Several years ago I decided I wanted an Elder tree. Here is some of what she has taught me...
She's extremely hardy, takes root anywhere - even in a pot of water. She will take over your yard, your house, your mind, lol. She grows like a weed and can withstand most hardships. She's an extremely fast grower (from a 6-inch cutting to taller than I am within one year). She attracts spiders and her roots run deep.
There is a ton of folklore revolving around the Elder tree. Folklore wasn't made up because people were bored and needed a bed-time story, so where there's folklore, there's been "the folk" IMO.
In folklore she's much related to divinity, and even if one doesn't work with divinity that still implies, since she's a tree and has deep and invasive roots, that she is a gateway to the otherworld (or underworld as most divinities attached to her are underworld divinities). Whether or not one believes in divinity doesn't change the fact that the folk DID believe, so the lore of the associated plants and divinities will reflect the plant's associations and uses. Back in the day she was a revered tree, people would not kill an Elder tree. So I take that to mean she was viewed as a tree of great power, connection, and even revenge/temper. Her berries will heal (as being an ex-smoker prone to bronchitus I can attest they are the best for keeping me away from the doctor's office) and her leaves can harm. Her wood is often used to make whistles, and whistles in folklore have been used to call things. Her flowers can be a healing tea for colds and can also be used for remembering, for seeing what she has seen (see HCA folklore/fairytales). I find the tea very nice prior to scrying/thinking. Working on some problem and getting advice from someone "who's seen it all before."
Her mother from whom I took the cuttings was a wild tree, but my Elders have lived in my yard and been more influenced by human closeness. But I've worked with them daily so their spirit doesn't recede from my contact. Her roots go down into the underworld, and she can lead one home. She is a tree of connection/memory, to the ancestors (not specifically DNA, but the folk ancestors, memories, "witches" (although I dislike that term). She is very protective if you have a relationship with her, and she is extremely protective of children. I have found her to be forgiving, depending on your level of ability, but not to the point of accepting stupidity and laziness and self-pity. One of the commonest answers I get from her is "well, what are YOU going to do about this?" and then she will help, but only if I am willing to get up of my ass and take action, lol. I've learned how to decipher her reactions based on my location - which movements are yes or no, or do what you want, lol.
She's taken over much of my yard, now, and I have agreed that she may but that I have to keep the walkways clear. Most of that is my fault as I removed her from her natural habitat and brought her to my yard, where I tried to bend her to my will and make her live nicely and tamely in the designated area. And I found out she doesn't put up with that shit, lol. She isn't tame, she won't change who and what she is to suit my needs. She'll give you a straight answer, even if it ruins your plans for a nice neat yard. So don't ask her if you don't really want to know and you aren't going to listen. She's not tame - but she'll work with you, if she agrees to and you hold up your end of the agreement. And that right there has taught me much of working with other things... I can't change or tame them, but if I hold up my end and do what I've said I will some of the things are willing to work with that. Go back on my word, miss a few weekends of tending her, and the whole yard's turned into a forest, into chaos. Like any untended relationship, magical or mundane. She needs room, she won't be contained or confined, and I must hold up my end of the bargain - it is reciprical.
I've also found that if you spend enough time with her you start to be more like her. You don't put up with bullshit, and you have high expectations of others to keep their word. And if they don't you loose all interest in them. And she expects communication. You can't totter off and come back in 4 months and say "life got busy". If you're going to be away, you best tell her why and it best be a good excuse.
She taught me to start at home. That if I want to build a relationship with the spirit-world and the things in it, tend first to myself and what I am responsible for. It's fake to go save the wales when everything in your own garden and your relationship with it is dying of neglect. You'll come home and find weeds and chaos. Not only that, you'll feel empty like the dead branches she's dropped which have died and lost their inner pith. You'll look whole from the outside but inside you will have no anchor. She's taught me common sense. Sometimes a branch will die for some reason and she'll just drop it. She doesn't spend all her energy trying to save what isn't working out. She accepts it and gets rid of it. And she eats it. It decays and turns into mush which I assume becomes fertilizer. She's not big into wasting anything.
But she can also be kind and protective - I've found animals love her. The cats rest in her shade, birds eat her berries, bees and flies pollinate her flowers. Spiders (much indicative of magic) find much to eat in their webs spun between her magical branches. So she's friends to the quiet things that live in peace with her, in a mutual relationship with her. She makes flowers that feed the flies that feed the spiders and pollinate the flowers that make the berries that the birds eat that nest and live and die nearby and feed the ground which she eats.... I found some broken bird's eggs under her, their yolk soaking into the soil. To become her food as she is the food for the birds. She's taught me there is always a price, and always something given for something taken. But in the end I'm all ultimately a part of everything anyway.
I have much more to learn of her yet, her magic, her healing, her anger, her spirit. But that's what I've learned in the last two years or so.... for me the ultimate tree for all needs. In a pinch, whether looking for protection, or cursing, or someone to talk to, she pretty much does it all. I suppose that's another reason she's been considered a witch's tree by the folk.... (and poor J clicked on this and thought "damn - a bloody mile-long post, lmao)