Unfortunately if you're in an area like mine there really aren't many green things... But right this second we have no snow and so...I'll take that.
Recently I've strained and started regular use of some of my wild crafted herbal tonics, tinctures, and infusions. I've foraged in some sort my entire life. As a child I gathered the raspberries and blackberries that ran wild over my parent's 50 acres. I would eat the sweet red clover tops and pull the potent wild garlic from the earth. Stained my hands on the mulberries as I pulled the sweet gems from the trees.... I'm sure many have foraged at some point if you think about it.
As I got older and realized the vast amount of wild things that we could use either for food or our own medicines I strove to expand my skills beyond the 'basics'. There are two items, often found and unwanted, in our very yards. Plantain and Dandelion both have wonderful healing abilities and yet are considered weeds by many.
Driving down any country road in the late summer we can see Goldenrod (often mistaken for the green allergy aggravating Ragweed), Mullein, Meadowsweet, Yarrow... the list goes on and yet we've forgotten how to utilize them.
And so, I set to educate myself.
There are many books and websites on the subject of edible and medicinal wild things. I strongly suggest to read whatever you can get your hands on, old books, new books, websites... you can glean helpful bits from them all.
I recommend picking an herb a week to completely familiarize yourself with. Learn their common name(s), botanical name, what parts are used, how to harvest them, their constituents, energies, taste, preparations, and dosage and safety.
Don't for one second believe that just because something is from nature that it's safe. Always familiarize yourself with any safety recommendations.
If possible, forage or even buy a small amount to see, touch, and smell in person. If I cannot forage it, or I run out, I purchase extras from Mountain Rose Herbs. I trust them, their prices and shipping are top notch.
The world of herbalism is vast. There is so much to learn that you have no worries of it concluding. You can even involve your family, children love to immerse themselves in the outdoors.
So next time you go for a walk, keep your eyes open. You could have a veritable herbal goldmine right outside your door.