmful to you than eating spinach every day. (Chamomile and lavender may fit into this category, or chamomile might be considered mildly sedating.)
  
  The more stimulating or sedating an herb is, the more you want to pay attention to any potential negatives to long term use.
  
  And of course some herbs are potentially poisonous, but may be good to use on a very limited basis when a strong and fast action is needed. Side effects are common with these herbs. Poke is an example -- it's an excellent herb for combating a strong infection or when you need a quick immune system boost, but you'd only want to take very small amounts (1-2 drops of tincture), and only for a short time period.

Okay so this isn't complete, and apparently my account is too young (or doesn't have enough karma?) to make a post to the subreddit :(

But here is the original post I constructed to submit:

Hello r/herbalism.

This book list was compiled by a good friend of mine who has been a practicing herbalist for a while now. I thought you might all enjoy this list; it's divided into different sections based on the particular area of study. My friend would also like me to inform you "If anyone should have difficulty locating these books, I've found a website, called bookfinder.com, to be most useful in acquiring these books for a fraction of the price from regular booksellers."

Beginner Herbalism, General

• Rosemary Gladstar's Medicinal Herbs: A Beginner's Guide: 33 Healing Herbs to Know, Grow, and Use
  
  
• Making Plant Medicine by Richo Cech
  
  
• Modern Herbal Dispensatory: A Medicine Making Guide
  
  
• Rosemary Gladstar's Herbal Recipes for Vibrant Health
  
  
• Herbal Antibiotics: Natural Alternatives for Treating Drug Resistant Bacteria by Stephen Buhner
  
  
• The Herbal Medicine-Maker's Handbook: A Home Manual by James Green
  
  
• Earthwise Herbal Vol I. and Earthwise Herbal Vol. II by Matthew Wood.
  
  
• The Practice of Traditional Western Herbalism: Basic Doctrine, Energetics, and Classification by Matthew Wood
  
  
  
• Rodale's 21st Century Herbal by Michael Balick
  
  
• The Desktop Guide to Herbal Medicine: The Ultimate Multidisciplinary Reference to the Amazing Realm of Healing Plants in a Quick-Study, One-Stop Guide by Brigitte Mars
  
  
  
• The Herbalist's Way: The Art and Practice of Healing with Plant Medicines by Nancy Phillips, Michael Phillips, and Rosemary Gladstar
  
  
  

  Advanced Herbalism
  

  
  

• Medical Herbalism: The Science Principles and Practices Of Herbal Medicine by David Hoffman
  
  
• Adaptogens: Herbs for Strength, Stamina, and Stress Relief by David Winston
  
  
• Edward E Shook's Elementary Treatise in Herbology and Advanced Treatise in Herbology - (In regards to the second, my friend has found a free PDF of the advanced treatise.)
  
  
• The School of Natural Healing: The Reference Volume on Natural Herbs for the Teacher, Student or Herbal Practitioner by John R. Christopher
  
  
• The Complete Herbal Tutor: A Structured Course to Achieve Professional Expertise by Anne McIntyre
  
  

  Pharmacognosy and Phytochemistry (Part of the Advanced Herbalism List)
  

  
  
  

• The Constituents of Medicinal Plants: An Introduction to the Chemistry and Therapeutics of Herbal Medicine by A. Pengally
  
  
• Phytochemistry and Pharmacy for Practitioners of Botanical Medicine by Eric Yarnell
  
  
• Herbal Constituents: Foundations of Phytochemistry by Lisa Ganora
  
  
  

  Medicinal Mycology
  

  
  

• The Fungal Pharmacy: The Complete Guide to Medicinal Mushrooms and Lichens of North America by Robert Rogers
  
  
• Growing Gourmet and Medicinal Mushrooms by Paul Stamets
  
  
  
  

What about these books?

• Edible Medicinal Plants of Britain and Northern Europe - It's going to be difficult to find a book dedicated solely to plants native to Northern Europe, but once you find a plant you want to study you should be able to look it up in other herbals and such.
  
  
• Northern Plant Lore: A Field Guide to the Ancestral Use of Plants in Northern Europe - I believe this book is pretty good on the subject of Northern medicinal plant information, though there might also be some folklore/magical usage here as well, which is pretty cool if you're into that sorta history and stuff.
  
  
• A Modern Herbal might also be a good resource to check, as many of the plants in it are native to Europe/Britain. It's available online for free as well.
  

Field guides and preparations are generally separate. Peterson's makes an excellent medicinal plants and herbs guide... Amazon

Dosages and preparations require a high degree of cross-referencing, as there is a lot less scientific research in this area (at least that is how I go about it)... Start with foraging around for what is available to you (using a field guide). Then hit up Wikipedia and work your way through the references, look at books on integrative medicine and natural health. Sites like Wikipedia and Web MD, will tell you if there is immediate or significant long term danger of consuming the herb, and give some insight into the alkaloids and active ingredients of most common medicinal herbs... After I pull from places like J-stor, and dive into more esoteric sources like Victorian pharmacopeias and folk lore, and books on ethnobotany etc.

Edit: conservation areas are also a good place to get started, MNR (or whatever the USA version is), and park departments often print little guides to local plants and their history.

For a general overview of the history of traditional herbal medicine in the West, I recommend Barbara Griggs' book, Green Pharmacy: The History and Evolution of Western Herbal Medicine.

For traditional shamanic, magical use of herbal medicinal plants, I suggest you look into the Native American tradition(s). If you are looking for something in the area of psychedelics, I can recommend one book I liked: Cosmic Serpent: DNA and the Origins of Knowledge

For a bend towards energy medicine and the inner practice of herbalism, see Matthew Wood's books, for example The Practice of Traditional Western Herbalism: Basic Doctrine, Energetics, and Classification.

Herbal Medicine Makers Handbook by James Green

​

Buhner is GREAT! What protocol are you on?

​

https://www.amazon.com/gp/product/0895949903/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I've seen this book by James Green recommended quite a lot.

There are plenty of resources in this sub and others already. Poke around and you'll find what you need.

This is a good subreddit. Inactive albeit plenty of good resources available.

If you would like to start hunting for herbs in your area, look for field guides. Peterson's makes some really good ones. Then get your self a few books on herbal information, and a few on preparations.... it is all about the cross-referencing.

I do not know where you live, and field guides need to be geared towards your area....https://www.amazon.ca/Peterson-Medicinal-Eastern-Central-America/dp/0547943989

https://www.amazon.com/Modern-Herbal-Dispensatory-Medicine-Making-Guide/dp/1623170796/ref=asc_df_1623170796/?tag=hyprod-20&linkCode=df0&hvadid=312134205520&hvpos=1o8&hvnetw=g&hvrand=6770824784635939063&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9019656&hvtargid=pla-301634461863&psc=1

Amazing book.

This is a good start...
The Constituents of Medicinal Plants: An Introduction to the Chemistry and Therapeutics of Herbal Medicines https://www.amazon.co.uk/dp/0851998070/ref=cm_sw_r_cp_api_NeJ9BbXCG5JYA

https://www.amazon.com/Rosemary-Gladstars-Medicinal-Herbs-Beginners/dp/1612120059

Get yourself something like this:

https://www.amazon.com/Weeder-Manual-Ergonomic-Garden-Weeding/dp/B07G32YSPJ/ref=sr_1_9?ie=UTF8&qid=1549575887&sr=8-9&keywords=weed+puller

You can obviously use a small spade if you're so inclined, but I found that I more often broke the taproot doing that and got less return for my effort.

Also, while I won't argue with what the other posters have said, harvesting in Spring rather than fall also gets you greens that are less bitter, and fresh flower heads you can use for tea or wine. The greens harvested in Fall are exceptionally bitter and quite unpalatable unless, like me, you've developed a taste for it.